🔙 Quay lại trang tải sách pdf ebook Hóa Đại Cương – Vô Cơ – Tập 2 (Sách đào tạo Dược sỹ đại học) Ebooks Nhóm Zalo DAI CUONG V6 CO I T4p 2 SACH DAO TAO DUQC ST DAI HOC ChU bien: PGS.TSKH. Le Thanh Pht.thc BO YTE' H011 DAI MING - VO Ca TAR 2 SACH DAO TAO DUQC ST DAI HOC Ma s6: D.20.X.05 ChU Wen: PGS.TSKH. LE THANH PHUOC TAN TAO UNIVERSITY LIBRARY NHA XUAT BAN Y HOC HA NOI - 2009 5- 40,1 A-- 2011- 61)6q CHI DAO BIEN SOAN: Vu Khoa hoc va Da° tao, BO Y t6 CHO BIEN: PGS.TSKH. Le Thanh Phutic NHONG NGUOI BIEN SOAN: PGS.TSKH. Le Thanh Phu& TS. Le Thi Kieu Nhi ThS. Hoang Thi Tuyet Nhung TO CHUC BAN THAO ThS. Phi Van Tham TS. Nguyen Manh Pha © Ban quyin thuOc Bo Y to (Vu Khoa hoc va Dao tao) 9 LoI GIdI THIEU Thtfc hien mot s6 digu cUa Luat Gido duc, BO Gido due & Dao tao va BO Y t6 da ban hanh chtiong trinh khung ciao tao Dudc si Dai hoc. BO Y to to chfic bien soan tai lieu day — hoc cac mon hoc chuyen mon, co ban chuyen nganh theo chuong trinh tren nham Bing budc xay dung bo tai lieu day — hoc chuan v6 chuyen mon de dam bao chat Wong ciao tao nhan luc y tg. Stich "Hod Dai Wong - vo cd Tap 2" duoc hien soan dila tren chuong trinh gido duc dai hoc cUa trtiong Dai hoc Dude Ha NOi, Bo Y to vdi phudng cham: kign thitc co ban, he th6ng; not dung chinh xdc, khoa hoc, cap nhat cac tign bO khoa hoc, ky" thuat hien dai va thiic tin Viet Nam. Stich "Hod Dai Wong - vo co Tap 2" db." duoc bien soan bdi cac nha gido giau kinh nghiem va tam huygt cua truong dai hoc DUoc Ha NOi. Stich "Hod Dai Wong - vo cd Tap 2" da ducic Hoi dOng chuyen mon tham dinh sach va tai lieu day — hoc cila BO Y t6 th'am dinh vao nam 2008. BO Y t6 ban hanh la tai lieu slat chua'n chuyen mon nay dg sti dung cho nganh trong giai doan hien nay. Trong 411a trinh sii dung sach phai duoc chinh 1Y, 136 sung va cap nhat. Bo Y to xin than thanh cam do cac Nha giao, cac chuyen gia caa. trucing Dai hoc Duoc Ha NOi da clanh nhigu ding sic hoan thanh clan sach, cam on GS. Dam Trung Bao va PGS.TS. NO Si Luong da phan bien de cu6n sach sdm hoan thanh kip thai phuc vu cho tong tac dao tao nhan 1iic y tg. Vi Ian dau xuat ban, thong toi mong nhan. &toe y kign dung gop cua dOng nghiep, cac ban sinh vien va cac dOc gia d6 Ian xuat ban sau chtoc hoan thien hon. VU KHOA HOC VA DAO TAO BO Y TE 3 LOI NOI IJAU Hod Dai dicing va Vo co la mon hoc co sei trong chuong trinh dao tao Dtioc si dai hoc. Theo quy dinh cua khung chuong trinh, phdn 1ST thuyet Hod Dai ctiOng va Vo co dtioc giang day i3 hai hoc ky cUa nam ddu cho sinh vien Dtioc he chinh quy. Mon hoc gem 2 hoc phdn: Hoa Dai cuong - Vo co 1 va Hod Dai cticing - Vo co 2. Mei hoc plidn dtioc giang day trong met hoc kY. De dap Ung yeu cat' chung ve nang cao chat Wong dao tao dai hoc va phuong phdp giang day tich cuc, chUng Cal hien soan giao trinh Hoa Dai dicing - Vo co theo htidng tao diet' kien cho sinh vien tii chit nhieu hdn trong hoc tap. Theo do, nhfing kign thtic ciia khoa hod hoc chtoc sap xep, trinh bay met cach hop VT va he thong, vita co ban - hien dai, viia thigt thuc trong van dung, ke ca lien he \Ted kien tit& Sinh - Y - atioc hoc. Muc tieu ciia mon hoc ma sinh vien can phai dat la: 1. Hieu va giai thich duoc cau tao va tinh chat cila cac he vat chat (nguyen tu, nguyen to, phan tU, ph& chat, vat the) nho nhang kign thlic cO ban nhat ye co hoc Wong 2. Xac dinh va ly giai duoc chieu hitting, gidi han cua cac qua trinh hoa hoc nhe van dung cac nguyen ly cita Nhiet deng hoc. 3. Giai thich duoc co the phan tang va cac digu kien can bang hod hoc dUa tren nhang nguyen ly, dinh luat co ban, tit do van dung de giai guy& nhang van de thUc te. 4. Trinh bay duoc mei lien quan glib. au tao va tinh chat dia cac nguyen to va cac hop chat vo co quan trong, theo do hieu va giai thich duoc vai trO cua chung trong Y - Duoc hoc va dec tinh. Giao trinh nay chia lam 2 tap: Tap 1. CAU TAO CHAT VA NHIET DONG HOA HOC gem 6 clutong: Nhfing khai niem va. Dinh luat co ban trong hod hoc/Cau tao nguyen tip va He thong tun hoan cac nguyen te/Lien ket va cau tao phan tit/Phut chat/Cau tao vat the — Phan civic ion/Nhiet deng hoa. hoc. Tap 1 nham gitip sinh vien thvc hien muc tieu 1 va muc tieu 2. 4 Tlap 2. C1-6m 2 phan: Ph'An I. CO CHE PHAN (ING VA CAC TRANG THAI CAN BANG g6m 4 chuong: T6c do va cci the phan iing — Can bang hod hoc/Si hinh thanh va cac tinh chat cila dung dich/Dung dich chat dien ly/Phan 1.tng oxy hod khii va dOng dien. PhAn II. HOA HOC VO CO gem 10 chtiong, trinh bay moi lien quan gifiia cau tao va di-1h chat cac nguyen to va cac hop chat vo co; vai tro va doc tinh cila cluing trong sinh quyen va nhung ling dung trong Y-Dtioc. Tap 2 nham ginp sinh vien thuc hien muc tieu 3 va muc tieu 4. CuOi Tap 1 c6 kern theo cac phu luc de nguai doc tien tra ciiu nhieu hang s6, dai hiong hoac khdi niem thttong clang trong Hod hoc. Trong qua. trinh eu soan, van con. Chung t6i rat mong nhan duoc Sr kien dong k gop va phe binh cUa cac do'ng nghiep, sinh vien va ban doc de lan xuat ban sau tai lieu c6 chat liking cao hon. Ha NIji, Thang 8 nam 2008 Chez bier' PGS.TSKH. LE THANH PHLIOC 5 MUC LUC PHAN I. CO CHE PHAN LING VA CAC TRANG THAI CAN BANG Chtecing 7. TO'c dO va cd chg phan ling. Can bAng hoa hoc 11 Le Thetnh Phu'dc - Le Kie'u Nhi 1. T6c do va co chO phan Ting 12 1.1. Dinh nghia va }Dieu din to-c 4 phan fing 12 1.2. Anh huang dia n6ng 4 den t6c do phan iing 15 1.3. Anh Iniang cua thoi gian den nOng de chat phan ling. PlutOng trinh t6c do tich phan 19 1.4. Anh huang cUa nhiet do den -LOC 4 phan ling 27 1.5. Giai thich cac anh Intang cUa neing 4 va .nhiet di) den to-c do phan ling 29 1.6. Co the phan ling 34 1.7. Chat xtic tic tit& day to-c di) phan iing 38 2. Can bang hod. hoc 42 2.1. Dai Wong 42 2.2. Phuong trinh ding nhiet Van't Hoff. Hang s6 can bang 43 2.3. Hang s6 can bang K va bieu thfic tic dung kho-i Wong Q 47 2.4. Chieu hudng va gidi han cua phan iing 48 2.5. Cac dang cua bieu thlic tic dung khOi luong va hang so- can bang 53 2.6. Giai guy& nhiing van de Binh Wong lien quan den trang thai can bang 55 2.7. Su dich chuyen can bang. Nguyen 1ST Le Chatelier 62 2.8. Can bang trong chuyen hod t6 bao 67 6 Chito'ng 8. Sy' hinh thanh va cac tinh chat ciia dung dich 70 Le Thanh Phu'ac - Hoeing Thi Tuyet Nhung 1. Nhfing van de chung ve ski hinh thanh dung dich 70 1.1. Dinh nghia - Phan loai 70 1.2. Cac cach bigu thi n6ng.d6 • 72 1.3. Can bang pha 77 1.4. DO tan - Nhcing yeu to anh hang den dO tan dia cac chat 91 2. Cac tinh chat dia dung dich chfia chat tan khong din ly va khOng bay hcii 106 2.1. Do ha ap suat hcii cua dung dich. DinhluSt Raoult 1 106 2.2. DO tang nhiOt dO soi dia dung dich. Dinh lust Raoult 2 108 2.3. DO ha nhiOt dO dung dac dia dung dich. Dinh lust Raoult 3 110 2.4. Ap su'at tham than. Dinh it* Van't Hoff 113 3. Tinh chat caa dung dich cac chat din ly 119, Chafing 9. Dung dich chgt dien ly 123 Le Thanh Phu'dc 1. Trang thai cila chat din ly trong dung dich 123 1.1. Dinh nghia - Phan loai chat din ly 123 1.2. DO diOn ly (a) 124 1.3. Hang so diOn ly (K) cua chat din ly yeu. Dinh lust pha loang cua Ostwald 130 1.4. Hoat dO va hO s6 hoat dO 132 2. Thuye't acid — base 140 2.1. Thuye't Arrhenius (thuye't din ly H+, OH-) 140 2.2. Thuyk Bronsted - Lowry (thuyel proton) 141 2.3. Thuye't Lewis (thuy6t electron) 144 3. S4 din ly Thang pH dia. Sorensen 146 3.1. Ski din ly caa. ntioc 146 3.2. Thang pH 147 7 4. Can bang acid — base 150 4.1. Su dien ly cua cac acid yeti 150 4.2. Su dien ly dia cac base yeu 151 4.3. Quan he gifia. Ka va Kb clia mot cap acid - base lien hop 153 4.4. Su dien ly dia acid, base cia chiic. Chat luring tinh 153 4.5. Cach tinh pH mot s6 dung dich 157 5: Dung dich dem. Chat chi thi pH 165 5.1. Dung dich dem 165 5.2. Chat chi thi acid — base 175 6. Can bang trong dung dich dia chat dien ly it tan. Tich so- tan 178 7. Phan ling trong dung dich dien ly 187 Chuang 10. Phan ifng oxy hoa khif va clong dien 191 Le Themh Phu 'dc 1. Phan iing oxy hoa khii. Khai quat ve pin dien h6a 191 1.1. Khai niem chung 191 1.2. So-oxy hoa (S.0) 193 1.3. Can bang phan ling oxy hoa khii 194 1.4. Khai quat ve pin dien hoa 198 2. Pin Galvanic 199 2.1. Cau tao, hoat dOng va so d6 pin Galvanic 199 2.2. Dien the: san pha:m ciia pin Galvanic 202 3. Nang luong tu do Gibbs va cong dien 211 3.1. Dien the pin chuan va hang so- can bang 211 3.2. Anh huang cua n6ng d6 den dien the dia pin. Phtiong trinh Nernst 214 3.3. Dien the cilia pin va moi quan he gifia Q va K 219 3.4. Pin n6ng d6 va do n6ng d6 220 4. Pin Galvanic va van dung thiic t6 223 4.1. Acquy 223 4.2. Su an mon kim loaf: van de moi truang cua dien hoa 226 8 5. Pin dien phan: sit dung nang Wong dien de di6u khie'n phan ling khong tit phat 228 5.1. Nguyen 157 va hoat dOng cUa met pin dien phan 228 5.2. Xdc dinh sari phdm cua phan itng dien phan 229 5.3. Quan he dinh Wong gifia dien tich va san phdm. Dinh ludt Faraday 232 6. Nang Wong trong hoa sinh 234 PHAN II. HOA HOC VO CO Le Thanh Phu'ac Chuo'ng 11. Phan loai va tinh chgt chung cim cac nguyen to 237 1. Phan loai cac nguyen to theo cau hinh electron d trang thdi co ban 237 2. Tinh chat chung cua cac nguyen to nhom chinh (A) 243 3. Tinh chat chung cua cac nguyen t6chuyn tie-p (B) 244 Chuang 12. Hydrogen 255 1. Dac tinh nguyen tit va vat is 255 2. 'Firth chat hod hoc 255 3. Ling dung 257 Chu'o'ng 13. Nguyen to nhom I 258 1. Nhom IA (kim loai ki6m): Li - Na - K - Rb - Cs — Fr 258 2. Nhom IB: Cu - Ag — Au 265 Chuang 14. Nguyen to nhom II 273 1. Nhom IIA (kim loai kim th6): Be - Mg - Ca - Sr - Ba — Ra 273 2. Nhom IIB: Zn - Cd — Hg 280 Chuo'ng 15. Nguyen to nh6m III 289 1. Nhom IIIA: B - Al - Ga - In — Tl 289 2. Nhom IIIB (cac nguyen to d): Sc - Y - La — Ac 297 3. Nhom IIIB (cac nguyen to 0: lanthanid va actinid 299 4. Nhom IIIB: vai tro va itng dung trong Y - Dtioc 299 9 Chu'cing 16. Nguyen to nhom IV 300 1. Nhom IVA: C - Si - Ge - Sn — Pb 300 2. Nhom IVB: Ti - Zr — Hf 322 Chu'cing 17. Nguyen to nhom V 325 1. Nhom VA: N - P - As - Sb - Bi 325 2. Nhom VB: V - Nb - Ta 345 Chu'cing 18. Nguyen to nhom VI 347 1. Nhom VI A: 0 - S - Se - Te - Po 347 2. Nhom VIB: Cr - Mo - W 373 Chu'o'ng 19. Nguyen to nh6m VII 380 1. Nhom VIIA (cac halogen): F - Cl - Br - I — At 380 2. Nhom VIIB: Mn - Tc - Re 395 Chu'cing 20. Nguyen to nhom VIII 400 1. Nhom VIVA (cac khi hi6m): He - Ne - Ar - Kr - Xe - Rn 400 2. Nhom VIIIB: Fe - Co - Ni / Ru - Rh - Pd / Os - Ir — Pt 403 Teti lieu tharn kheto 421 10 PHAN I CO CHE PHAN AG VA CAC TRANG THAI CAN BANG Chtfdng 7 ToC DO VA CO CHE PHAN (MG. CAN BANG HOA HOC M V C TJ U 1. Trinh bay each xac dinh cac thanh phan trong phuting trinh to'c dd. 2. Viet phodng trinh tdc otc5 vi phan vet tich phdn cho cac phcin Ong bdc 0, 1, 2, va gidi etude mot selbai town tie thu'c te: 3. Gidi thich cinh hu'dng awl nang dd, nhiet dd va yeit to khong gian can toe phdn Ong. 4. Trinh bay 2 ddc diem caa chat xac teic vet nhieng diem cktc Net czia xi c bac enzym. 5. Xac dinh duvc ch,ieu hu'dng va gidi han cda mot phdn zing qua cac gici tri cda Q, K vet dG. Gidi quyet etude mot so-be:a town dat ra tic thOc te: 6. Trinh bay nguyenlY Le Chatelier va each van dung trong chuyen dick can bang. Phan -tang hod hoc la nhiing qua trinh dOng hoc, trong do vat chat va nang Wong lien tuc hien dOi. Bleu dien cac phan iing &lair clang phtiong trinh hod hoc la rat thuan tien va la tong cu de tinh toan Wong san phdm tao thanh tii m0 Wong chat ban dau (chat phan ling) da biet. Tuy nhien, phtiong trinh hod hoc khong cho to biet ba thong tin quan trong cUa mot phan ling hod hoc: Tai thai diem bat dau, phan iing co kha nang xay ra tai phat hay khong? No giai phong nang Wong hay can cung cap nang Wong? Tai mot thai diem, phan iing xay ra nhanh hay cham? Theo co the nil-Li the nao? NOng dO cac chat dau va san phdm la bao nhieu khi phan -tang ket dale? Be nhdn biet thong tin dau, Nhiet &Ong hod hoc (chtiOng 6) chi ra rang, mot phan ling bat kY chi có the xay ra tai phat khi AGp„ < 0. 11 Nhung not dung cila chtiong nay se cho phep xac dinh hai thong tin tiep theo. 1. ToC DO VA CO CHg PHAN fiNG 1.1. Dinh nghia va bieu din Vic do phan ling • Tdc dO phdn zing la sti bien doi niing do cua chat dciu hay san phei'm trong mot don vi thdi gian: + C2-CI + AC t 2- t1 — At (7-1) day, V IA tec dO trung binh trong khoang thai gian tit t1den t2; AC IA su bien doi n6ng dO mol/L cna chat dau hay san phAm tit C1den C2; vi tO-c dO IA dai lacing khong có gia tri am, nen dau + itng v6i viec xac dinh t6c do theo sit Eden d6i n6ng do san phAm, con dau - itng voi chat dau. Khi At —> 0, phtiong trinh (7-1) cho t6c dO titc thai: V = +dc dt Doi voi mot phan ling bat kST, chang han: aA + bB —> eE + fF (7-2) trong do a, b, e, f IA cac he s6 tST Wong trong phuong trinh hoa hoc, thi tec dO phan ling dttoc xac dinh bang he thfic: V dc A dC B dc E dc F (7-3) adt bdt edt fdt Chu 51: Don vi thai gian trong do tee dO phan ling do the IA giay (s), phut (min), gia (h), ngay (d) hoac thong, nAm. Theo do, t6c dO co this nguyen IA mol/Lgiay (hoac mol.L-1.s4); mol/Lphnt (hoac Gia tri cua V phu thuOc vao viec quy ve chat nao (trong pinking trinh hod hoc) de tinh: chat có he s6 ty Wong Ion, gia tri bang s6 cila V cang 16n. • Vi du ve' ccich xac dinh tdc de): phcin zing theo thai gian. Xet phdn zing thuCin nghich d pha khi gia'a ethylen va ozon (kw khoi quang hoci, gay o nhijm tit giao thong a thanh pho): C2H4(k) + 03(k) C2H4O (k) + 02(k) Tit he s6 tY' Wong cho thay n6ng do caa hai chat dau giam xueing voi t6c dO nhu nhau: 12 V = A[C2H 4 ] A[03 ] At At Bang cach theo doi nemg d6 dia mot trong hai chat dau, to c6 the tinh dtfOc t6c d6 phan itng. Gia sit da bi'et ang d6 03trong melt binh kin 6 30°C (303K) tai cac thai diem khac nhau trong phut dau tien sau khi C2H4dtioc dtta vao binh (bang 7.1). Bang 7.1. N6ng d6 036 cac thOi diem khac nhau trong phgn Ong vdi C2H46 303K Thesi gian (s) N6ng d6 03(mol/L) 0,0 3,20.10-5 10,0 2,42.105 20,0 1,95.10-5 30,0 1,63.10" 40,0 1,40.10' 50,0 1,23.10-5 60,0 1,10.10' + Tinh to/c d6 trung binh cua phan iing trong 60s: V60 = (1,10.10-5mol/L) -(3,2.10-5mol/L) = 3,50.10-7 mol/L.s 60,0 s - 0,0 s + Tinh t6c d6 trung binh cUa phan ung trong 10s dau tien: (2,42.10-5mol/L) - (3,20.10-5mol/L) VIO(t16u) - 7,8.10-7mol/L.s 10,0s-0,0s + Tinh t6c do trung binh cua phan itng trong lOs cu6i cila phut dau tien: v.10(cum= (1,10.10-5mol/L) - (1,23.10-5mol/L) = 1,3.10-7mol/L.s 60,0 s -50,0 s Tit cac ke't qua tinh tren day cho thay: ban than t6c d8 phan ling luon bi:en doi theo thai gian; t6c do chain dan trong qua trinh phan fing (t6c di) lOs dau nhanh .gap 6 tan lOs cu6i); t6c d6 trung binh trong mot khoang thai gian khong cho bie't t6c do tai mot thai diem. Neu chon khoang thai gian cang ngan, gia tri t6c d6 thu duoc cang gan t6c d6 tiic thai. + Sit 'Dien doi t6c di) phan itng ciing c6 the th'ay dttoc bang cach ye d6 thi n8ng d6 theo thai gian (hinh 7.1). D6 d6c (he s6 g6c = tga) cua &fang thang (Ay/Ax, 6 vi du dang xet tic la A[03]/At) not hai diem bat kS7 cho bie't t6c do trung binh trong khoang thai gian d6. D6 eldc czia tie-p tuyen 13 udi du'eing cong tai mot thdi diem cu the' cho bi'dt tdc dO tic thol tai thOi diem do. Vi du tren hinh 7.1, to/c dO phan -ling 6 giay this 35 sau khi phan Ung bait dau la 2,50.10' mol/L.s, do la dO d6c cUa tiep tuyen \Ted duang cong tai thai diem t = 35s. 4j0J N6ng dO 03(mol/L x 105) flung V (mol/L.$) 3,0 2.0 1,0 a 10,0 x 10-7 b 3,50 x 10-7 7,80 x 10-7 d 2,50 x 10-7 e 1,30 x 10-7 1 60 10 50 2(1 3(1 40 Thai gian (s) Hinh 7.1. Do thi Wong c16 03theo thai gian trong phan ling vOi C2H4(ye theo so lieu cOa bang 7.1 va cac ket qua tinh tOc do cho vi du clang xet). DO dific cOa duting thang b la to'c dO trung binh di' a phan ling ci cä 60s, cOa duttng thAng c va e le tek do trung binh 6 lOs dgu va 10s cu6i; con dO dek cOa a la t6c c10 ban au tai thai diem t = 0,0s, cOa d la tcic chi .ttic thai tai thOi diem t = 35s • Nhi:ing hiu y can dung cho phAn trinh bay tiep sau: Thuat ngia "t6c dO phan ling" thong thttang la de chi t6c dO tfic thai. T6c dO ban dau la t6c dO tic thai tai thai diem cac chat dau moi trOn fan vdi nhau (nghia la 6 t = 0). Khi do, n6ng dO san pham la rat nhO nen teic do phan ling nghich khong clang ke. Trii nhiing truang hop dac biet, to se sit dung t6c dO ban dau de xac Binh cac thong s6 Ong hoc khac cua phan T6c dO phan itng phu thuOc trtioc het vao ban chat ciia cac chat tham gia phan itng, this den la n6ng do, trang thai vat ly cua chung, nhiet do ma tai do phan itng xay ra va tac dung cila chat xlic tac. 14 1.2. Anh htaing clad nang do clgn tac do phan iing • Phticing trinh to-c di) hay dinh luty tij-c d() (con goi la dinh ludt tac dung khai Wong, do Cato Guldberg va Peter Waage, hai nha hod hoc Na Uy, dua ra dang thiic ban ddu nam 1864): • Tdc dO phdn zing 0 le thuein voi, tich so nesing dO (vdi so ma thich hop) cda cac chlit tham gia phdn zing. vdi mat phan iing chung, chang han: aA + bB —> san phdm Phuong trinh tac do c6 V = k.[A]m.[B]" (7-4) [A], [B] - n6ng do mol/L cua chdt A va B 6 thOi digm tinh V. m, n - nhUng con so/duct xac dinh bang thiic nghi0m; tang m + n &toe goi la bac cua phdn zing, trong do m la bek rieng ctdi vdi A va n la bac rieng ctoi vdi B. Cac s6 mu khong nhdt thigt phai c6 bdt ky mai quan 110 nab vdi cac 110 s6 a, b trong phtiong trinh phan k - he so q, 10, goi la hang so-tot do, chi phu thuac vao ban chdt cUa chd.t phan iing va nhigt do. voi mat phan -tang xac dinh va 6 nhigt ct6 khong doi thi k = const. Khi n6ng d6 cac chdt phan iing dgu bang 1 mol/L, k = V va goi là tdc dO rieng cda phdn Phuong trinh (7-4) cluoc goi la dinh ludt tac do, phuong trinh tac do hay pinking trinh clang hoc hinh thiic cua phan ling; no là phuong trinh co ban cUa dang hod hoc va &foe xac dinh bang thiic nghi.0m. • tim chtoc cac thanh phdn cua dinh ludt tot do (g6m tac do, bdc phan ling va hang so/tac do), ngtiOi ta phai thiic hiOn nhigu thi nghi0m 6 cac n6ng do ban cldu khac nhau de xac dinh mat boat gia tri van tac ban ddu. Mat khi cla" bigt phuong trinh tac clod nhik do nao d6, ta c6 thg dung no de xac dinh tac do 6 bdt ky n6ng do chdt ban cidu nao. Chu 51: DOi,v6iphan ling clang thg, la. phan gicia cac chdt 6 trong tong 1 pha (chang han phan iing giita cac chdt khi, giita cac chdt hoa tan trong dung dich), n6ng do cac chdt phan *rig (Moe th0 hi0n ddy du trong pinking trinh tac do. • v6i phan ling di thg, la phan Ung gicia cac chdt khac pha (chang han phan iing gifia chdt khi va chdt ran hay giita chdt hoa tan va chdt ran), thi trong pinking trinh tot do khong c6 mat n.6ng dQ chdt ran, vi no du oc xem la c6 gia tri kh6ng doi va duoc dua vac) hang so-tac do. VI du: 15 S (r) + 02(k) -> SO2(k) V = k'.const.[02] = k.[02], • Xac dinh bac phan ling a/ Bac chung ciia phan ling, hay bac rieng doi vdi ding chat, thltang la s6 nguyen &tong hay 0, nhttng cling c6 the la phan s6 hoac am. Dieu nay ctuOc thay o cac vi du sau. - Phan ling: NO (k) + 03(k) ---> NO2(k) + 0, (k) Phuong trinh to/c do (da duoc xac dinh qua thtic nghi:On) IA: V = k.[N0].[03] . Vay, phan ling nay la bac 1 dal voi. NO (t6c do phan iing phu thuac n8ng do NO tang theo bac 1 [NO]'). N6 cling la bac 1 doi voli. 03, la [03] 1. Tang cac bac rieng se la bac cila toan bo phan ling. Vay phan ling nay la bac 2. - Phan ling: 2NO2(k) + F2(k) -> 2NO2F (k) Pinking trinh t6c do duoc xac dinh: V k.[NO2].[F2] Vay, phan ling la bac 1 doi vdi NO2, bac 1 dal vdi F2va toan ba phan ling la bac 2. Phan fing gifia 2 chat long: (CH3)3CBr (1) + H2O (1) --> (CH3)3COH (1) + HBr (aq) Phtiong trinh t6c do: V = k.[(CH3)3CBr] Phan ling la bac 1 d6i v6i. 2-bromo-2-methylpropan. Pang chn Sr la riling do rat6c khong xuat hien trong phuong trinh toc do. Phan ling la bac 0 doi vdi Hz0 ([H90]°). Di6u nay co nghia la t6c do phan ling khong phu thuac vao ang do H2O (vi no la dung moi neing do 16n c6 the xem la khong d6i). Ta cling c6 the viet pinking trinh t6c do: V = k.[(CH3)3CBr].[H20]°, va bac clia toan ba phan ling la bac 1. - Phan fing phan huS, 1. chat khi: CH3CHO (k) -> CH4(k) + CO (k) Phuong trinh Vic do: V = k.[CH3CH0r2 Phan ling c6 bac 3/2 dal voi. CH3CHO, bac phan ling chung cling la bac 3/2. 16 - Phan Ung phan huY' khi ozon: 2 03(k) Phuong trinh t6c d6: 3 02(k) V = k.[03]2.[02] 1= k.[03]21[02] Vay, n'eu n6ng d6 02tang len gap doi thi t6c d6 phan giam xu6ng mot niia. Bac cua phan chung la bac 1. b/ De xac dinh bac phan itng, nguai ta tie'n hanh nhieu thi nghiem. M6i thi nghiem bat dau 6 ang d6 khac nhau d6i vdi chat khao sat, trong khi nOng d6 cac chat khac &Joe git nguyen. Tii m6i thi nghiem se tim thay mot to-c d6 ban dau. So sanh cac gia tri t6c d6, ta tim dude bac phan Vi du: De xac dinh bac ciia. phan NO2(k) + CO (k) —> NO (k) + CO2(k) mau nau khong mau khong mau khong mau nguai ta tien hanh cac thi nghiem do mau trong binh mau (da bie-t the tich) dm may quang phO. Vi chi NO2có mau (do hap thu anh sang nhin thay trong mot khoang bulk song hep) nen t6c d6 giam ang d6 dia no duck do mau theo thcii gian. Cac du lieu thuc nghiem thu &foe ghi trong bang 7.2. Bang 7.2. Cac t6c d6 ban dau va n6ng d6 ban dgu trong 3 thi nghiOm cOa phgn Ong gii7a NO2va CO 6 25°C Thi nghiem T6c do ban au (mol/L.$) [NO2] ban crau (mol/L) [CO] ban dau (mol/L) 1 0,0050 0,10 0,10 2 0,0800 0,40 0,10 3 0,0050 0,10 0,20 Pinking trinh t6c d6 cho phan tang dang khao sat &toe viet &ten clang tong quat la: V = k.[NO2] m.[CO]" De xac dinh m va n, ta lap ty s6 gii a cac plitiong trinh t6c d6 d cac thi nghiem, chn y gian uOc k (do 6 ding nhiet d6, gia tri cila no khong doi.) va gian cac nong d6 giong nhau: V2= k. [NO2]2n. [CO]2 k.[NO2 r r 7■TC) 12 \m J [Na]i 0,0800 mol/L.s (0,40 mol/L m 0,0050 mol/L.s 0,10 mol/L TAN TAO UNIVERSITY LIBRARY 17 (chn nhang con s6 ghi phia duoi V va [ ] la s6 this tti dm till nghi:e.m). Tif do tim thay m = 2, phan -ling la bac 2 deci vdi NO2. V3=, k.[NO2 ]i.[C0]`31_ ([C0]3 V1 k.[1\102 ] .[C0]11 [C0]1 0,0050 mol/L.s (0,20 mol/L)n 0,0050 mol/L.s 0,10 mol/L Tit do tim thay n = 0, phan Ting la bac 0 cloi vdi CO. Phuong trinh toc do cua phan Ting duoc xac dinh qua thuc nghi'm la: V = k.[NO2]2.[C0]° = k.[NO2]2 Vay phan ling chung clang xet la phan -ling bac 2. • Xac dinh hAng so t6c do Khi da bie't cac gia tri t6c do tai mot nhiet c16, ang c16 chat phan ling va bac phan ta de dang tim duoc gia tri cila hang s6 t6c do k. D4 vi du, ta tra lai phan ling gilla NO2 va CO vita xet tren, thi gia tri k co the chide tim thay, chung han tit thi nghi.01 3, bang each lap he thfic sau: k= V3 0,0050 mol/L.s = 0,50 L.mol-1 .s-1 [NO2 ]i (0,10 mol/L)2 Di nhien d ca 3 lan thi nghi4m (tai 25°C), k cua phan -ling clang xet phai có cimg gia tri (frit nhung sai s6 th-qc nghi.rn cho phep ttiOng -ling vdi do chinh xac cua phuong phap do cluoc sU dung). Bang each b6 tri thi nghi:On va cach tinh tttdng tit nhtt vay, chting ta có the tim cluoc gia tri k cho moi phan ling có cac bac khac nhau. Chti ST rang, this nguyen (don vi) cila hang s6 t6c di) phu thu(ic vao bac cua phan ling (bang 7.3). Bang 7.3. Cac don vi coa .hang s6 to‘c do k cho cac bac phan khac nhau Bac phin ang Don vi cita k (thoi gian t theo gray = s) 0 mol/L.s (hoac mol.L-1.s-1 ) 1 1/s (hoac s-1 ) 2 L/mol.s (hoac L.mo1-1.s-1) 3 C/mo12.s (h0c L2.mo1-2.s-1) 18 / Cong thfic chung cho n6ng dQ mol.L-1: don vi k rno/r4c-I — t hoac cho ang dQ khdi quat: don vi cila k = (don vi do ang 4)1-B4c x (don vi do thai gian)-1 1.3. Anh Inking cita- thdi gian den niing d'(;) chat phan itng. Phtidng trinh to-c do tich phan Cdc phtiong trinh t6c do viia xet tren day chata bao g6m thai gian dttoi Bang Wen thien. Chung chi cho ta biet t6c d0 hay n6ng 4 tai mot thai diem. tra lai cdc cau hOi: sau bao lau thi mot chat phan ling het, hoac nan.g dQ cua no- bang may sau mot khoang thai gian nao do, ngtiai ta Can phai xay thing cdc pinking trinh mo to moi quan he dinh Wong gifia n8ng d6 va thai gian cho cac phan -tang a cdc bac khac nhau. Nhcing phtiong trinh nhu vay dUoc goi la cdc phtiong trinh dOng hoc hay phu'ang trinh tde ctO tich phan cua cdc phan iing hod hoc. Chung do'ng thai la cong cu ginp cho viec tha'm dinh va xdc dinh cdc thong s6 diing hoc khdc (bac phan ling, hang s6 t6c do, chu kST ban huY...). 1/ Phdn ang bdc khong la phan fing ma t6c di) cila no la mot hang s6, khong phu thuQc vao n6ng do cua cdc chat phan ling va thai gian. Cdc phan ling A —> san pharn la bac khong thi pinking trinh t6c dQ vi phan cho chat phan -Cing A nhtt sau: - d[A] V = = ko d[A] = - ko.dt (7-5) dt Lay tich phan phtiong trinh tren trong khoang tii n6ng d6 ban d'au [No 6 t = 0 den nang dQ [A] 3 thai di6'm t, thu dtioc pinking trinh t6c 4 tich phan: [A] fd[A] = - kofdt [A] - [A]0= - ko t [A]„ [A] = [A])- kot (7-6) Thai gian ban hug, hay chu k5' ban hug, ky hie:u t112, là thai gian can thiet cue' mot idea chat ban ctdu bien thanh sdn phcim. [A]o poi vdi phan ling bac khong, ti/2 (7-7) 2k0 Khi phtiong trinh duang thang (7-6) duoc bieu din tren do thi nang do - thai gian thi he so-goc cua &tang thang tga = -k0 (7-8) 19 [A], DO d6c = -k„ Hirai 7.2. D6 UV phtiong trinh t6c dO tich phan cad phdn sing bdc khOng - Vi du: 'roc dO phai mau cua mot ch6 pham giau nhorn phosphat (dtioc do qua sti giam dO hap thu quang A tai = 500nm) tuan theo t6c dO bac khong voi k0= 0,00082 dO hap thu/gia d 60°C. Vay, sau bao lau mau cua the pham phai di mot niia, neu mau hien tai cita no do thicic la A0= 0,470 dO hap thu. Gidi Xem A0= [A]ova van dung pinking trinh (7-7), thu &toe: A„ = 0,470 dO hap thu t1/2 = 2k 0 2 x (8,2.10-4dO hap thn/giii) = 2,9.102gia 12 ngay) 21 Phdn ang btic 1: Cac phan ling A ----> sail phalli la bac 1 thi pluicing trinh to'c dO vi phan có dang: - d[A] V k[A] dt = d[A] k.dt (7-9) [Al = - suy ra phthing trinh to-c dO tich In ['Al° = kt [A] va cac pinking trinh he qua: 1n[A] = ln[A]0- kt hoac phan: hoac lg[A] ig[A]o kt [A] 2,303 lg[A]0 kt = 2,303 (7-10) (7-11) 1 t = In [A]0 2,303 lg [A]0 ho4c t = (7-12) k [A] k [A] Bdi 1 dinh nghia [A] = 2 — [A]0d t = t112 , nen: 20 t1/2 = I —In [A] I 0= 1n2 = 0,693 k 1 k k [At) (7-13) a day can lu'u - Chu kST ban huSi cila chat a phan fing bac 1 (tai nhiet do nhat dinh) là mot hang s6khong phu thuOc vao n6ng d6 ban Tau. - Neu bi4u thi plation.g trinh (7-11) theo y = ln[A] va x = t: 1n[A] = -kt In[A]o y = mx + b to thu dti6c pinking trinh &tang thang ma he so goc (dO d6c) cila no bang m = -k = tga va eat true y tai b = ln[A]ot = 0 (hinh 7.3). Neil ye .d6 thi ln[chat phan ling] theo, thai gian ma thu &toe mot duang thang di xu6ng thi do la clang phan ling bac 1 doi v6i chat phan deing thii tim du6c hang so t6c ln[A] do k nh6 xac dinh dO d6c. C6n ne/u ye d6 thi [chat phan ling] theo thai. gian ma thu dtf6c mot du6ng thang di xu6ng thi do la phan Ung bac khong doi vdi chat phan iing, d6ng I [Al, DO clCic = -k t thoi tim du 6c k0qua dO d6c cua duang thang. Hinh 7.3. D6 thi phttong trinh to.c do tich phan b0c 1 Ngu chat phan ling 6 the khi thi trong cac phucing trinh t6c do tich phan co th4 thay the n6ng dO mol/L bang n'Ong dO phan mol (N) hoac bang dp suat (P), vi chting la nhiing dai luring q, le vOi nhau. Chang han pinking trinh (7-10) khi ay có = kt hoac In = kt (7-14) - Phan Ung bac 1 thu6ng gap la nhang phan Ung phan huST chgt khi hay chat 16ng, phan 1 ng thuS, phan, phan 1 ng phan ra phong xa... nhu mot s6 vi du sau. + Vi du 1: 2N2 05(k) ---> 2N204(k) + 02(k) co phudng trinh t6c do &toe xac dinh: V = k.[N2 05], vdi k = 0,0168 s 16 40°C. Tinh s6 mol N2 05con lai sau 1 philt phan iing, ngu ban dau có 2,5mol N205chila trong binh th4 tich 5L va nhiet dO dude duy tri c3 40°C. 21 Gidi Pinking trinh t6c d6 va thin vi cUa k cho thgy day la phan tang bac 1. 2,5 mol N6ng d6 ban dau cUa N205là: [N,05}0= 5 L = 0,500 M Van dung phuong trinh (7-11): ln[N2 05] = ln[N201 - kt = in 0,500 - 0,0168 s-1x 60 s = -1,701 • = [N205] = 0,182 M S6 mol N2 05con lai trong binh 5L sau 1 phut la: 5 x0,182 mol = 0,910 mol L + Vi du 2: Su phan huY hydrogen peroxyd: 2H202(1) ---> 2H2 0 (1) + 02(k) duoc xac dinh la phan ling bac 1. Trong 1 thi nghi6m c6 xac tac d nhi6t d6 phOng, nguai to theo doi ski phan huY' H202bang cach do th6 tich 02giai phong nh6 mot buret khi va nhan thy sau 65 phut niing 0 H202(bi6u thi bang s6 th6 tich 02khi cho mot th6 tich H2 02 16n.g. O buret doc don vi th4 tich theo mL) là 9,6, con khi rndi bat d'Au do là 57,90. a) Tinh hang s6 t6c dO k. b) Tim thai gian ban huST t1;2. c) Sau 15 phUt, neing d6 H202la bao nhieu. Gidi a) Van dung piniong trinh (7-10) hovO.c (7-12), thu duoc: k = 2,3031g (H202)0 = 2,3031g57'90 = 0,0277 phut t (H202 ) 65 9,60 b) Van dung phudng trinh (7-13), dtioc: 0,693 0,693 t I 2 = = 25 phut 0,0277 philt-1 c) N6ng d6 H2 02con lai sau 15 philt: 2,3031g 57,90 0,0277 = (H202 ) = 38,22 15 (H2 02 ) (O day can hi6u, tai th6i diem nay, 1 the tich H2 02lOng con co th6 giai phong 38,22 th6 tich 02khi). 22 + Vi du 3: Carbon 14 phan ra phong xa p (beta) theo phan 14/1/4T e ((3-) 6 7' có chu kST ban ra la 5730 nam. Tinh tu6i cua mot m'Au go khao c6 có do phong xa bang 71% d6 phong xa cua mdu g6 hien tai? Gicii Dtia cac dfi lieu \Tao phuong trinh (7-13) va (7-12), thu duoc: 0,693 5730 nam = k = 1,21.10-4nam-1 k 2,303 100 t = lg = 2831 nam 1,21.10-4nam-1 71 + Vi du 4: M6t ddn thu6c chlia aspirin (= Asp) clang lOng Can &lac pha chg cho digu tri Odin dau, ha sift va thong ke't tap ti.4u cdu. N6 chila 325mg (Asp)/5 mL hay 6,5g (Asp)/100 mL. DO tan ciia Asp a 25°C la 0,33g/100 mL. Mid vay dang thu6c la hon dich (tieu phan chat tan dtioi dang cac hat treo 10 lung va gidi phong ddn Asp vao dung dich). Biel hang s6 t6c do phan 1n6'7 Asp trong dung dich la bac 1 va bang s-I. a) Tinh k(, cUa t6c do phan huy boat chS.t (Asp) trong hon dich. b) Tinh thai han sif dung ciia hon dich pha che, nghia la khi van con 90% Asp chua bi phan huST. Gidi a) Phan hq Asp trong dung dich la phan ling bac 1 nen theo pinking trinh (7-9), to c6: — d[Asp] = k.[Asp] dt ,Vi [Asp] la khong d6i va bang do tan cUa Asp chling nao hem dich con On tai. 0 thai gian nay to/c do phan huY)Asp la bac khong bieu kien (khi h6n dich tan het no se tr6 ve Sc 1), nen: — d[Asp] k.[Asp] = ko dt k,, = (4,5.10-6s 1 ) x (0,33g/100 mL) = 1,5.10 6 gs-1 100mL b) Thai gian thu6c van con 90% chua bi phan huy duoc tinh theo phudng - trinh (7-6): 23 t = 0,10 [Aspjo= (0,10)(6,5g/100 mL), = 4,3.105s = 5 ngay k0 1,5.10-6g/100 3/ Phdn zing bac 2 Phan Ting A + B —> san pha'm la bac 2 thi plationg trinh to-c do vi phan có dang: - d[A] - [B] V = d d = k[A][B] (7-15) t dt Goi a va b la n6ng dQ ban dau cilia A va B, va x la n8ng dQ da phan ling den thai di4m t, thi: V = —dx = k(a - x)(b - x) (7-16) dt Lay tich phan pinking trinh tren, thu duQc phuong trinh t6c do tich phan: 1 ln b (a — x) kt (7-17) (a — b) a (b - x) Khi A va B có cimg n6ng dQ (a = b), hoac coi phan ling la ciia cang 1 chat 2A —> san pham, thi: V d x 2 k = = (a - x) dt (7-18) Phuong trinh teCc 1 ( x do tich phan cila (7-18) la: 1 1 = kt (7-19) = kt hoac [A] [A]0 va chu ky ban h4 cUa phan ling bac 2 suy ra tit 1 (7-19) la: (7-20) t 1 / 2 = ak D6 thi bi4u din phuong trinh (7-19) tticing ling vdi 1 1 = kt + [A] [A]c, y = mx + b la mot duang thang có dQ d6c m = k = tga. Vay, khi ye do thi 1/[chat phan ling] theo thai gian ma thu chicle mot &fang tha'ng, thi do la phan ling bac 2 (hinh 7.4). 24 Chit 1 + Khac Voi phan Ting bac 1, thai [A] gian ban huY' cUa phan ling bac 2 phu thuQc vao ang dQ ban dau dia chat phan Dieu do cho thay, thai gian niia phan Ung se ngan hdn khi có nhieu mol chat có mat de va cham va phan nhau. MQt ming dQ ban dau cao se có mot thai gian ban huy ngan, trong khi mot nong Do d6c = k 1 [A]0 t do ban dau thap se c6 mot thai gian ban h4 dai hdn. Hinh 7.4. DO thi phuting trinh tek dO tich phan b0c 2 + Vi du: Phan ling xa phOng hoa ethyl acetat 6 25°C la: CH3C00C21-1, + NaOH ---> CH3COONa + C2H5OH Neng dQ ban dau cua CH3C00C2H5va NaOH deu bang 0,01500 M. Sau 20 phut ang dQ kiem giam mat 0,00993 M. Tinh: a) Hang so-t6c b) Thai gian ban huST cUa phan Cho biet phuong trinh t6c dQ V = k.[CH3C00C2H5].[Na0H]. Gidi Phliong trinh t6c di) chi ra do la phan ling bac 2. a) No'ng dQ ban dau cila 2 chat phan Ung bang nhau nen có the van dung phuong trinh (7-19) de xac dinh: 1 0,00993 k = = 6,531-1-nor' .phtit-1 0,015 x 20 (0,01500 - 0,00993) b) Va van dung phuon.g trinh (7-20) de tim: t1/2 = 1 = 10,21 phtit 0,015 x 6,53 Lu'u gia sii trong phan iing tren ma ban dau cho [NaOH] >> [CH3C00C2H5], thl sau mot thai gian [CH3C00C2H5] thay d6i dang ke so vai ang dQ ban dau, trong khi [NaOH] thay d6i khang clang ke so voi ang di) ban dau cila no (coi nhu khang d6i). Khi do phuong trinh t6c dQ duos viet: V = kl.[CH3C00C2H5], trong do k' = k. [NaOH] va pinking trinh duoc coi la bac 1 gia. 25 41 Phdn zing b(tc 3: Phan iing bac 3 tong quat có dang A + B + C --> san pham. Goi a, b va c la n6ng do ban dau cila A, B va C, va x la n6ng do da phan ling cua chting sau thai gian t, to có phtiong trinh t6c dO vi phan: V = dx k(a - x)(b - x)(c - x) (7-21) dt - Trong trurang hop a = b = c hoac phan ling bac 3 la cila 1 chat, chang han 3A --> sari pham, thi: dx V = dt k(a - x)3 (7-22) Phan ly bie-n s6 va lay tich phan, thu dive phuing trinh t6c do tich phan la: 1 1 = 2kt (7-23) (a - x)2 a' 'Cif do suy ra chu kST ban hug: 3 t(/- 2a 21: 51 Phdn zing beic n: Dang phan ling là: A+B+C+...+K san phAm n (phan tir (7-24) (7-25) De don gian, gia sii n6ng do ban dau cita cac chat bang nhau va bang a, va x la n6ng dO da phan Ting cua thong, thi cac phaang trinh t6c do vi phan va tich phan thu dive nhti sau: dx = kn (a - x)" (7-26) dt (n —1) — ) Tit do suy ra chu kST ban hug: 1 2n-1- t 1/2(n) (n-1) k n a n-1 = kri t (7-27) (7-28) CS day, k„ va t1,2(„) la hang s6 to-c do bac n va chu kS7 ban hug cila phan -tang bac n, vdi n 1. 26 1.4. Anh htiang cita nhit coo d6n toe do phan ling Nhiet dO anh hoeing den t6c dO cua da so cac phan ling bang each gia tang hang s6 Vic dO k. Kinh nghiem cho thay, t6c dO phan iing thtiong tang 2-4 Lan m61 khi tang nhiet dO len 10K (hay 10°C). Con so-cho biet so Mn tang ciia tO'c phdn zing khi nhiet ctO tang them 10 c:1-0 goi là he so nhiet ciict tele ctO phcin zing va ky hieu la y. Theo do, mot phan ling 6 ding cac di6u kien khac thi: -= VT + 10 VT k T 10 k T (7-29) N6u 6 nhiet dO T, van tic cua phan ling la V, thi 6 nhiet do T2van tic V2 cna phan ling chicle tinh theo biL thi c kinh nghiem dia Van't Hoff: - Vz =Y 1 " .V/ (7-30) Vay, nhiet dO lam tang tic dO phan ling, ma thtic chat la lam tang hang so -LOC dO k theo mot ham Bieu thlic (7-30) chi gain thing trong khoang nhiet dO khong cao. + Vi du: MOt phan ling coy = 2 dtioc hoan thanh sau 2 ngay 6 0°C. Vay cling phan ling do, ne-u tie'n hanh 6 100°C thi: a) Tic dO phan ling se tang bao nhieu lain. b) No dtiic hoan thanh trong bao nhieu Gicii a) Van dung bieu.thfic (7-30), to có: loo V100= 2 lo = 2)0 Vo Tic do phan ling tang 210lain. b) Vi tic dO phan ling ty le nghich vdi thai gian hoan thanh t, nen: V100 Vo t o t too 2") 1100 (2 x 24 x 60) phut 3 pinit 2'0 d 100°C phan ling hoan thanh chi sau khoang 3 phut. - Phu'dng trinh Arrhenius: Tii nhung ke't qua nghien cflu chinh xac, nam 1889 nha hod hoc Thuy Dien Svante Arrhenius da tim ra mo'i quan he theo ham mu am gifia nhiet do va hang s6 tic dO. Cj clang hien dai, phlicing trinh Arrhenius dtioc 27 k= A. e-Ea/RT 6 day, k - hang s6 t6c d6. T - nhi6t d6 tuy6t de:a. R - hang s6 khi. e - co sec logarit tv nhien. (7-31) A - mot hang s6 có lien quan den s4 dinh litiong trong st.i va cham giiia cac phan tii (Sr nghia dia. no &toe thao luan a phia sau). E. - na ng lu'o'ng hoat hod cad phan zing, theo Arrhenius, la ruing lacing toi thdu ma cac phcin tec' can phdi c6 cte' phan zing Cy nghia chinh xac hdn dm no, cang nhu A, se not tiep a phan sau). Khi lay R = 8,314 J/K.mol thi Eacó thin vi la J/mol. Nilo rang, khi nhi6t d6 tang, so-mu am se nha hdn, gia tri k ft-6 len lon hdn, nghia la t6c dO tang. Cluing ta có tinh ctiOc E. bang cach lay In hai v6 phtiOng trinh Arrhenius va chuyen thanh dang phtiong trinh mot &tang thing: Ink Y = ( Ea 1 R T i = mx + b + InA (7-32) D6 thi Ink theo 1/T cho mot &tang thing ma d6 d6c dm no la - E./R va cat y d lnA (hinh 7.5). Bang thifc nghi6m, do mot s6 gia tri k a cac nhi6t d6 khac nhau va lap d6 thi nhii hinh 7.5, vi R da biet, nen tinh &toe Ea= -R.tga. Cling có the xac dinh E. bang cach lay dao ham Ink theo T: cl In k Ea ( dT RT 2 7-33) Neu xem E. = const, tich phan phitong trinh tren tilt T1den T2, thu &foe: Ink I/T (K- ') Hinh 7.5. Xac dinh Eab6ng do thi bie'u din Ink theo 1/T k = _Ea r1 1 Ea k l R \ T2 T1) R ( 1 1 T1 T2 (7-34) Thilc to rat don gian, chi can xac dinh k1, k2cua phan ling c3 hai nhiet d6 T1, T2r6i thay vao (7-34) ta se tim diloc gia tri Ea. Ngiicic lai, n6u da biet EaIra hang s6 t6c dO tai mot nhiet d6 nao do, ta c6 the tinh dtioc hang s6 t6c c/6 a cac nhi6t do khac. 28 + Vi du: Tinh Eacua phan ling phan 2H1 (k) —> H2(k) 12(k) Biet k 6 500K la 9,51.10:9L/mol.s va 6 600K la 1,10.10 ' L/mol.s. Giai Ap dung phtiong trinh (7-34), to ( k Ea -R In 2-- k I \ T 1 2 T1 ( 1,10.10-5Lb-11°1.s \( 1 1 = - (8,314 J/mol.K) in 9,51.10-9L/mol.s 600 K 500 K 1,76.105J/mol = 1,76.102kJ/mol 1.5. Gfai thich cac anh hu'ang cua n6ng d6 va nhi6.t do den t6c do phan ling 1.5.1. Thuyet va cham hoat di:mg A - Thuyet va cham giai thich phtiong trinh t6c d6: D6 phan ling hoa hoc xay ra, cac phan tip chat tham gia phan ling (nguyen tU, phan tU, ion, g6c to do...) phai va cham vdi nhau. Nhu vay, tdc cto phdn eeng theyc quyet Binh bdi so va cham gieea cac phan to chat trong 1 dcm vi thol gian. S6 va cham nhi6u hay it lai phu thu6c vao n6ng d6 chat lOn hay nhO. It6t cu6c, t6c d6 phan ling tY 1e thuan voi n6ng do nhu da thay trong phtiong trinh t6c d6 (7-4). Nho rang trong phtiong trinh ay chila tich khong phai t6ng) cac n6ng d6. Vi sao lai nhtt vay? Mo hinh don gian 6 hinh 7-6 d6" dang giai thich di6u nay. - Khong phai moi va cham gifia cac phan tip clew d'an den phan ling. Thuyet va cham hoat Ong cho rang, chi flitting va cham giiia cac phan tip c6 nang Wong 4fi lon, goi la cac phan tit hoat 4 va cham Them 1 6 va cham Them 1 9 va cham Ong, moi c6 th6 gay ra phan ling. Hinh 7.6. T6ng s6 va Nhfing va cham nhti vay dtioc goi la va cham cham giUa cac tau phan có th6 hi6u qua hay va cham du nang A va B /à tich (khOng phai t6ng) cac s6 lacing tido • NhiOt do$ tang có tdc dung lam tang so va chain phan A va B (tuang Ong det nang lu'o'ng, ma thu'c chat la lam tang so-phan tee v6i tich cac Wong c10 ceia hoat dOng. Ca'n htu y: day la nguyen nhan chInh A va B) 29 lam cho t6c dO phan ling tang nhanh khi tang nhiet dO (nhui da thay d vi du phia trutoc, nhiet dO tang 100°C, t6c dO tang 210lan), chit khong phai nhiet dO lam tang chung tang s6 va cham binh thutong (vi ne-u nhur vay, theo tinh toan Ong hoc, t6c dO phan ung chi tang khoang 1,5 Fan, khong phai 210lan, khi nhiet dO tang them 100°C, vol y van bang 2 nhut vi du da dua). - Co the tinh dtioc s6 phan tit boat &Ong hay so va cham du nang lacing theo dinh lukt phan 136 Boltzmann cho cac loaf hat Wong ttt khi 1ST Wang: N* -E,/RT (7-35) N N* - s6 phan tit hoat &Ong. N - tang s6 phan EA - nang Wong can thiet de chuyen 1 mol khi A có nang Wong trung binh tra thanh boat &Ong va goi la nang Wong boat hoa khi A. R - hang so" khi, bang 8,314 J/mol.K. T - nhiet dO tuyet e - cd s6 logarit tLt nhien. Xet phan ling: A (k) + B (k) -> san ph'am Pinking trinh t6c dO: V = k.[A].[B] (7-36) Theo thuye't va cham boat &Ong thi chi nhiing phan tit hoat Ong inch gay ra phan ling, do do: V = 13.[A]*.[B]* (7-37) [3 - he s6 tS7)le. [A]* va [B]* - ming dO cac phan tit hoat dOng A va B. Theo (7-35) thi: [A]*= [A].e-EA/Fa va [B]* [B] e-E,e/RT (7-38) thay (7-38) vao (7-37), ta có: EA+E„ V = 13 [A]* [B]*= RT .[A].[B] = fle-E'RTJAMB] (7-39) 6 day, Ea- nang Wong hoat hod dm phan Ting va. Ea= EA + EB. (7-40) Z* - s6 va cham du nang Wong. Z - tang s6 va cham. Tit (7-39) ta thay lai phtiong trinh Arrhenius (7-31) vdi (3 = A: 30 k= [3.e-E" /RT =EJRT deng thai nhan ra tS'T le va cham du nang Wong tai met nhiet de (kST hieu f) chinh la thila so- ben phai phiiong trinh Arrhenius: Z* e-Ea/RT = f (7-41) Thlia sof cho thay, ca Eava. T cteu anh huOng den tS, le va cham du nang lilting, tfic la Anh huOng den tec do phan ling hay chinh IA lAm thay ct6i hang se t& do k. Khi T tang se khuech dai tY' le va cham có du nang liking vUot qua &foe hang /An nang liking hoat hoa Ea, nhu trinh bAy 6 hinh 7.7 va bang 7.4. Bang 7.4. Anh hvang dm Ea va T der) ty le (f) va chum du nang Ivong de co the phan Ong Ea(kJ/mol) f (a T = 298K) 50 1,72.10-9 75 7,13.1014 100 2,96.10-18 Du lieu 6 bang 7.4 cho thay, vii Ea= 50 kJ/mol - met hang rho nang hong ph6 bien dia nhieu phan Ung, gia tri f (clang là clia tec de phan ikng va hang s6 toe do k) tang g'an gap doi moi khi nhiet do tang 10 de. - Cdu trait phan tee anh hu'C'ing T f (iii Ea= 50 kJ/mol) 25°C (298 K) 1,72.10-9 35°C (308K) 3,31.10-9 45°C (318K) 6,12.10-9 Ea 11/ la va cham du nang Itldng Idn han Nang Mang va cham den tdc dO. Nhu da biet, so va Hinh 7.7. Anh twang cua nhiet do len Sc! cham du nang Wong gifia cac phan b6 cac nang luring hoot hoa phan tii hoat thing có the dan (= nang Ivong va cham). d nhiet cid cao den phan king chi chiem ty le hon T2, t.cf 10 va cham du nang ItiOng de vVot qua EaIOn hon (f) nhO trong tong so va cham. Tuy nhien, ngay ca tS'T le nhO nay et-mg data phan anh dung s6 Wong va cham có hieu qua ma thtic ski gay ra phan king. Con can met yeu te; de va cham du nang liking co hieu lye phan king là ski dinh hiking ching cua cac phan tii khi va cham. Trong pinking trinh Arrhenius k = A.CEJRT, thifa. s6 A ham ch-da yeti to khong gian. Ngvai to goi A la thila s6 tan s6 vdi A = p.Z, trong do Z la tan s6 va cham va p là theta so khOng gian. p ctac trtkng cho moi phan ling, no lien quan den do phiic tap 31 ve mat cau frac cua cac tie2u phan va cham, c6 the coi no nbit la ty le va cham có hie2u qud caa cac phan hoat &Ong du'qc dinh hu'ang thing. Tit cac quan h8 da neu, de dang rut ra bi4u thitc chung cua hang so t6c d6 la sit tIch hop cita cac ye-u to va cham (Z), nang lUong (1) va khong gian (p): k = p.f.Z (7-42) Va cham gifia cac nguyen tit rieng le có p 1, vi cac nguyen tit cd ban c6 hinh cau, khong phu thuOc nhie'u vao hitong. Phan ling: NO (k) + NO3(k) ---> 2NO (k) c6 p = 0,006, tiic la chi có 6 va cham trong 1000 va cham nang lacing duoc dinh Intong khong gian thing de dan den phan ung. Trong cac phan ling hod sinh, cac phan tit nhO can dinh Inking dung tren nhfing \Tung khong gian cuc nhO cUa cac phan tii cue kin (protein, acid nucleic... vii vai tro enzym - xtic tac sinh hoc), p c6 gia tri < 10-6, tile la c6 it ban 1 trong 1 trie2u va cham vii day di' nang Wong tao ditoc san 1.5.2. Thuyet trang thcli chuyin tiep Thuye't va cham boat &Ong clan gian, de hinh dung, nhung khong not ri5 nang Wong hoat hod dUdc sit dung nhU the nao va phan tii hoat dOng bie'n doi ra sao. Nhu da bik 6 chudng 6 (Nhiet dOng hoa hoc), not nang dm 1 118 la tang &Ong nang va the nang cua 118. 2 phan di 6 xa nhau dang chuyen dOng lai gan nhau vii tOc dO rat nhanh, dOng nang cita chting lin, the nang thap. Khi chung tra nen sat nhau, mot phan dOng nang chuyen sang the nang, vi cac dam may electron cila chting day nhau. Tai thai diem va cham, cac phan tii ditng lai, dOng nang cua chting chuy8n thanh th8 nang va cham. Neu the nang va cham khong kin hdn hoac bang nang luting hoat hod Ea, chting bat ra nhu nhfing qua bong ban. Ngtioc lai, khi the nang va cham du lin va cac phan tit lai dinh huong khong gian dung, chting se vuot qua laic day. Hat nhan cua nguyen tit nay but electron dia nguyen tit kia, cac orbital xen phit vao nhau va mat dO electron thay doq, vai lien kat dai ra va 34u di trong khi mot s6 lien ke't moi bat dau hinh thanh, phan tit chat phan ling chuyen dan sang phan tii san pham. O nhfing di8m giao thai trong su6t qua trinh chuyen hod, ton tai khong phai chat phan iing hay san pham ma la cac tieu phan chuyen tie-p vai nhii'ng lien kat khong hoan chinh. Cdc tie'u phan do cuc kST khong en dinh do the nang rat kin, chung chi .ton tai trong khoanh khac khi h8 phan iing dat nang Wong cao nhat. Ngtfoi to goi dO la nhungphitc chat hoat &Ong hay nhiing trang thcii chuyen tie-p cua phan ling, va chting chi hinh thanh neu cac phan tit va cham dttoc dinh huang khong gian thing va nang Wong va cham Ea. Nhu 32 vay, nang luring hoat hoci du'o'c clang cho viec keo dai va lam bie'n clang cac lien ket dat tdi trang thdi chuyen tie' (chung to nhAn biet &toe trang thai chuyen ti6p nhO phep phan tich quang ph6, b6i vi hdu nhu kh6ng the phan lAp dude nhang tieu phan nay). Hinh 7.8 minh hoa don gian cho cac y tren thong qua phan itng gifia methyl.bromid va ion hydroxyl: CH3Br + OH--> CH3OH + Br Can them 2 luu y cho hinh 7.8, nhung clang la chung cho thifc to cac phan ling: - Viec dat tdi trang thai chuyen ti6p van khong dam ban rang phan ling se tien trien tao ra san phAm. N6u lien k6t C-0 tie-p tuc ngan lai va ben them, san phAm dude hinh thanh. Con neu lien k6t C-Br ngan lai va ben hdn, trang thai chuyen tiep se phan huy tr6 lai cac chat ban dAu. Vi th6, theo mau hinh ay, moi phdn zing de'u la thudn nghich. Chit phin Ong Trang thai truck chuygn tiip Trang thai chuy6n tip Trang thai sau chuy6n ttep San phgrn H H Br —CA..., OH 1.` OH H H Br• OH Br' ..OH Br —OH H H H H H H H A 1 Oua trinh phan ang Br` u CH,OH Hinh 7.8. Sc d6 nang lacing ph5n Cmg gicla CH3Br va OH-. Nguyen ter Br tich dien am nen C trong CH3Br tich dien ducng. Cac tau phan ph5n sing vita ph5i chuy6nd6ng du nhanh (d6 dat Ea), vela phi Binh hu'Ong dOng d6 nguyen iii"C6(+)ti6p can duvic 060(tich dien am) ctia OH-, tCi dO bat dau hinh thanh lien kat C-0. d trang thai chuyen ti6p, C du'Oc bao quanh b6i 5 nguyen tzr khac theo kau luting thap tam giac nang lu'ong cao ma kh6ng bao girl co 6 cac hOp chat C binh thtiOng - M6t phan itng thuAn nghich c6 2 nang Wong hoat hoa: Eacho phan thuAn, la hieu so nang ltiOng gifia trang thai da dude hoat hod va chat phan ling; con Ea' cho phan iing nghich, la hieu so nang luring gifia trang 33 thai da duoc hoat hoa va chat san pham. D-6i voi phan ging toa nhiet thi E. < con d6i v6i phan ling thu nhiet thi ngtioc lai, Ea> Ea' (phan the hien 6 hinh 7.8 la phan iYng toa nhiet). N6u bi6t EaIra AH cUa met phan ling, ta có tinh duoc E„' cua phan ling kia va ngticic lai. Vi du: phan 03(k) + 0 (k) 2 02(k) 6) Ea= 19 kJ va AH,), = -392 kJ. Tinh Ea' cila phan ling nghich. Gidi Phan ling toa nhieu nhiet nen mile nang Wong cUa san pham rat thap. De san pham dat den trang thai chuyen ti6p, can cung cap cho san pham met - nang Wong bang AH,,„ + E„, nen Ea' = + Ea= -(-392) + 19 = 411 kJ. So dO nang hiring cua phan ling nay cc') 'clang hinh gieing nhu d hinh 7.8. 1.6. Cd chg phan iffig H61.1 het cac phan ling hod hoc xay ra qua nhieu btioc cd ban la nhfing phan ling so cap. Tap hop cac phcin zing sq cap cte' thanh phdn zing chung duvc goi la cd the phdn zing. Chang han, co ch6 cho phan iing chung 2A + 13' ---> E + F co the Om 3 buoc cc; ban la 3 phan ling sd cap: A + B C + A D C D E + F Phan Ling tong: 2A + B E + F chinh là phan (mg chung Ccic co' the phdn zing va phan tee sal Nguoi ta quy Binh: m6i buck co ban hay m6i phan ling so cap khong tao ra cac but& hay phan ling don gian han nfia. 1V16i boric co ban duoc dac trting b6i cac phan td' so; la so cac tau phan phcin zing trong mji bzddc. Vi du xet phan ling phan huS'T ozon d thucing tang khi quyen. Phan ling chung 203 (k) ---> 302(k) Met co ch6 2 btioc co ban duoc d6 nghi cho phan ling nay la: 34 (1) 03(k) 02(k) + 0 (k) (2) 03(k) + 0 (k) 202(k) Phan ling t6ng: 2 03(k) 3 02(k) Cj buoc (1) chi c6 1 ti6u phan tham gia phan ling nen goi la phcin zing 1 phcin td'. CS buck (2) c6 2 tieu phan tham gia phan ling, quy uoc goi la phdn zing 2 phan td'. Phdn zing 3 phcin td' rat hi6m gap b6i xac suat de 3 ti6u phan va cham ding hic vdi nang Wong day du va dinh hoeing khong gian dung rat be. Phan ling c6 phan tii s6 cao hdn 3 chua dtfoc bi6t. Khac v6i phan ling .chung, phu'o'ng trinh toe da cda 1 phdn (Pig sd cap có the' ctu'o'c suy ra tit he at.); lu'o'ng ciia phdn zing, va bCic phiin (mg bang phan so: + Vi du: Ngtioi to de nghi cd ch6 2 buoc la 2 phan -tang sd cap dui% day cho 1 phan ling chung: (1) NO2C1 (k) NO, (k) + Cl (k) (2) NO2C1 (k) + Cl (k) NO, (k) + C12(k) Cho bi6t: a) Phudng trinh phan ling chung (da can bang). b) Phan of so cua in& biidc. c) Phudng trinh t6c do va bac dm moi phan ling sd cap. Gidi a) Tim phudng trinh phan ling chung da can bang bang cach lay t6ng cac phan ling sd Cap da can bang (1) + (2), duoc: 2NO2C1 (k) 2NO2(k) + C12(k) b) Buck (1) c6 1 phan tit phan ling, vay do la phan ling 1 phan tii. Buoc (2) c6 2 phan ti phan ling, vay do la phan ling 2 phan tii (cling c6 the n6i, phan ling c6 phan tii so-bang 2). c) Pluidng trinh t6c d6 cho cac phan ling sd cap dtioc vi6t: (1) V1= kl.[NO2C1] , phan ling bac 1 (2) V2= k2 . [NO2C1]. [Cl] phan ling bac 2 - Bu6c gied han t6c dO: Tat ca cac phan ling sd cap trong 1 cd ch6 khong c6 cling t6c dO. Bu'o'c cham nhdt so v6i cac bu6c khac ducic goi la buoc gioi han t6c d6 hay buoc quy6t dinh t6c d6 phan ling. Tinh quan trong cua bu'o'c cham nhdt la ci ch8, no dai dien cho toe clo va theo do là dai dien cho phu'o'ng trinh toe do ca phdn zing chung. 35 Tra lai phuong trinh gala NO2va CO (da neu 6 muc 1.2 (phia tren), bang 7.2), phan Ung chung là: NO2(k) + CO (k) -> NO (k) + CO2(k) Neu phan itng chung là 1 phan ling so cap, phuong trinh t6c dO duoc V = k.[NO2].[CO] Tuy nhien, nhii da biet, phuong trinh t6c dO thuc nghiem lai chi ra: V = k.[NO2]2 Vi the, mot co the 2 bUdc dtioc de xuat: (1) NO2(k) + NO2(k) -> NO3(k) + NO (k) [cham, quyet dinh t6c d8] (2) NO3(k) + CO (k) -> NO2(k) + CO2(k) [nhanh] Phuong trinh t6c dO cho 2 budc co ban là: (1) V1= ki.[NO2].[NO2] = k,.[NO2]2 (2) V2= k2.[NO3].[CO] Neu k, = k thi budc (1) la look qUyet dinh t6c dO phan itng. Thtic t6 da xac nhan, dung là k, = k N/A phan ling so cap (1) cham den mitt có the gia thiet phan Ung chung xay ra theo Woe (1) va trong phuong trinh t6c dO kh8ng chfia [CO]. ei day can chti. ST: NO3la. 1 san pham cua bulk (1) Ira là chat phan ling 6 bulk (2). NO3&rig vai tro chat trung gian, khong xuat hien trong pinking trinh phan itng chung da duoc can bang, va s-ct ton tai ciia no là tam thai nhung hoan toan can thik de phan iing xay ra. Khdc voi trang thai chuyen tiep (cac plific chat boat dOng), chat trung gian la cac phan tii voi cac lien kk binh thuang va doi khi chting du On dinh de co lap duoc [giai Nobel Hod hoc nam 2006 dtioc trao cho Roger D. Kornberg, nguai My, v8i nhcing nghien cifu ye qua trinh sao chep thong tin trong cac Bien va su truy6n thong tin do de tong hop cac protein - 6 day, st.f tim thay chat trung gian (mediator) dtioc xem IA mot phdt minh quan trong trong qud trinh sao chep]. - Thiet l4p mot cd the phdn (mg. Nghien cuu va de xuat co the cho 1 phan tang phai dam bao 3 tieu chuan: 1/ Tang tong cac phan ling so cap phai cho phan itng chung xay ra th-qc trong tIrtic te. 2/ Cdc phan ling so cap phai có kha nang xay ra, nghia là chi g6m phan ling 1 phan tit hoac 2 phan tit. Phan ling 3 phan tit duck xem IA rat it by vong xay ra. 3/ Co the phan itng phai phis hop voi phuong trinh t6c dO (hay dinh luat t6c dO) duoc xdc dinh bang thuc nghiem. Co 2 loai co che: bUoc dau cham va buck dau nhanh. 36 a) Cci the vdi bu'dc deiu ch(cm. Phan ling NO2-I- CO a phan tren da la mot vi du cho truong hop nay. Xet them phan ling chung: 2NO2(k) + F2 (k) -+ 2NO2F (k) Pinking trinh teic d6 thiic nghiem: V = k.[NO2].[F2] \fa co c14 hien nay dtioc chap nhan la: (1) NO2(k) + F2 (k) -> NO2F (k) + F (k) [charn,quyet dinh t6c (2) NO2(k) + F (k) -> NO2F (k) [nhanh] Co the nay phit hop vol 3 tieu chuan thiet lap, vi: + Tang (1) + (2) cho pinking trinh phan ling chung. F la chat trung gian khong xuat hien trong phan ling chung. + Ca 2 bride clia co the de'u la cac phan ling 2 phan tii nen thoa man tieu chuan this 2. + Phuong trinh t6c d6 cila phan ling cham c1 btiOc (1) V1= ki.[NO2].[F2] Au hop vdi pinking trinh t6c d6 thtic nghiem. Theo do, buck (1) la Woe guy& dinh t6c do cua phan ling chung. Hinh 7.9 cho thay so d6 nang ltiong cua phan ling NO2- F2. Nang Krung Trang thai chuye'n ad.!) Ea (buoc 2) 2NO2+ F, Chat phan irng NO2F + F + NO, nhanh 2NO2F Qua trinh phan irng Hinh 7.9. Sc d6 nang krong cho co ch6 2 buck caa phgn (mg NO2- F2. M& butic trong co ch6 co pink ch6t hoat Ong rieng cita n6 (k)Y hi6u *). Butic (1) ch0m, giOi han t6c c16 phAn (mg do Eacoa nO 16n han bu'dc (2) b/ Cd the vai bu'dc deiu nhanh. Xet vi du phan ling NO - 02 . Phliong trinh phan ling chung là: 2N0 (k) + 02(k) -> 2NO2(k) 37 Phtiong trinh tic do thiic nghiem: V = k.[N0]2.[02], vA co ch6 &foie de xuat là: (1) NO (k) + 02(k) NO3(k) [nhanh, thuan nghich] -1 (2) NO3(k) + NO (k) 2NO2(k) [cham, quyeI dinh toc d()] Phuong trinh t6c do cUa 2 phan ling so cap 6 2 bu6c duoc viet: (1) V1 (thuan) = k1 .[NO].[02] va = k_1. [NO3] 6 (2) V2 = k2. [NO3] • [NO] Chit phan ling 6 buoc (1) nhanh, cho nhieu san pham (la chat trung gian NO3) nhung lai tieu thu chAm 6 bulk sau (nen goi là phan fing "c6 chai"), vi the no phai là phan ling 2 chieu de chuyen 136-t san pham tra lai chat &Au. Kiem tra co ch6 theo 3 tieu chuan thay: + Tong (1) + (2) thing IA cho phtiong trinh phan ling chung da can bang, chat trung gian .(NO3) khong xuat hien trong phuong trinh chung. + ca 2 bli6c la cac phan ling 2 phan tii, nen kha thi. + Plniong trinh tic do ciia phan ling cham V2= k2.[NO3].[NO] cho thay khong phn hop voi phuong trinh Vic do thiic nghiem da cho. Tuy nhien, vi blioc (1) là thuan nghich, 6 trang -alai can bang V1= V., hay k1 .[N0].[02] = k_1 .[NO3], nen [NO3 ] = kk ' [NO][02 ]. Th6 [NO3] vao i pinking trinh tic do clia. bueic (2), thu duoc: V2= k2 •k [NO]2[02 ] = k.[NO]2 [0,]. Phtiong trinh t6c do 6 btioc (2) cham dd the hien phuong trinh tee do thiic nghiem cua phan ling chung. VAy, cd ch6 dlidc de xuat la dung. Phan ling Om nhieu bti6c trung gian, hoac cling met Inc di theo ca 2 co ch6, duoc goi là nhfing phan fing.phlic tap, ph6 'Dien nhat là cac phan ling n6i ti6p, song song, day chuyen, thuAn nghich... 1.7. Chgt xuc tac thnc d'Ay to-c cho phan ling — Chdt xi c tac la chdt lam tang tdc clo phcin zing va chive hoan nguyen sau qua trinh phan zing. Xac tac, hay sit xac tac, là hien Wong thlic day tic de phan ling duesi tac dung elm chat xnc tac. (Chat lam giam t6c de phan ling dei khi duoc goi IA chat xtic tac am. Tuy nhien, nen goi là chdt zic che'hon la chat xtic tac). 38 Nang ltrong (Ihuo) khOng xtic tac ChSt phan (mg Ed (thuan) co xac tac H pu khOng xtic tac Ea (nghi co xuc tac duct xuc tac Ea (nghich) khOng xtic tac San pham Qua trinh phan ting Hinh 7.10. So do nang luang ph5n Cing cela mat qua trinh cluac xuc tac va kh6ng duac x0c tac. Chat xtic tac thik ddy teic d6 phan ling bang cach chuy6nca the 1 buac thanh co ch6 2 buck theo con du'ang nang Itiang th6p hon. TOc d6 ph5n Cing thuOn va nghich deu tang mat luting nhu nhau, nen chat )(tic tac kh6ng anh hu'ang d6n toan bij phan ung chung Ngay nay, khoang 90% qua trinh san xuat hod hoc phai sit dung chat xtic tac. Hang nam, chi rieng tai Hoa Ky, hen 2,5 trieu tan chat xtic tac &toe sit dung trong tong nghiep. Tuy nhien, thien nhien moi. la "Ngtioi si..1 dung chat xnc tac: mot to bao vi khuan den gian nhat clang dung den hang ngan chat xtic tac sinh hoc goi la enzym de tang t6c d5 cac phan ling t6 Joao can thiet cho su 1\/18i chat xtic tac có 1 cach rieng biet de thuc hien chic nang cua minh, nlaing v6 co ban thi chat xac tac lam tang tot cho phan zing bang cach ha thciP nang lu'dng hoot hoci, do do lam hang s6 t6c do ldn hen va to-c d6 phan ling cao hen. Dieu nay duoc the hien tren gian dO hinh 7.10. - Hai dac diem quan trong cila chat )(tic tac: 1/ Chat xlic tac lam tang to-c d6 ca phan iYng thu4n va nghich. M6t phan ling c6 chgt xtic tac khong cho nhieu hen s6 san pham nhung no cho ra san pham nhanh hen nhieu. Can nhan ra cac y nghia: + M5t phan itng c6 AG > 0 thi chat xtic tac clang khong the lam cho no xay ra citfOc. BEd chgt xuc tac con nguyen yen sau phan itng thi clang khong gop ich gi cho thay dOi. AG. 39 + Chat xiic tac khong lam thay doi trang thai can bang cua phan ling ma chi lam cho can bang dat duoc nhanh hon. LST do la, chat Kik tac lam tang t6c d5 mot ltidng nhu nhau doi vdi ca phan Ting thuan va nghich, nen hang s6 can bang ciia phan ling khong thay 2/ Chat xac tac ha thap nang luong hoat hoa bang each tao ra mot cci the phan ling khac - mot con &tang nang Wong m6i thap hon. to goi do la cci the cilia qua trinh xuc tac. Gia sii mot phan ling xay ra theo cci ch6 1 bii6c vdi phan tii so-bang 2: A + B --> san pham [cham], doi hOi Ea Co chat xuc tac thi phan ling chay theo cd the 2 biidc: (1) A + xdc tac C [nhanh], doi hOi Eal (2) C + B san ph'am + )(tic tac [nhanh], doi hOi Eat Chat ink tac dttoc hoan nguyen (h5i sinh) va con &tang nang Wong mdi co Ea, < Eava Ea2 < Ea. - Co 2 loai )(tic tac la xuc tac d6ng the va xtic tac di the. + Xiic tac d'Ong the: chat xuc tac ding pha vdi cac chat phan ling. Noi cach khac, chat Kik tac ciing ton tai duoi dang dung dich (theo nghia r5ng, killing chi la dung dich lOng) vdi hiSn hop phan Hau het chat ink tac do'ng the la chat khi, chat 'Ong, hoac chat ran tan duoc trong dung dich. + )(tic tac di the: chat xtic tac va cac chat phan ling i cac pha khac nhau. Xtic tac di the thuang la chat ran Wong tac vdi cac chat phan ling ii the khi hoac lOng. Vi phan ling xay ra tren be mat chat ran, nen chat )(tic tac di the thuOng phai c6 vi ng be mat rat lon (gifla 1 - 500 m2/g) de hap phu, do do lam tang n6ng d5 cac chat phan ling tren be mat. 6 dO, su xiic tac lai din ra theo cci the chung nhu da not tren. Nhieu chat ran c6 tinh hap phu manh (nhu than hoat), cac kim loai thu5c nh6m VIII B nhu Pt, Ni, Pd, Ru, Os, Ir..., hay cac hop chat ciia cac kim loai chuyen tiep khac (nhu Mn02)... la nhung xnc tac di the quan trong. Xtic tac enzym Co hang ngan phan ling rieng re xay ra trong moi t6 bao song. Nhieu phan ling la nhcing bien d6i hod hoc plific tap, nhung chting van din ra hoan hao diidi dieu kien ang d5 dung dich thap, nhiet do va dp suat binh thuang. T6c d5 cua Bing phan ling dap tra nhip nhang vdi t6c dO cua cac phan ling khac, vdi tin hieu tii nhang t6 bao khac, va ca vdi nhung bien ap tit moi truang. Thiic ra, rad phan ling trong su dieu hoa hod hoc kST dieu ay &foe xiic tac b6i. 1 enzym dac hieu, dO la 1 protein ma chfic nang xtic tac cna no duoc hoan thien qua qua trinh tien hod. 40 Enzym c6 cau trtic 3 chigu phiic tap, khoi hieing mol thay d6i of 15000 den 1000000 g/mol. Tren be mat ciia 1 enzym c6 1 diem dac biet goi la vi tri hoat dQng, mot "ke niit" phan tip ma hinh the dm no dtioc quyet dinh b6i sti sap xep cac chuoi aminoacid c6 lien quan den chiic nang xuc tac dac hieu. Khi cac phan tif chat phan ling (goi la co chat) va chain vdi vi tri hoat dong, phan iing hod hoc xay ra ngay. Vi tri hoat Ong chi la mot phan nha be ciia be mat enzym - giong nhti mot h6 nh6 dtioc dao tren stun nth, nhung c6 the chfia ca mot s6 nh6m amino acid tii nhung \Tung xa xoi cila protein. Trong hau het cac tniong hop, co chat lien ket voi vi tri hoat Ong thong qua cac ltic lien ket phan tit cac lien ket hydro, lien ket Wang chic va cac llic yeu khac. Enzym co cac dac tinh cua ca ).co.c tac Ong the va di the. Giting )(tic tac di the, vi so voi Co chat, hau het cac enzym co kith -dui& kh6ng 16 va thilang gan voi mang to bao. Tai vi tri hoat diing tren be mat enzym, 1 phan tii chat phan ling dttoc c6 dinh tam th6i Witt la bi hap phu) de cha "doi tac" phan ling con 14i se dap xu6ng gAn. Gi6ng xuc tac d6ng the, vi cac nhom amino acid dia enzym toting tac v6i co chat theo ski ph6i hop da cap c6 tao thanh cac hop chat trung gian. Cac enzym la nhting chat xtic tac c6 hieu qua. 14 01-Laing. Chi can lay 1 vi du v6 thug phan ure: (NH2)2C=O (aq) + 2H2 0 (1) + (aq) 2NH4+ (aq) + HCO3-(aq) Trong moi truang ntioc, o nhiet d6 phong, khi kh6ng c6 xuc tac, hang s6 t6c do cua phan Ting la 3.104°s-1(phan ling bac 1). Ciing trong dieu kien khi c6 mat enzym urease, hang s6 t6c d6 la 3.104s-1, tang mot tram ngan tg (10k') lan. Noi chung, cac enzym lam tang tee dQ phan ling khoang 108- 1020 gia tri ma cac rtic tac khong sinh hoc kh6ng the nao dal toi. Cac enzym con civic kST . dac hieu, moi phan ling chi dtioc xtic tac bai 1 enzym rieng. Urease chi )(tic tac thug phan ure, khong con enzym nao khac trong s6 vai ngan enzym trong t6 bao xtic tac dtioc cho phan ling do. Dac tinh phi thttang nay c6 dtioc la do cau true dac hieu cua enzym, dac biet la vi tri hoat Ong. Tinh dac hieu cht6c giai thich theo mo hinh "6 khoa va chia khod": 6 khod la vi tri hoat Ong dac hieu, chia khoa la co chat. Vai thap nien gan day, mo hinh 6 - chia cling nhac dtioc thay bang m6 hinh "tay trong gang": tay•là co chat va gang la vi tri hoat Ong. Mo hinh sau cho thay enzym c6 bien d6i cat' tnic khi co chat dap vao vi tri hoat dong, ski tiep )(tic gan ket tay - gang tra nen hoan hao hon. DOng hoc ciia )(Ile tac enzym co nhieu diem chung v6i xilc tac thong thliang. Trong phan ling khong )(tic tac, t6c do phan ling phu thu6c n6ng do chat phan Ting. Trong phan ling co xtic tac, t6c d6 phan ling 14i phti thu6c vao 41 n6ng d6 chat trung gian (chat phan ling - xdc tac). Trong truang hop có xtic tac enzym, co chat (S) va enzym (E) tao phlic hop trung gian ES ma ang c16 cua no se quyet dinh t6c d6 tao thanh san pham (P). Co the chung cho tat ca cac pilau ling có >clic tac enzym là theo kigu "buoc dau nhanh" (nhit da trinh bay phla tren): (1) E + S ES [nhanh, thtta'n nghich] (2) ES P + E [cham, quy6t dinh t6c dO] Enzym sit dung nhigu cd ch6 de tac d6ng den lien ket gifia cac nguyen tit nham bien d6i cd chat thanh san pham (vi du nhu lam cac lien ket ngAn lai de bgn hon; hodc dai ra de yeti di va dlit; be tong lien kgt trong co chat de tiep xtic hoan hao "tay - gang" do dO phlic hop trung gian ES on dinh va ha thap nang Wong hoat hod; hodc cho di proton (H+) de lam tang t6c do htioc guy& dinh t6c d6 phan 2. CAN BANG HOA HOC 2.1. Dal ctidng Tat ca cac phan ling co the chia tuning d6i thanh hai loci: + Phdn ang mot chi& la phan ling tier' hanh den clung, den khi ma mot hodc tat ca cac chat ban dau da tac dung het de tao thanh san pham. Vi the, nguai to con goi la phan ling hoan toan hodc phan itng khong thudn nghich. VI du, phan Ung chdy cua propan: (k) + 502(k) —> 3CO2(k) + 4H2 0 (k) Phan ling phan hu.S'T kali permanganat 6 nhiet d6 cao: 2KMnO4(r) K2MnO4(r) + MnO2(r) + 02(k) Ph-an Eng phan ht6'7 hydro peroxyd 6 rihiet d6 thtthng: 2H2 0;- (1).. 2H2 0 (1) + 02(k) + Phdn ring thudn nghich la phan itng trong nhfing digu kien xac dinh c6 the tien •hanh dOng thai theo hai chigu ngti6c nhau, nghia là cac chat dau tac dung voi nhau cho ra san pham, thi ciang trong digu kien ay cac'ch 'at - san pham tac dung'voi nhau de tao thanh chat dau. Vi du: N204(k) -7= 2NO2(k) C (r, 'long dO) + H2O CO (k) + H2(k) H2 (k) + 12(k) 2H1 (k) Nhu da biet, theo thuyet trang thai chuyen tiep, moi phan itng dgu la thudn nghich. 42 - Vi phan iing hod hoc rat khdc nhau v6 t6c do, nen cluing cling khdc nhau ye ,d6 Hai khia canh nay là khac nhau. MOt phan iing nhanh có the tien trien hoar' toan hay chi mot phdn v6 phia san pham. ChAng han, vOi. HC1 1M, hdu het tat ca cac phan to acid dien ly thanh ion. Vali CH,,COOH 1M, chi dlidi 1% so-phan to acid dien ly thanh ion. Tuy nhien, ca 2 phan itng xay ra rat nhanh va hoan thanh chi khoang dtioi. 1 gidy. Thong tu, mot s6 phan itng cham cu6i ding cho mot Wong lOn san pham, trong khi nhang phan ling khdc cho rat it san pham. Chang han, sau vai nam 6 nhiet dO ph6ng, thep 6 mot binh ,dung nu& se bi gi, nhung nueic trong binh khong bi phan WT. Diem Wu y 6 day la cac nguyen tac dOng hoc cua trang thai can bang dp dung cho cac khia canh khdc nhau cua mot phan fing. Tdc do caa mot phan zing - la n6ng dO cua san pham tao thanh trong mot don vi thai gian - chic yea phu thuOc veto su khac nhau ve nang lifting cac chat ctdu vet trang thcii chuyen tiep. Mt& do caa phan a'ng - la neng do cua san pham khi khong con quan sat dtfoc sit bien doi vi mo nao nita - phu thuOc chic ye-u veto su' khcic nhau ye nang lu'o'ng giiia chat ctdu va san phdin. - Khi luring cac chat ddu mat di theo phan itng thuan bang Wong cua cluing dtioc tao thanh tit phan ling nghich, ta not phan iing da dat toi trang thcii can bdng (TTCB). Cdc qua trinh hod hoc thuan nghich (la nhang qud trinh th-qc, khdc voi qua trinh thuan nghich nhiet dOng chi la gia dinh) bao gem: cac phan fing thuan nghich d6ng the hay di the; s-ki dien ly dia acid, base; sv thuY phan cac mu6i; sit phan ly cila phfic chat; qua trinh hoa tan; cac qua trinh chuyen pha... deu thiet lap nhang TTCB. Nhiem vu co ban trong nghien diu TTCB la xd.c dinh thanh Oar" hi:in hop-khi can bang va cac yeti to anh hoeing den can bang. 2.2. Phudng trinh clang nhiet Van't Hoff. Hang so can bang - Tit phudng trinh [(6-69) - chtiong 6] va xet ■ )i dieu kien P, T khong doi, ta có the rut ra tieu chudn tu' dien bien vet gidi han caa cac qua trinh hoci hoc ceing nhu' chuyen pha dG 11.tdni (7-43) pti: the hoa cila ca.'u dni: bien thien s6 mol cua caT-o tit i Wong ung trong he. Tit do, có the tinh AG = !d i n; (7-44) 43 Chang han, d6i vol phan ttng chung trong he khi 1ST Wang (cho gon, chi xet Om 4 chat): aA + bB -> eE + fF (7-45) thi: AG = G1sp1- Gicni= (euE+ fuF) - (ap.A+ buB) rut ra: AG = [SP] - t.t i[CD] (7-46) va d dieu kien chuan: AG" = DI;)[SP] - j4[CD] (7-47) Vay a dieu kien clang nhiet (fang ap: Neu II;[CD] > 1p.;[SP] = AG < 0 , phan itng tu phat (tit trai sang phai). Neu Di;[CD] = µ; [SP] = AG = 0 , phan itng d TTCB. - Thay = RT1nPi[phticing trinh (6-64) vao (7-46)], thu AG = [e (t4 + RT1nPE ) + f + RT1nPF - [a (AA+ RT1nPA ) + b (µCB + RT1nPB ( e 13E F Pt\ + f 14' - 1_1 (,‘ ) + b ti;3 )+ RT In PAa• PBb G`p GL) AG = AG" + RT In E Pe= AG" + RT1nQp 13: • PI13 9) bd (7-48) ei day PA, PB, PE, PFla cip suet rieng phcin ban deiu bd) cua khi A, B, E, F trong he phan fing d nhiet d6 T; a, b, e, f la he s6 hop thfic (he s6 ty Wong) PeE . P t cuaF cac chat A, B, E, F trong phan ling; Q,,= goi là bie'u thdc tcic Da Db 1- i6k IB bd dung khoi, lu'dng (tinh theo ap sub."-t rieng phdn) hay thu'o'ng so ctia phiin Ling (q7 s6 gifia san pham chat ddu) ltic ban ddu. - Gia tri bang s6 cua Qpthay doq sal trong qua trinh phan itng. Khi he dat ten TTCB nhiet de? T), thanh phdn cac chat khong Nen cr6i nila, Q1, = const = K1 , vay: 44 ( e \ PE • PF Kp (7-49) PA3• PBbcb Kp la hang s6 can bang tinh theo dp suat rieng phan cita cac chat trong phan ling (7-45) clang thuan nghich d TTCB, lac nay t6c do phan ling thuan bang t6c d6 phan ling nghich: aA + bB eE + fF (7-50) CS TTCB, AG = 0, plitidng trinh (7-48) tra thanh: (e P t 0 = AG° + RT1n . E P F iBich AG° = -RT1nKp (7-51) Thay (7-51) vao (7-48) va sap xep lai, to cd: (Q AG = RT(lnQp = RT1n - lnKp) K p (7-52) Chit suat rieng phan cua cac chat trong bieu thlic Qp, Kp dell dung don vi atm. Cac phudng trinh (7-48); (7-49); (7-51) va. (7-52) la nhiing clang cita phu'o'ng trinh deing nhi0 Van't Hoff. - M6i lien he giaa Kpva cac hang s6 can bang Kc, K„, KN + Ap suat rieng phAn aim khi lY Wang lien he vdi ang d6 qua phudng trinh: Pi = n1. RT V = CiRT ni: S6 mol chat i R = 0,0821 atm.L.mo1-1.K-1 T: Nhiet 4 Kelvin V: The tich dm he phan fing (L) Ci : Ming do cau tit i trong he (mol/L) Thay tong thfic cua Pitinh o TTCB vao (7-49), thu cludc: (ce rf Kp = Ca A 13/ CB (RT)An = Kc (RT)'" (7-53) 6 day, Kcla hang s6 can bang ciia phan itng throe bi6u din qua ang do mol/L: 45 Kc = (C;, CtF ( [E]e [F]t \ (7-54a) [A]a[B]b, /cb Ca Cb \ A B Lb CA, CB, CE, CF la niing d6 cac chat 6 trang . thai can bang (mol/L). An = (e + f) - (a + b) (7-54b) do la hi6u so gifia tong cac he s6 ty Wong cac chat khi tao thanh va tong he s6 tST Wong the chat khi ban dau trong phan da cho. Chu 51 rang, Kp chi phu thu6c nhi6t d6 (vi phu thu6c nhikt d6); va theo (7-53) thi Kccang chi phu thu6c nhikt d6. Bi& thric (7-54a) la Dinh luat bac dung khoi luvng do C. Gulberg va P. Waage hai nha hod hoc Na Uy thi6t lap nam 1867 khi nghien cifu t6c d6 cua phan 1mg thuan nghich. + N6u thay Pi= nPtow, [pInfong trinh (1-21), chiidng 1] vao (7-49) thi: ni 1=1 voi K„ = Kp= K,, e t nE •nF a nb ( Prying An n ' )cb (7-55) (7-56) \n A ' B ch ni- so mol khi i 6 TTCB. En, - tong s6 mol khi c6 mat trong he phan tang khi can bang (k6 ca khi "trd" khong tham gia vao phan Pidug - ap suat tang Ong cila he hie can bang. Pi- ap suat dia khi i hic can bang. Pt8. „, va Piclang don vi atm. Theo (7-55), lc ngoai ski phu thu6c nhi6t d6 Wong tit nhtl Kp, con phu thu6c vao ap suat tang va tong so mol khi caah6 khi can bang. + N6u thay Pi= Ni.Pto,„g [pluiong trinh (1-22), chtiong 1] vao (7-49) to c6: / e r E F KN, (13 An (7-57) 0\11.1\11:3,6 ton Kp = ■ • teing ) el) NeE .N voi KN= (7-58) 1\l'A .Nbir3jth 46 Ni- n6ng dO phdn mol cita khi i trong he phan ling hic can bang, vdi NT;= ' [theo (1-21), chuong 1]. Theo (7-57), KN phu thuOc nhiet dO va Pte;ngcila he khi can bang, nen ngu Ptis,ng(6 TTCB) = 1 atm, thi Kp= KN. Cac hang so can bang lien quan v6i nhau nhu sau: i p All ' uing An (7-59) Kp = Kc.(RT)'" = Kn. v, \ L n i Jeb = KN.(13t6ng )cb Khi An = 0, nghia la so mol khi 6 2 ye dia phuong trinh phan ling bang nhau, thi: Kp= Kc= K„ = KN (7-60) 2.3. HAng so can bang K va bieu attic tac dung khOi ltidng Q Thuong so [san pham]/[chat dau] bigu thi thanh phan cua he phan ling 6 thai digm xet goi la tdc dung khoi lucing (= BTTDKL) va ky hieu la Q. Khi Wong chat duoc bigu din qua mot dai ltiongcu thg (Pi, C1 , 1\11 ) thi Q duoc vigt Wong iing. ChAng han vigt Q tinh theo ap slat rieng phan va tinh theo n6ng dO mol/L cho phan ling (7-45): QP = ( pe .p r E F PApb A • bd va Qc r [E]e .[F]t \ ['A]a• [Br ibd (7-61) Nhu da bi6t, 6 trang thai can bang thi Q = K, bigu thfic Q luc nay goi la bigu Ur& cila hang s6 can bang (= BTHSCB) va duoc vigt cho Kp, Kcnhu 6 (7-49), (7-54a). Vay, K la gia tri dac biet cUa Q khi cac s6 hang cUa san pham va chat dau dat thioc gia tri cua chting 6 TTCB. (Tif day, to chi dg cap dgn Qp, Kpva Qc, Kcla 2 cap dai Wong thuang duoc sii dung). Hang sec can bang K chi phu thuOc vao nhiet dO va ban chat cita cac chat tham gia phan iing chic khong phu thuOc vao luong chat ban dau cita Digu quan trong nhat la K tlidng doing voi mot ty so nhat dinh giiia cac so hang bigu thi Wong chat san pham va chat dau 6 TTCB tai mot nhiet dO. Theo do, K cho bigt in& dO hoan thanh cua mot phan iing. K nh6, phan iing tign trign it vg phia san pham khi dat TTCB. K rat ion, phan iing dat tdi TTCB voi hau hgt chat dau bign thanh san pham. K trung gian gifia hai infic tren thi d TTCB van con có mot tong dang ke ca chat ddu va san pham. Nh6 47 rang, d TTCB, phan ling thuan nghich van din ra (6 mile dO vi mo phan nhung t'6c d6 dia cluing bang nhau (6 mile dO vi mo, to khong con xac dinh duoc sit thay d6i nao ve cac th6ng s6 trang thai T, P, ni...). D6 la trang thai can bang Ong. 2.4. Chi6u Infeing va gi ii han cua phan iing Lam sao de biet mot hiSn hop bat kST cua cac chat phan ling va san phdm tai mot nhiet dO se tien trien theo hitting nao (theo chigu thudn hay chigu nghich?) de dat tdi TTCB? Co 2 cach de dii doan: so sanh cac gia tri Q vb. K hoac xet dau ciia. AG. - So sanh cac gici tri Q va K. Nguoc voi gia tri K là hang so/6 in& nhiet gia tri Q bien thien, c6 the nh6 licin hay lon hdn K va khi he dat tdi TTCB thi bang K. CO the xay ra 3 truing hop khi so sanh Q va K. 1/ Q < Kthi inau s6 (chila cac s6 hang chat &du) lon hdn so vOi tit s6 (chila cac s6 hang san pham). De Q Wong &Ring voi K thi mau so phai giam va tit s6 phai tang. Noi each khac, phan ling tien trien ve ben phai (chigu thudn) tao thanh san phdm nhigu hdn cho tdi khi dat TTCB, d do Q = K. 6 tritOng hop nay chigu phan ill-1g la: chat dau --> san phdm. 2/ Q > Kthi tit s6 (san pham) se giam va mdu s6 (chat ddu) se tang cho den khi dat TTCB. Vdy phan ling se tien trien sang trai (chigu nghich) vg phia tao ra chat dau. 6 day chigu phan ling la: chat dau san phdm. 3/ Q = K.Tinh hueng nay xay ra khi nOng dO (hay ap suit) eila chat dau va san phbm co cac gia tri a TTCB. Vi vdy, khong c6 Men d6i thuc nao xay ra. (3 day phan ling duoc viet: chat dau san phdm. - VI du: Cho phan ling: N204(k) 2NO2 (k) , co Kc= 0,21 6 60"C, tai mot thai diem trong qua trinh phan itng. Ket qua phan tich cho biet: [N204] = 0,12M va [NO2] = 0,55M. Vay phan Ung se tien trien theo hitting nao ve TTCB? Gidi Viet BTTDKL Qrva tinh: Qc = [NO2 ]2= 0,55 2 = 2,5 [N2 04 ] 0,12 Vi Q,. > Kr, phan itng chiia dat TTCB va se tien trien ve phia trai cho den khi Qr= Kr. 48 - Xet gici tri AG. Tr6 lai phuong trinh clang nhiet Van't Hoff (7-52) va viet Q, K du6i dang khai quat: AG = RT (lnQ - InK) = RT1n(Q/K) (7-62) Theo day, ta c6 the du doan chieu huong cUa phan + Neu Q/K < 1 -> ln(Q/K) < 0: phan ling theo chieu thudn (vi AG < 0). + Neu Q/K > 1 -> ln(Q/K) > 0: phan ling theo chieu nghich (vi AG > 0). + Neu Q/K = 1 -> ln(Q/K) = 0: phan ling 6 TTCB (vi AG = 0). Moi quan he theo phuong trinh (7-62) c6 nghia gi? Q dai dien cho ang d6 (hay alp suat) cua cac thanh phdn cUa he tai bat ky thoi diem nao trong qua trinh phan Ting, trong khi do K dai dien cho cac gia tri nay khi phan Ting dat toi TTCB. Phtiong trinh (7-62) chi ra bien thien nang Wong tti do Gibbs ciia he 6 mot trang thai khi &du Q nao do va nang Wong tu do Gibbs dm he 6 trang thai ket thuc K. Doi vdi he 6 TTCB, Q tra nen bang K, vi the AG = 0. Noi each khac, a TTCB khong xay ra su bien &Si nang ludng, he da giai ph6ng tat ca nang luring tu do Gibbs cUa no trong qua trinh dat den the can bang. D6 lon cUa AG phu thu6c vao ski khac nhau vg d6 16n dia Q va K. Bang each chon cac gia tri 6 trang thai chuan cho Q, ta thu duoc bien thien nang Wong Gibbs chuan (AG°), la tong nang Wong Gibbs giai phong ra khi di diem bat dau dia trang thai chuan den diem ket thlic tai trang thai can bang. Khi moi Ming d6 Id 1M (hay moi alp suat la latm), Q bang 1, nen: AG°= RT1n1 - RT1nK hoac AG°= -RT1nK (7-63) (Thong to nhu phudng trinh (7-51) da duoc rut ra cho Kp phia tren) Moi quan he rat quan trong nay cho phep chimg ta tinh Nen thien nang Wong Gibbs chudn (AG°) cua mot phan ling tii hang so can bang K va ngtioc lai. Vi AG°c6 quan he logarit v6i K, nen moi ski thay doi nh6 v6 gia tri AG° cling anh huang lon den gia tri cUa K. Bang 7.5 cho biet cac gia tri cua K Wong ling voi khoang Wen thien cac gia tri AG°. lAtu ST rang, AG°tang during, hang s6 can bang K tang nh6, nghia la phan ling dat den trang thai can bang I/6i it san pham hdn va nhieu chat ban &du hdn. Khi AG°tang am, phan -tang dat toi trang thai can bang v6i nhieu san pham hdn va it chat ban dau hdn. VI du, AG°= +10 kJ, K = 0,02, dieu clo c6 nghia la so hang san pham nh6 hdn 50 l'an s6 hang chat ban dau. Nguoc lai, neu AG°= -10 kJ, so hang san pham 16n hdn 50 lan so-hang chat ban dau. 49 Bang 7.5. Tuzing quan gicla ziG°va K 298°K AG° (kJ) K Y nghia 200 1 x 10-35 Co ban khOng c6 phan ang thuan; phan 100 3 x 1018 ang nghich coi la hoar' toan 50 2 x 10-9 10 2 x 10-2 1 7 x 10-1 Phan timg thuan va nghich cá toc do 0 1 bang nhau -1 1,5 -10 50 -50 5 x 108 -100 5 x 101 ' Phan (Mg thuan coi hoan toan; co ban -200 1 x 1035 kh6ng có phan ang nghich Tat nhien, hall het cac phan ring khong bat dau veil tat ca cac thanh phan trong dieu ki5n chuan dila no. Bang each thay mii quan 115 gifia AG°va K [phridng trinh (7-63)] vao bi5u thric AG [pinking trinh (7-62)], cluing ta thu dridc -bi5u thric có the alp dung cho bat di nang d6 khai dAu nao: AG = AG°+ RT1nQ (7-64) - Bai than dp dung pinking trinh (7-63) va (7-64). Tra lai vi du dd bie't ve sif oxy hoa SO2trong san xuat acid sulfuric (chtiong 6): 2S02(k) + 02(k) 2S03(k) O 298°K, Vic d5 phan ling qua cha.m, vi the ngridi ta tien hanh a nhikt d5 cao hdn. Hay: a) Tinh Kpa 298°K va a 973°K? Cho biet AG °2,8= -141,6 kJ/mol va AG y73= -12,12 kJ/mol. b) Trong binh kin: Pso,= 0,50 atm; P0,= 0,010 atm; Pso, = 0,10 atm girl 25°C va 700°C. 6 ca hai nhi5t d5 nay, ngu phan ring xay ra thi lien den trang that can bang theo chi5u nao? c) Tinh AG dial15 a cau b tai m6i nhi5t d5? - Gicii: a) Tinh Kpd 2 nhi5t d5: dp dung ph-acing trinh (7-63) + 298°K, s6 mu la: 50 -AG°/RT = ( —141,6 kJ / mol x 1000 J /1 kJ 8,31 J /mol.() K x 298 °K = 57,2 Vay, Kp = e57'2= 7.10' + C 973°K, s6 mu la: -AG°/RT = ( —12,12 kJ /mol x 1000 J /1 kJ 8,31 J /mol.() K x 973 'K = 1,5 Vay, Kp = = 4,5 b) Tinh gia tri cua Qp: D2 so3 0,102 • QP = Ps D = 4,0 jp so2 x 02 0,502x 0,0 1 0 + Vi Qp < Kp d ca hai nhiet do nen c6 nhigu SO3tao thanh hon, cho den khi Qp Wong ducing vdi Kp. Tuy nhien, a 298°K, phan itng hAu nhti chuygn vg ben phai. (chigu thuan) truck khi dat trang thai can bang; trong khi a 973°K, phan iing chi dich chuygn mot chat sang chigu thuan. c) Tinh AG d trang thai khong chuan: + Cj 298°K la: AG298= AG 298+ RT1nQp = -141,6 kJ/mol + (8,31 J/mol.°K x 1kJ/ 1000J x 298°K x 1n4,0) = -138,2 kJ/mol + CS 973`)K la: AG973 = AG ,()73 RT1nQp = -12,12 kJ/mol + (8,31 J/mol.°K x lkJ/ 1000J x 973°K x 1n4,0) = -0,91 kJ/mol Thao luan kgt qua: d6i vdi cac ap slat khi ban d'au ii 973°K, qua trinh chi vita du xay ra tit phat (AG = -0,91 kJ/mol). Tuy vay, to van tign hanh phan iing nhiet d6 cao ding vOi. mot chat )(tic tac a tang ma.nh t 6c do phan ling trong thvc to san xugt (mac du san Wong cao hdn d nhiet do thap, nhung t6c do phan ling lai qua cham). — Thuat ngit tit phat va khong ttt phat d6i voi cac phan itng thuan nghich Xet phan itng hai chigu tang quat A B, c6 hang s6 can bang K = [B]/[A] > 1, nIrd vay phan iing dich chuygn ma.nh sang phai. (chigu thuan, hinh 7.11A). III chat A tinh khigt dgn trang thai can bang, phan ling la ti 51 pilot (AG < 0). Tit do tra di, phan iing la khong tv phat (AG > 0). Gia this chung ta bat dau v6i. chat B tinh khiet thi phan ling cling se dat ten can bang. al ca hai trvang hop, nang Wong tV do Gibbs giam khi phan ling tien trien den gia tri cvc tieu a trang thai can bang. Neu chnng ta bat dau vdi chat A tinh khiet, binh phan ling chfia hau het chat B khi phan ling ket thuc, ta not rang phan ttng theo chieu to A --> B la tii Oat. Thong tit, neu bat dau veil. chat B tinh khiet, phan ling cling ket thlic khi hau het chat B c6 mat. Mac du chi mot lvong rat nh6 chat A tao thanh de thoa man trang thai can bang, ta not rang phan ling nghich tit B —> A la khong tit phat vi no tien trien rat it v6 hitting nay. Doi vdi phan ling tang A B (bat dau vdi tat ca cac thanh phan C1 trang thai chuan), G(B)< G (A) , nen AG°< 0, tvong ling vdi K > 1 va vi vay phan ling tai din bien theo chieu sang phai. Bay gia ta 14i xet phan ling C D, khi K = [D]/[C] < 1 (hinh 7.11B). Neu bat dau vdi chat C tinh khiet, he giai phong nang lilting tit do Gibbs mot cach tit phat den khi dat trang thai can bang. Tuy nhien, tai thin diem nay, phan ling nghich (D --> C) tien trien nhieu hdn v6 phia ngtioc va la tv phat, trong khi phan ling thuan (C —> D) khong tien trien nhieu va la khong tit phat. Vi vay, thuat phcin zing tu' phcit cm cap den mot phcin zing tr(ii &in (chie-m u'u the ho'n) lie phia tao ra sdn pheim, cha khong nhifit thiet phdi li mot phcin zing hoan town. 1 G°< 0 Cant bang h6n hop .G = 0 Nang lu'cing ty' do (G.) Chat A Mgt dO cua phan Crng Chat B Chat C Mac do dm phan Cing Chat D tinh khigt A tinh khigt tinh khigt B tinh khigt Hinh 7.11. Toting quan giCia nang lu'ong tv do Gibbs va mac c10 coa phan Ong. Nang lu'ong to' do Gibbs cela he va mtic'dO phan Ong du'oc minh hop cho hai phan Ling tong quat - co gia tri di' a hang so" K rat khac nhau. d A la phan (mg A B, G °A> G E( , vay K > 1 va AG° < 0. d B là phan Ong C D, G < G D() , vay K < 1 va AG° > 0. Tuy the, 6 c6 hai tru'Ong hop, phan Ong la ty' pilot (AG < 0) mac du 6 cac mCic do khac nhau khi chuyen tit trang thai chugn caa chat cigu ho0c sa'n phgrn vS h6n hop 6 trang thai can bang (AG = 0) 52 2.5. Cac dung cita bi'At thiic tac dung khol l>Idng va hang -s6 can bang 1/ Nhu da biet, can bang the hoa jaicUa cac eau tit trong he phan -tang dan den can bang hod hoc. Vi the, khong gieng nhu dinh luat tec do (phuonk trinh tec do) phai duoc xac dinh bang thuc nghiem, BTTDKL chi di a tren pinking trinh da can bang. Bieu thfic nay la tY) le cac s6 hang nhan vdi nhau, m6i s6 hang duoc luy thita vdi he s6 hop fir& (he se ty Wong) trong pinking trinh phan itng (cac phuong trinh ly thuyet va cac vi du cu the phia tren da minh hoa dieu nay). 2/ Met gia tri K d4c trUng chi c6 nghia khi no lien quan den met pinking trinh Cu the da can bang. Neu cac he se cua pinking trinh da can bang dttoc nhan vdi met thita se; chung thi thita s6 d6 tr6 thanh s6 mu cho BTTDKL va cho hang se can bang di kern vdi no. Chang han, tra lai phan Ung (7-50), neu nhan vdi thita so n, ta c6: n [ aA + bB eE + fF , BTTDKL se la: [E]e [F]t' n Q' = , va K' = (K)" (7-65) [i6i]a[B]b Vi du: (a) N2 (k) + 3H2(k) 2NH3 (k) Kc= 2,4.10-3& 1000°C 7- ( [NH3 ]2 [NH J2 vik: Qc= va. K c= JN2][H2]_ /IA Neu: = 2,4.10-3 JN21[H2]/ L b (a) x —1 3 —2 3 (k) + H2(k) NH33(k) , thl 3 \ 1/3 [NH312 ( [NH312/3 Q'C = JN2 1 [H2 13ibd [N2]1/3[H2 ]ibd [NH]213 va K c= (Kc) 1/3 = = (2,4.10)1/3= 0,13 ■ [N2 ]1/3 [H2 ]ieb Neu tiep tuc, ta c6 the nhan phan Ung (a) veil he se n bat kS7 va tim duoc cac hang se; Kc c6 cac gia tri rat khac nhau [thoat dau c6 cam giac rang, chUng ta da lam thay doi raw do cUa phan itng (the hien qua thay doi gia tri K) chi bang cach thay doi he s6 can bang cila phUong trinh. Cam gide ay that slat khong dung. Bdi vi, nhu da not tren, moi gia tri K gan lien vdi met phan itng cu the. Q va K la nhung dai Wong khue-ch do phu thu(ic vac. Wong chat nen khong the so sanh truc tiep gifia cac phuong trinh khac nhau]. 53 3/ BTTDKL va hang s6 can bang cila phan ling thuan (th) va phan using nghich (ng) có quan he nghich ciao: Q(th) = 1 1 va K(th) = (7-66) Q(ng, K(ng) Chang han, n6i tiep vi du phia tren, phan ling nghich cila (a) dIfOc viet: 2NH3(k) N2 (k) + 3H2 (k) ([N2 1[1-113 1 1 thi KC(ng) = ENH312= 416,7 a 1000°C. Kc 2,4.10 4/ Nhii da thay, Chung ta vie't BTTDKL va BTHSCB ma khOng can biet pinking trinh phan ling bieu thi 1 giai doan phan ling hay 1 phan ling tang gom nhieu giai doan. Bai vi, d TTCB, chi cac he s6tY) hiring moi có vai tra. Neu 1 phan ling la tang cila 2 hay nhieu Phan ling, thi BTTDKL hay BTHSCB se bang tich cac bieu thitc do cila cac giai doan: Qtong= Ql•Q2•C 3• • • Va. Kt6ng= (7-67) VI du: trong &Ong cd cua xe co, t° — 100°C, N2 -yd. 02tao thanh NO, sau do phan ling tiep voi 02tao ra NO2- mot chat 0 nhigni d8c hai. Hai buoc phan Ting la: (1) N2 (k) + 02(k) 2NO (k) K c = 4,3.10-25 (2) 2NO (k) + 02(k) 2NO2(k) Kc2 = 6,4.109 Phan Ling tong: N2 (k) + 202(k) 2NO2 (k) [NO]2 [NO2 ]2= [NO2 ]2 Qcking = Qc(1)*Qc(2) 1/4-1 re\ 1 KTryi nvi- rn LN 2 • L.LN._, _1 2L■--/2J LIN 2J 1.`-'212 KC tiing Kci = (4,3.10-25 ).(6,4.109 ) = 2,8.10-15 5/ Neu cac thanh phan cua phan ling cling pha thi he dat toi TTCB &Ong the. Neu cac thanh phan la khac pha, he dat tai TTCB di the. Trong tniang hop sau, mot hoac nhieu thanh phan ciia he la chat lOng hay chat ran. Chang han, xet can bang khi da voi phan hug' thanh voi sang a — 900°C: CaCO3(r) CaO (r) + CO2(k) [CaO] [CO2 ] theo quy tac viet BTTDKL, ta c6: Qc= . . Tuy nhien, chat [CaCO3 ] ran CaCO3va CaO luon c6 cling nting d8 c3 nhiet d8 cho trueic (cling s6 mol chat 54 trong the tich 1L chat ran). Mat khac, the tich chat ran rat it thay de;i theo nhiet do. V6i. cac IY do do, n6ng do 1 chat ran la hang so. Cling t dng tit dea voi 1 chat lOng tinh khiet. . Vi chung ta chi quan tam den cac ang do thay doi khi phan fing tien den TTCB, nen cac se" hang n6ng do cila chat ran vb. chat 'Ong dnoc lien hop lai trong hang so/chung. Chat ran va long tinh khiet khong c6 mat trong BTTDKL va BTHSCB. Chang han doi v6i phan Ting tren thi: [Ca03] = QC . • = [CO2 ] [CaO] DU hiong CaCO3, CaO di mat la bao nhieu thi BTTDKL cna phan itng cung chi tticing &tong vdi ang do CO2 . 6/ Cho den day, chung ta luen viet cac gia. tri cua Q va K ma khong kern theo don vi, cluing chi la nhUng con so. Dieu nay c6 ngan ge'c tit khdi niem the hod cila 1 mol khi ly tvang. Cdn nhac lai rang, mai so-hang trong BTTDKL (hay BTHSCB) bieu thi tSi le dm luong chat do &toe cila met chat (n6ng do mol/L hoac ap suat) so v6i. Wong chat 6 trang thai chudn dra no (1M hoac 1 atm). • 1,50M Vi du: N6ng do 1,50M tr6 thank = 1,5. Thong tu, ap suat 0,75 1,00M atm tr6 thanh = 0,75. Vi cac se" hang khong don vi, nen theo do Q va K cang khong c6 don Khi bleu thi Wong chat do ducic (Pi, Ci, N) bang hoat de hang so can bang phai dnoc viet la: e f aE • aF K = a b aA 'aB (7-68) aA, aE, aE, aFla hoat do (khong don vi) dra cac chat A, B, E, F tai th6i diem phan ling dat den TTCB. 2.6. Giai quygt nhiYng van de dinh hicing lien quan dgn trang thai can Wang 1/ Xdc dinh hang se' can bang - Neu lnong cac chat d TTCB da biet (nha cac phep phan tich dinh luong), K de clang duoc xac dinh. VI du: Met khei Wong tudng &tong dia hydro va iod duoc-tiem vao binh phan ling 1,50 L o met nhiet do xac dinh. Phan itng sau xay ra: 55 H2 (k) (k) 2HI (k) O TTCB, tim thay trong binh phan Ting có 1,80 mol H2 , 1,80 mol 12vb. 0,520 mol HI. Minh K cua phan ring. Gicii Luang cac chat d TTCB duiic biet theo mol nen phai chuyen ve n6ng d6 mol/L: [H2] = 1,80 mol/1,50 L = 1,20 M. Turing tg, [I2] = 1,20 M va [HI] = 0,347 M. Day la neIng do cac chat a TTCB nen khi thay vao BTTDKL to c6 Kc, va tinh diicic: K [HI]2 0,3472 = = 8,36.10-2 [H2 ][12 ] 1,20.1,20 — Neu mot s6 gia tri a TTCB chua &Toe biet thi phai xac dinh cac gia tri ay tru6c, sau do tim K. Vi du: M6t binh da rut khong khi chiia mot Wang nha b6t graphit (carbon) va duicic nung nOng den 1080 K, sau do them CO2toi alp suat 0,458 atm. Trong he xay ra phan iing tao CO. Khi slat TTCB, ap suat -Using trong binh la 0,757 atm. Tinh K cua phan Gicii Thong thuang giai quyet theo trinh ti sau: + Viet phan iing da can bang: CO2(k) + C (r) 2C0 (k) + Viet BTTDKL TTCB de tim K: ( P2 Qp = co co, Ab = Kp. Cac s6 lieu d'eu cho d dang atm nen K can xac dinh la Kp. C(r) khong c6 mat trong Qp. + Lap bang phan iing (ghi: Wang ban dau dia chat dau va san pham/su Bien dooi cac dai Wang ay/va cac dai Wang a TTCB) bang cach &at x la so atm dm CO2da phan iing (giarn di) a tao san pham. Ap suat P (atm) CO2(k) + C (r) 2C0 (k) Ban dgu 0,458 0 Bien d6i -x +2x 6 TTCB 0,458 - x 2x 56 Giai thich bang: 1 mol CO2phan *rig cho 2 mol CO tao thanh, nen x atm CO2phan iing se cho 2x atm CO tao thanh. Viet -x vi CO2la chat dau se mat di (giam) trong qua trinh phan ling den TTCB; +2x vi CO la san pham. Bie't Pte;ng nen xac dinh duoc x theo dinh lust Dalton [phuong trinh (1-18), chtfong 1]: Prong = 0,757 atm = PCO, PCO (6) = (0,458 atm - x) + 2x x = 0,299 atm. Tii gia tri x tim dtioc, xac dinh ap suat rieng phan. d TTCB: CO, (cID) = 0,458 - x = 0,458 - 0,299 = 0,159 atm PCO (cb) = 2x = 2 x 0,299 = 0,598 atm Thay cac gia tri nay vao Qp tim chicic Kp: Qp = ( D2 \ CO co2 0,5982 = 2,25 = K p 0,159 [Nha hos hoc can cam nhan hay 4 doan duoc ket qua so bO trtioc khi tinh toan theo cac phtiong trinh. Chang han, d day truoc khi tinh Kp, to dti doan: ne'u Kp rat lon thi hau nhu tat ca CO2chuyn thanh CO, nen PuIngse gap doi ap suat ban dau 0,5 atm x 2 1 atm). Ngtioc lai, neu Kp rat nhO, hau nhu khong có CO dutoc tao thanh, nen ap suat cuo'i cung cua he (Prom) gan vOi ap suat ban dau 0,5 atm). B6i vi, ap suat cu6i cling ciia he nam trong khoang cac cuc tri nay (Pto,„gthuc da cho bang 0,759 atm), nen Kptim thay phai có mot gia tri trung gian. Dung nhu ke't qua da tinh, Kp = 2,25, khong qua ldn hay qua be]. 2/ Chuye'n doq gifia Kp va Ke . Vi du: Tinh Kccho phan ling sau: CaCO3(r) CaO (r) + CO2(k) Kp = 2,1.10-4(Ci 1000K) Gicii . Co 1 mol kill ben v6 phai, khong có mol khi nao ben v6 trai, vi vay theo (7-54b): An = 1 - 0 = 1. Tinh Kctheo phuong trinh (7-59): Kp = Kc.(RT)1= Kc= Kp.(RT)-1 Kc= (2,1.10-4).(0,0821 atm.L x 1000K)-' = 2,6.10-6 mol.K 3/ Si dung hang s6 can bang a xac dinh n6ng do — Xac dinh n6ng do cs TTCB tit Ice 57 Vi du: Can bang giiia nitric oxyd, oxy va nitrogen dtioc in6 to bang phtiOng trinh sau: 2NO (k) N2 (k) + 02(k) , Kc= 2,3.103°(6 298K) Trong khi quye'n: P0= 0,209 atm va. PN2 = 0,781 atm. 'Dinh dp suat rieng phan cila NO (met khi dec gay o nhiem mei truCing) TTCB trong khong khi ma con nguai hit th6 hang ngay. Gicii Vi (kilo= 0, nen theo (7-60) thi: PN, • Po 0,781 x 0,209 Kp = Kc= = = 1:1 0 PN20 PNO= 2,7.10-16atm - Xac dinh ang 4 d TTCB tii ang do ban dau va Kc Vi du: Miic 4 bion de'i. CO va H2O thanh CO2va 112chicic sii dung a die'u hoa khi trong hon hop nhien lieu. Neu cho 0,250 mol CO va 0,125 mol H2O vao binh phan ling 125 mL d 900K thi thanh phan caa h6n hop d TTCB la bao nhieu? Bie't Kc= 1,56. Gicii Phan ling da can bang la: CO (k) + H2O (k) CO2(k) + H2 (k) BTTDKL: Q c= [CO2 ] [H2 ] [CO] [H2 0] Tinh ang do ban dau cim cac chat dau: 0,250 mol [CO] - = 0,125 L 2,00 M 0,125 mol [1120] = - 1,00 M 0,125 L Lap bang phan ling: dat x = ang dO da phan fing N6ng do (M) CO (k) + H2O (k) CO2(k) + H2 (k) Ban d6u 2,00 1,00 0 0 Bi6n d6i -x -x +x +x 6 TTCB 2,00 - x 1,00 - x x x 58 Thay cac gia tri a TTCB vao Qcd6 có Kcda bi6t: Kc [CO2 ] [F12 ] x . x x2 = • = 1,56 [CO] [H2 0] (2,00 - x). (1,00 - x) x 2- 3,00x + 2,00 Sap x6p lai, thu doe clang phuong trinh bac 2: 0,56x2- 4,68x + 3,12 = 0 Giai plutong trinh nay, &toe x = 7,60 M va x = 0,73 M. Gia tri x = 7,60 M khong coy nghia hod hoc vi no lon hdn nOng d6 ban dau. Vi vay, x = 0,73 M, va tinh: [CO]C, = 2,00 M - x = 2,00 M - 0,73 M = 1,27 M [112 0],b = 1,00 M - x = 0,27 M [CO2]th = [112],b = X = 0,73 M Kim tra lai xem cac gia tri vita tim citiOc có cho Kcnhti da bie't hay 0,73 x khong: K 0,73 = 1,6; ke't qua dUng vi 1,6 la trong pham vi lam 1,27 x 0,27 trOn dm 1,56. 4/ Xac dinh chi6u huong cua phan ling va tinh ang dO d TTCB. Khi chi cho bie't Wong cac chat dau thi &tong nhien phan ling phai ti6n trign ve phia san pham va trong bang phan fing ta dat dau am (-x) cho sit bie'n ct6i cac chat dau. N6u ta bat dau vii mot hen hop bat kY g6m chat dau va san pham thi chidu hiking phan ling se chita re rang. Khi ay, bat bu6c phai so sanh Q va K de xac dinh xem phan itng "trei" theo httdng nao vg TTCB. Digu nay se cho bi6t, ta can crat x mang dau am hay dau diking trong bang phan fing. Vi du: Hai thanh phan cUa khi tii nhien (CH4va H2S) can duoc nghien ciiu de tao ra cac san pham (CS2va H2) dila theo phan ling: CH4(k) + 2H2S (k) CS2(k) + 4H2(k) Trong mot thi nghiem, cho 1,00 mol CH4; 1,00 mol CS2; 2,00 mol H2S va 2,00 mol H2 chtoc trOsn 'An trong binh 250 mL a 960°C. nhiet de nay, phan itng có Kc= 0,036. a) Phan ling se tie'n tri6n theo huong nao dd dat TTCB. b) Bang pile') phan tich, ngtiai ta tim thay [H2] = 1,76 M cJ TTCB. Vay, n6ng de cita cac chat khac la bao nhieu? 59 Gidi a) Tinh nOng d6 ban dau: 1,00 mol [CH4] = - 4,00 M 0,250 L TUong tit, [H2S] = 8,00 M; [CS2] = 4,00 M va [H2] = 8,00 M. Tinh BTTDKL: [CS2 ] [H2]4 4,00 x 8,004_ Q c 64,0 [CI-14 ] [H2S]2 4,00 x 8,002 So sanh Qcva Kc: Qc> Kc (64,0 > 0,036). Vi vay, phan itng tien trien v6 ben trai (chieu nghich), ang d6 chat dau se tang va san pham se giam. b) Lap bang phan itng vesi x = [CS2] da giarn do phan itng (ghi -x) hay [CH4] duoc tao thanh (ghi +x). Nong dO M CH4(k) + 2H2S (k) CS2 (k) + 4H2(k) Ban dau 4,00 8,00 4,00 8,00 Bien d6i +x +2x -x -4x 6 TTCB 4,00 + x 8,00 +2x 4,00 - x 8,00 - 4x Tinh x: WO [H2], = 1,76 = 8,00 - 4x = x = 1,56 M [CS2],b= 4,00 - x = 4,00 - 1,56 = 2,44 M [CH4]Cb = 4,00 + x = 4,00 + 1,56 = 5,56 M [H,S],b= 8,00 + 2x = 8,00 + 2 x 1,56 = 11,12 M Kim tra gia tri Kctit cac gia tri vita tim dtioc: Kr= 2'44 x 1'764 = 0,0341 0,036 - 5,56 x 11,122 5/ Si dung gia thiet de don giAn hoa. phep tinh Trong nhieu tniCing hop, can cii vao dau hieu hoa hoc, to c6 the data them gia thiet nham tranh phai giai ph Icing trinh bac 2 hoac bac cao hon. N6i chung, neu phan itng c6 hang s6 can bang kha nhO (thtfOng << 1) va ang do cac chat dau lai kha 1.6n thi su Wen d6i n6ng d6 v6 TTCB c6 the 136 qua ma khong tao ra mot sai s6 clang ke: 60 [chat ddu]bd x [chat d'au]bd"=-,' [chat ddukb Gia thiet nay khong c6 nghia la x = 0, vi nhti the thi kh8ng c6 phan Ung. Tieu chuan 6 day la: net' gia thiet gay ra sai s6 :5_ 5% thi dtfoc coi la dung va goi Cat la thoa man gia thiet 5% (nhung nghien citu yeu cau chinh xac cao có the dat gia thiet khac nha hdn 5%). VI du: Phosgen la 1 chat d8c chien tranh (cla bi cam theo Hiep U6c Geneva) phan huV bai phan ing: COC12(k) CO (k) + Cl2(k) Kc= 8,3.104(Cr 360°C) Mall [CO], [C12] va [COC12] khi nhiing Wong sau day cua phosgen phan 1Vva dat den TTCB trong binh 10,0 L: a) 5,00 mol COC12 . b) 0,100 mol COC12 . Gicii a) BTTDKL: Qc [CO] [C1 2 ] [COC12 tinh [C0C12]bd = 5,00 mol/10,0 L = 0,500 M Lap bang phan itng voi x = [COC12] da phan Nong dO M COC12(k) CO (k) + Cl2(k) Ban dgu 0,500 0 0 Bign d6i -x +x +x a TTCB 0,500 - x x x Q c = [co] [C12] X . X [COC12 cb 0,500 - x = Kc= 8,3.104 Vi K nha, phan itng khong tien trien manh sang phai, nen gia thiet 2 x << 0,500 M = 0,500 - x 0,500 M, theo do = 8,3.10-4 0,500 = 2,0.10 2 . 2,0.10-2 Kim tra gia thiet: x 100 = 4% , nha hon 5%. VI vay, gia thiet 0,500 thing (hay thoa man gia thiet 5%). 61 Tinh [CO]c, = [C12]6= x = 2,0.10-2 M [C0C12L, = 0,500 - x = 0,480 M b) Doi yeti truang hop 0,100 mol COC12. Tinh Wong tu, voi [COC12]bd 0,100 mol/10,0 L = 0,0100M. Theo do, d TTCB to c6: Q C = r[C0][C12 ] = x2 = K = 8,3.10-4 [COC12 ch0,0100-x c N6u gia thie't 0,0100 M - x 0,0100 M va X2 0,0100 = 8,3.10-4 = x = 2,9.10' 2,9.10-3 Kim tra gia thi6t 5%: x 100 = 29% > 5%, vay gia thi6t sai. 0,0100 Phai giai pinking trinh bdc 2: x2+ 8,3.10-4X - 8,3.10-6= 0 , tim dtiOc 1 gid tri c6 nghia: x = 2,5.10-3M, va xac dinh: [CO]c , = [Cid = 2,5.10' M [C0C12]cb = 1,00.10-2 M - x = 7,5.10-3M 6/ Lim y chung: + Bang phan iing la mot ky thudt c6 ich, ngdn gon ma toan canh, tranh dtioc nham ran, nhat la d6i viii nhiing bai toan c6 nhi6u dii lieu thuic nghiem. + Cac bai giai dinh Wong cua muc 2.6, phia tren cua cac muc trU6c niia hoac cua muc con-ti6p sau la nhiing truang hop th.thng gdp trong thiic hanh hay nghien diu hod hoc, trong san xudt va ca trong tut nhien. Can chit Y each vi61 cac chit so c6 nghia (xem Phu luc cuoi Quy6n nay) duoc th6 hien trong cac vi du da cho. 2.7. Sly dich chuye'n can bang. Nguyen 1Y Le Chatelier D'a'.c diem clang lieu y nhgt cua mot he can bang la kha nang chuy6n dich sang mot trang thai can bang moi khi cac di6u kien thay doi. Chi6u hilOng chuy6n dich dia can bang duoc chi ra trong nguyen 157 Le Chatelier (nha Hod hoc Phap 1850 - 1936). Khi thay doi mot trong s6 cac thong s6 xac dinh trang thai can bang dia mot he thi can bang se chuyk dich theo chik cheing1ai. su thay doi do. 62 D6i vOi can bang hod hoc thuong xay ra 3 su thay d6i: thay d6i ve n6ng do chat dau hay san pham, thay d6i vg ap suat hay the tich c-Cia he, va thay d6i ve nhiet do. Diia vao nguyen lY Le Chatelier, chUng to se thay re rang hdn nhung ski thay doi ay anh huang nhu the nao den trang thai can bang. I 1 Anh hu'Owg czta sa' thay dai nong coo den, can bing hoci hoc. Xet can bang sau duoc thiet lap 523K: PC13(k) + Cl2(k) PC15(k) Qc= [PC15] = Kc= 24,0 [PC13 ] [Cl, ] Vi Kcchi phu thu6c vao nhiet do nen 6 T = const (= 523K): + Neu tang n6ng do PC13ho4c Cl2(cac chat dau) thi can bang se chuyen dich sang phai tao ra them PC15(san pham) de giii Kc= const. + Ly luan Wong tu de ket luan rang, can bang se chuyen dich sang trai (tao them chat &du) neu rut best n6ng dO PC13hoa'c C12khOi he, hay tang them n6ng do PC15vao he. NMI vay, neu tang n6ng 110 cua mot thanh phan, he can bang se chuyen dich theo chieu tieu thu bot thanh phan do. Neu giam n6ng de) cila mot thanh phan, he se chuyen dich theo chieu tao them thanh phan do. He can bang hien chuyen dich theo chieu thong lai sli thay cloi n6ng do. Tuy nhien, khong loai trif dUcic hoan toan sti thay doi do. Chang. han vai vi du dang xet, TTCB ban dau dtioc xac lap b6i cac n6ng de sau: [PC13] = 0,200 M; [02] = 0,125 M; va [PC1,] = 0,600 M, vi the: [PC15 ] 0,600 KC (TCB ban clAu) = T 24,0 [PC13J [C12 ] 0,200 x 0,125 Neu them 0,075 M C12, can bang se chuyen dich sang phai de tieu thu (lam giam) n6ng do C12, tang them [PC15], va met TTCB moi duoc thiet lap. Thiic nghiem cho biet, i TTCB men [PC15] = 0,637 M; [C12] = 0,163 M va [PC13] = 0,163 M, nen: KC (TTCB moi) = 0,637 = 24,0 0,163x 0,163 Gia tri Kckhong thay d6i, nhiing [C12] them vao (0,075 M) ding chi tieu thu diidc: 63 [Cid tieu thu = ([C121TTCB ban dau 1C1.21 them vac)) EC121TTCB mdi = (0,125 M + 0,075 M) - 0,163 M = 0,037 M (< 0,075 M), nghia la kh6ng loai trii dUoc hoan toan n6ng d6 C12mdi them vao. 2/ Anh hu'Ong cua sr.! thay c of ap suat den, can bang hoci hoc. Khi xem xet anh Inaing cua ap suat den TTCB, to chi quan tam den nhting he c6 mot hay nhieu thb.nh phan la khi. Chat lOng va ran gdn khong chiu nen, vi vay thay doi ap suat it c6 anh twang. Ap suat chi thay d6i khi thay d6i n6ng do cUa thanh phan khi; them 1 khi trd (khi khong tham gia vao phan ling) va thay d6i the tich binh phan ling. TrUong hop anh In.fang do thay d6i n6ng d6 cua mot thanh phan cila he da dude xet phia tren. TrUang hdp thay do' ap suat bang cach them mot khi tri vao he thi khong anh hu6ng den vi tri can bang. Bai vi, the tich khong thay d6i nen tat ca n6ng d6 chat dau va san pham d TTCB van nguyen. Mac du ap suat tong tang, n6ng d6 phan mol giam, nhung -CY le ap suat rieng phan cua san pham va chat dau van nhu triloc nen vi tri can bang khong thay d6i. Truang hdp thay doi ap sudt do thay doi the' tich thu'eing anh hu'O'ng reit nhi& tdi vi tri can bang, vi thay d6i the tich clan tdi ski thay de;i n6ng d6 (la s6 mol khi tren 1 L the tich cua binh chfia): sti giam th4 tich binh chiia lam tang n6ng d6 va su tang the tich binh chiia lam giam n6ng d6. Theo phucing trinh (7-59): KP KN (Puind cAbn thi ap suat khong anh ht ang den Kp, nen: + Neu An > 0, khi tang P KN phai giam, nghia là can bang bi chuyen dich sang trai (phia it mol khi hdn) de ch6ng lai sti tang ap suat. Nguoc lai, khi giam P, can bang se chuyen dich sang phai. + Neu An < 0, khi P tang KN phai tang, nghia la can bang bi chuyen dich sang phai (phia it mol khi hon) de lam giam su tang ap suat. Nguoc lai, khi giam P, can bang se chuyen dich sang trai. Neu An = 0, ap suat khong lam chuyen dich can b.'ng. Tom lai, neti he can bang c6 sit chenh lech s6 mol khi gifia cac chat dau va san pham thi: khi tang ap suat, can bang chuyen dich vd phia c6 s6 mol khi 64 It hdn; khi giam ap suit, can bang chuyen dich ye phia có s6 mol khi nhieu hon. Dieu nay phit hop vdi nguyen VT Le Chatelier: he can bang hien chuyen dich theo chieu thong lai sit thay de2i dp suit. 31 Anh hu'Ceng caa sa' thay ctdi nhi0 coo sten can bcing hod hoc Trong 3 stl thay d6i, chi co nhiet do lam thay d6i hang so can bang K. Tit phtiong trinh (6-60): dG = VdP - SdT , khi P = const thi: \.„ aT p _-s (a(Aw aG \ aT )p (7-69) Thay (7-69) vao (6-52), thu dtioc: AG = AH + T a(AG) aT 2 p Chuyen ye (7-70) va chia 2 ye cho T2, to co: T(a(Aw _ AG aT p AH T2 T2 Ve trai ciia (7-71) có clang tong thlic co ban cila vi phan (7-71) trO thanh: a ( AG \ AH aT, p T2 (7-70) (7-71) VdU - UdV v2 , nen (7-72) Cac pinking trinh (7-70) va (7-72) là nhiTing clang khac nhau cua phudng trinh Gibbs - Helmholtz. Xet d trang thai can bang va thay (7-72) vao (7-51), thu duoc: AH" aT p0 RT2 (7-73) Day la phtiong trinh ding dp Van't Hoff, theo do: Neu phan ling la thu nhiet, AH()> 0, thl khi T tang K1 se tang (deng bien). Dieu nay có nghia là khi tang nhiet de, can bang chuygn dich sang phai tao ra nhigu san phm hon (co the xem nhiet la met thanh phan cua cac chat dau, nen khi tang no, can bang chuyen theo chieu giam no, tilt là sang phai). 65 Neu phan ling la toa nhiet, OH()< 0, thi khi T tang, Kp se giam (nghich bien), can bang chuyen dich sang trai (6 day, xem nhiet la mat san pham, nen khi tang no, can bang chuyen theo chieu tao ra nhieu chat ddu hon, tiic là chieu nghich). Trong khoang hep cila nhiet do tit T1den T2, xem AS° va. AH° khong d6i thi phuong trinh (7-73) trii thanh: T2 0T, 0 1 1 - fdlnK p= T 2= AH 1 AH fdT K in (7-74) T R JT ,T2 KT, R. TI T2 j Xet plutang trinh Van't Hoff (7-74), ta de dang rut ra ket luan gi6ng nhii tren. Mat khac, neu biet gia tri hang s6 can bang KTa nhiet 4 T1va hieu iing nhiet cua phan ling (thuang dung dU lieu d di6u kien chuan T = 298 K), ngiidi ta c6 the xac Binh KT, d nhiet do T2nao do. Ngitac 10, khi biet gia tri cac hang s6 can bang d 2 nhiet do khac nhau, ta c6 the tInh dtiac AH° cita phan ling (chu khi AR' tinh bang Jun, thi R = 8,314 J.mo1-1.1C-1). Tom lai, anh huang cua nhiet do den he can bang tuan theo nguyen lY Le Chatelier: chieu chuyen dich can bang la chi& chdng lai su' thay ddi nhi0 4/ Su thie-u yang anh hu'a* caa chdt xac tac. O muc 1.7 phia tren ta da biet chat xtic tac lam tang t6c do phan ling do lam giam nang Kiang hoat hod, vi vay lam tang phan iing thuan va phan itng nghich voi ding mite do. Theo do, chat )(tic tac khong lam thay de>i vi tri can bang. Tuy nhien, ta se thay ngay la chat )(de tac gift vai tr6 chit ch6t de t6i ttu hod v6 nang Wang va thai gian cho mat he phan 5/ Ong dung thu'c to cac nguyen tac chuyen dich can bang. Nitrogen c6 mat trong nhieu hap chat tit nhien va tang hap. Ngu6n nitrogen giau nhat trong til nhien la khi quyen, yeti 4 trong 5 phan tit la N2 . Du vay, nguein cung cap nitrogen c6 the sit dung dtiac trong sinh hoc va san xuat bi han the bdi hoat tinh hoa hoc cita N2rat thap. D6 la ket qua cita lien ket bai manh gan cac nguyen tit N vdi nhau, nen nguyen tit N rat kh6 gan vdi cac nguyen tit khac. Si gan ket N duac thuc hien nha hoat tInh cita mat s6 enzym tim day trong vikhua.'n hoac nha nhiet do rat cao tai tia Em dien cac anh chop. Ngay nay, gan 13% su c6 dinh nitrogen tren trai d'at &talc tintc hien trong cong nghiep nha chu trinh Haber (Fritz Haber, nha hoa hoc Disc, 1868 - 1934) v6 the tao amoniac tif nguyen to 66 N2 (k) + 3H2(k) 2NH3(k) Aii(p)t, = -91,8 kJ [Hang nam, 110 trileu tan NH3dtioc san xuit theo chu trinh nay. Tinh tren don vi mol thi amoniac dtioc dig tao nhigu hdn bit ky hop chit nao khac. Hon 80% san Wong NH3clUng lam phan bOn (ngn nong nghiep tien tign sii dung phan bon clang NH3long duoc nen va phun truc tiep vao trong dit). Cdc ling dung khac ciia NH3g6m: san xuit chit no, HNO3, nylon, nhigu loai polymer; lam chit on Binh cao su, chat lam lanh, chit lam sach; trong tang hop cac chit lulu co va duoc phim]. Chu trinh Haber la vi du dien hinh v6 dp dung nguy8n lY chuygn dich can bang. Xem xet phan iing d TTCB, to thiy có 3 cach de dat t6i da san Wong . NH3: - Gidm [NH3] bang cach lien tuc rut NH3khi he phan ling de can bang luon chuygn sang phai tao ra san phdrn (NH3). - Tang cip suit cac khi la chit diu (N2, H2) de can bang chuygn dich manh vg phla tao s6 mol khi it hdn - phla tao san phA:m (NH3). - Gidm nhiet dO. Vi chigu phan fing tao thanh NH3la toa nhiet, nen khi giam nhiet can bang se chuygn dich theo chigu do. Tillie t6 san xugt can teci Liu ca, san Wong va t6c dO. nhiet do thip, san Wong cao nhung t6c dO lai cham. Vi the, cac nha may san xuit amoniac hien dai boat dong d ap suit - 200-300 atm;'nhiet dO khoang 673 K (400°C), chit xuc tic g6m cac khoanh sat tinh thg 5-10 mm dtioc nIrang chim trong h(in hop nOng chay cua MgO, A1203va SiO2. H8n hop khi (cac chit din) duoc nen lai (N2/H2 = 1/3 theo thg tich) va tiem vao bung phan fing nhiet do va dp suit cao. Khi hiSn hop chay qua )(tic tic, mot phin hiOng nhiet ma phan iing toa ra duoc cung cap de nang cao nhiet dO cua bung phan fing. Hon hop can bang tao thanh hic nay chlia khoang 35% the tich NH3duoc lam lanh dgn ngung to NH3clang ran (tI\TH3= -33,4°C) va duoc rut ra. Vi digm soi cila N2 (-196°C), cila H2 (-253°C) thip hon rat nhigu nen chUng van a dang khi va duoc bcim trei lai bung phan iing de tigp tuc chu trinh. 2.8. Can bang trong chuygn hoa to bao T6 bac) sinh hoc la hinh anh vi mo kY la Cila ski bign d6i va can bang hod hoc. Ttif nhiing vi khudn don gian nhit cho tdi nhfing day thin kinh dac biet nhit, m6i t6 bao dgu thkic hien hang ngan phan iing dg nu& &tong va bai tigt, phat trien va sinh san, di truye'n va trao d6i. Tit ca cac phan ling nay tao 67 thanh sti chuyen hod cilia to bao. Day la vo s6 kST tong cilia sit be gay li8n ket, tang hOp sinh •hod hoc va chuyen do2i nang Wong chide to chfic thanh chu6i phan itng goi la con &tong chuyen hod. Mot s6 con ditOng hien d6i cac polymer sinh hoc trong thiic an thanh nhcing monomer cho xay dung nen tang co the: &tang, amino acid, nucleotid... Mot s6 con &tang sit dung nhiing phan tit nhe nay de tao nang Wong, va sau do lai sit dung rat nhieu nang Wong de tao thanh cac phan tit có chitc nang khac: hormon, chat dan truyen than kinh, cac phan tit khang the va cac biopolymer cua chinh to bao. Ve nguyen tic, moi buoc trong con ditOng chuyen hod la mot phan iing thuan nghich duoc xuc tac bdi mot enzym dac biet (xem xuc tac enzym, muc 1.7 phia tren). Tuy nhi8n, ta se thay, mac du có nhcing nguyen VT can bang nhu da thao luan teen, TTCB khong bao gia dat duoc trong nhfing con &tang do. \Ted mot chu6i phan ling gem nhieu giai doan, san pham cua phan ling this nhat la chat dau cua phan Ting this 2, san pham cua phan iing this 2 la chat dau cua phan ling this 3... va cit the. Chang han, xet con &tang g6m 5 budc chuyen threomin (1 amino acid phan cue, chila nhom OH) thanh isoleucin (1 amino acid khong phan cuc, mach thang) nhu sau: Enzym I (Threomin dehydratase) Enzym 2 Enzym 3 Enzym 4 Enzym 5 Ketomethyl valerat Dihydroxy methyl valerat Threomin Acetohydroxy- lsoleucin butyrat Ketobutyrat uc the Threomin duoc cung cap tit mot viing khdc cua t6 bao, tao thanh ketobutyrat nha xfic tac cua enzym 1 (phan ling 1). Vi tri phan ling 1 lien tuc chuyen sang phai bai vi ketobutyrat lien tuc duoc rut vao lam chat dau cho phan ling 2. Tufting tu, phan ling 2 chuyen sang phai vi san ph6m cua no la chat dau cho phan ling 3. 1\46i phan ling ti6p theo deu lam dich chuyen vi tri can bang ciia phan ling tritdc ve huong tao ra san pham. Su chuyen dich can bang lien tuc tao ra 2 dac diem chinh cua cac con &tang chuyen hod. This n1-4t, moi phan iing deu tien trien vdi gan 100% san luting. Nghia la, hau nhit tat ca cac phan tit threomin di vao 1 \Tung cua to bao deu chuyen thanh ketobutyrat, moi phan tit ketobutyrat lai tao thanh cac phan tit khac va cut nhu vay. This hai la, nting cti5 chat dau va san pham gift gan nhur khong de;i, mac du h8 khOng bao gia dat TTCB. Day goi là trang thai On dinh, v6 co ban la khac voi nhiang gi chUng ta da thao luan d phla tren. Trong cac h8 can bang, t6c dO phan ling cua cac huong bang nhau dan den ang do khong d6i. Con trong cac 118 on dinh, t6c dO phan iing ve mot hudng dan den ang dO khong d6i (gi6ng flint thiet lap trang thai on dinh trong 6ng nuoc, bang cach dieu chinh de Wong nit& di vao bang Wong nit& di ra). 68 Dieu quan trong la to bao dieu hoa n6ng dO cua san pham cuai cling cUa con dudng. Nhd lai rang, mot enzym xfic tac phan itng khi cd chat xam nhap vao vi tri hoat Ong. Tuy nhien, n6ng dO cd chat rat Ion so vdi n6ng d6 enzym, nen neu .khong có yeu to diet' hoa, tat ca cac phan itng trong to bao se xay ra vdi tac dO tai da. lJoi veil day chuyen san xuAt cong nghiep thi day IA dieu 13-7 tUdng, vai mot sinh vat do lai la mot tham hoa. De diet' hoa tat ca cac san pham tao thanh, tac dO mat s6 giai doan chU chat duoc kiem soat b6i cac enzym dieu hoa, 6 chnng, ngoai vi tri hoat &Ong thi con chlia mot vi tri itc che tren be mat. Cau true khong gian 3 chieu cUa enzym lam cho khi vi tri fic die bi xam chiern thi hinh dang ciia vi tri boat dOng bi thay doi va phan ling khong con duoc xuc tac nua. Vi du don gian nhat ve kiem soat chuyen hod la san pham cuai cling ci'm con &tong &mg vai tr.() phan tit lac ch6, con enzym dieu hoa IA enzym xtic tac buoc dau tien. Chng han, khi to bA.o tam thdi khong san xuAt protein thi isoleucin dude tang hop b6i con &tang nay khong dude rut di. Khi n6ng dO dm no tang len thi isoleucin se chiem vi tri fic che cua enzym 1 va "dong ngay con during san xugt no mot cach hau hieu. Qua trinh do goi là dieu hoa ngudc bang san pham cUa phan itng cuai Nhieu con &long diet' hoa plific tap hdn theo nhung mo hinh khac nhau, nhung rat nhieu trong s6 do van la cd che dieing tit dieu hoa nguoc. Nhu vay, std dieu hoa cac con &tang chuyen hod lai bat ngu6n Ulf cac nguyen 1ST cila thing hoc va chuyen dich TTCB. 69 ChiIdng 8 ski HINH THANH VA CAC TiNH CHAT CCJA DUNG DICH MUC TIEU 1. Neu ctinh nghia va each phan loai cac dung dich, ccic ndng do. 2. Gidi thich cac thong tin ye trong thcii ci a mot chat nguyen chat dilac ghi tren gidn dd pha. 3. Trinh bay cac nguyen nha n ve lien k et va nhiet dOng hod hoc trong qua trinh hoa tan hinh thanh dung dich. 4. Van dung du'ac dinh luat phan bd, ctinh luat Henry, cac dinh luat Raoult va Van't Hoff cho cac loai dung dich de giai thich va giai quyet nhting van ctj tic thvc te: 1. NHUNG VAN DE CHUNG VtsSU HINH THANH DUNG DICH 1.1. Dinh nghia - Phan loai Cac h" phan tan: mot chat phan tan thanh nhiling hat rat nhO vao trong mot chat khac lam thanh mot he phan tan. CO tat ca 9 he phan tan (bang 8.1). Bang 8.1. Cac h0 phan tan He phan tan Vi du 1. K/K (kill ph5n tan trong khi) KhOng kW 2. L/K (lOng ph5n tan trong khi) Suring mu 3. R/K (ran ph5n tan trong khi) Hai iod thang hoa; bui; khoi trong khOng khi 4. K/L (khi ph5n tan trong king) Nutic thien nhien hoatan oxy; nuOc uong có gas (CO2) 5. L/L (I6ng ph5n tan trong !Ong) C6n trong nude; nhili Wang 6. R/L (ran ph5n tan trong king) Cac mu6i, during hoa tan trong nuac; huy6n phi; keo 7. K/R (khi ph5n tan trong ran) Hydro bi hap phu trong platin 8. L/R (long ph5n tan trong ran) Hai nutic bi hap phu trong than hoat, silicagel 9. R/R (ran ph5n tan trong ran) Cac hop kim; khoang chat; thug tinh mau; men sit; ceramic 70 Theo nghia rang, ngtioi ta goi tat ca cac he phan tan nInt th6 la dung dich; chat phan tan thank nhang hat rat nhO (phan tit, ion, hoac mot tap hop cua chnng) goi la chat tan; moi truang phan tan goi la dung moi. Vay„ dung dich g6m chat tan va dung moi. Ngttai ta thtiOng quy Binh dung mei la eau al ma 6 clang tinh khik no c6 trang thai tap hop giong nhii dung dich (vi du, dung dich nttdc cua cac mu6i, thi di nhien nti6c la dung moi). N6u ca hai cau tit (chat tan va dung moi) c6 trang thai tap hop nhti nhau (vi du, rtiOu Ira mi6c), thi dung moi la cau tit c6 Wong lon hon. - Thong thtiOng ngtfoi ta goi dung dich lot mot he phan tan ma dung moi la mot chat l6ng. Dung dich 'Ong la he phan tan ph6 bi6n va quan trong nh'at trong to nhien va trong sinh quyen. Gido trinh nay cling chi nghien cuu ki6u dung dich nhti the. Dung dich ma dung moi la chat 16ng lai dtioc chia thanh 3 loai tuST theo kich tint& cua ti6u phan (hat) chat tan. Bang 8.2 trinh bay sti phan loai Ira dac tinh cac dung dich lOng. Bang 8.2. Ph5n loai cac dung dich long du'a tren kich thu'dc tau phan chat tan Kich Loai • Dung dich th5t, Om: thu'dc ch'it tan Dac tinh dung dich Vi du cac chat tan Chat tan kh6ng nhin thay - Dung dich cac chat kh6ng dian ly (dung dich ph5n ti1'). - Dung dich cac chat dian ly. • Dung dich keo • H6n dich, g6m: - NH Wong (nhil dich), ha L/L - Huyen phO, he R/L < 1 nm 1+100 nm > 100 nm du'oc trong kinh hign vi dian 0; di qua du'oc cac mang sieu loc va mang ban tham; khugch tan nhanh. Chat tan khOng thay du'oc trong kinh hign vi thuting, nhu'ng c6 the phat hien trong kinh slat,' hign vi, thay du'oc trong kinh hign vi dian tif; lot qua giay loc thu'Ong, n1-fling kh6ng qua du'oc mang ban tham; khugch tan rat ch5m. Chat tan nhin thay dutic trong cac loai kinh hign vi; kh6ng qua du'oc gray loc thu'ong, kh6ng tham tich qua mang ban tham; kh6ng khugch tan . Cac ph5n to' oxy, glucose; cac ion don giAn Keo bac clorid (AgCl)n ; polymer thien nhien ho5c tang hop Cac hat khoana' phu sa; cac nht? tu'ong va huyen phu du'oc dung; cac to bao hong cau trong mai Sit phan loai dung dich (he phan tan lOng) theo nhfing gioi han kich thiloc cua ti6u phan chat tan (chat phan tan) chi la Wong deci. Cac dai phan tit nhit cac polysaccharid, cac protein va cac polymer a kich tint& du lon, co th6 vita tao ra dung dich phan tit (dung dich that), vita tao dung dich keo. MOt vai nha Wong hoac huy6n phu chlia cling loai hat phan tan c6 kich tint& nhO hdn 71 met cluit thi dude xep vao dung dich keo, con lon hon met chat lai dude phan loai la h6n dich. Nhfing dung dich chiia chat tan tinh khiet &toe dieu the trong phOng Ulf nghiem hoac trong cong nghe dfing cho muc dich nghien an' hoac lam thuo-c. Dung dich trong thien nhien, da. c biet trong cac mOi truang sinh hoc, deu la nhUng dung dich plific tap. Vi du, scia Tang vat la met dung dich phlic tap, go'm 87 - 89% nuoc (dung moi); 2,7 - 4,5% lipid (a dang nhu tdong, to tach thanh yang sila dung lam bo); 2,7 - 3,8% casein (la protid dang dung dich keo, c6 the tach rieng lam ph6 mat) va 4,5 - 4,7% lactose (duang sfia) cling voi cac muOi khoang, cac vitamin dang dung dich that). Mau nguai la met vi du khac v6 mot he phan tan bao gOm ca. 3 loai dung dich long dien hinh va rat plific tap. Hang cau, bath cau, tiL cau la nhiing to bao mau, chiem 40 - 46% the tich mau, tao thanh he phan tan th6 (116n dich) trong - huyet tticing. Huy& ttidng chiem 54 - 60% the tich mau (chi yeu la nude chiem 90% khoi ludng huyet ttiOng, &mg vai tr.() dung m8i) vita là dung dich keo (vi chiia cac dai phan tit nhti cac albumin; protein; plific hop protein - lipid), vifa la dung dich that (vi chiia cac chat hoa tan la nhiing phan ti nhO: oxy; glucose; cac hormon, enzym; cac chat vo cd Nat, IC, Ca', Mg', Cr, HC032-, phosphat, sat, dOng, cobalt, selen...; cac chat can ba do to bac) dao thai ra nhu CO2, ure, creatinin, cac acid va sac to mat...). Nhcing kien thfic trinh bay trong gido trinh nay chi' yeu la cho dung dich that, goi chung la dung dich. He phan tan keo dude de cap ci chuyen de rieng. 1.2. Cac each bie'u thi nong do Bang 8.3. Cac loai nong de) Loai nong do Ky hieu Dinh nghia + Phan tram theo kh6i litong (KL) + Phan nghin theo kh6i ludng + Phan tram theo thg tich (V) + Phan tram theo kh6i lu'ong-the tich + Phan nghin theo kh6i ludng-thg tich + Mol + Du'ong bong + Molan + Phan mol 72 % (KL/KL) %o (KL/KL) % (V/V) % (KLN) %o (KL/V) hoac g/L M, mol/L N m X hoac NI; S6 g chat tan trong. 100 g dung dich SO g chat tan trong 1000 g dung dich SO mL chat tan trong 100 mL dung dich S6 g (hoac s6 mg) chat tan trong 100 mL dung dich SO g chat tan trong 1000 mL (= 1 L) dung dich SO mol chat tan trong 1 L dung dich S6 dudng Iu'ong gam chat tan trong 1 L dung dich S6 mol chat tan trong 1000 g (= 1 kg) dung m6i Ti so giira s6 mol mot chat trong dung dich va tong so mol cac chat co trong dung dich (ngu tinh ra % thi goi la phan tram mol) N6rg d6 la cach bieu thi thanh phan dinh luong cua mot dung dich. NO có the bieu thi Wong chat tan trong mot the tich xac dinh cila dung dich hoac luring chat tan trong mot khoi hldng xac dinh cila dung dich hoac cUa dung moi. Lacing chat tan trong dung dich cang lOn thi n6ng d6 cang lon va nglioc lai. Bang 8.3 tom tat cac loai nang do thliang dtioc dung trong hod. hoc va Y- Duoc. DO% day.là mat s6 vi du cu the v6 cac loai nang d6 hay gap. - N6ng d6 %, %o theo kh6i luong/khOi Wong: Vi du: Dung dich KNO310% c6 nghia la có 10 g KNO3trong 100 g dung dich. Dung dich cac acid dac H2SO4, HNO3va HC1 ban tren thi truang c6 nang d6 Wong ling bang 96%, 65% yd. 36%. BOi vi, do the tich dung dich de dang hdn do kh6i Wong, nen ngithi to thifang ghi kh6i. Wong rieng kem theo cho loai dung dich nay, de chuyen d6i to khol hldng chat can lay sang the tich dung dich can dong. Vi du, HC1 36% có D = 1,179 g/mL (6 20°C). Dung dich NaC1 9%o c6 nghia la có 9 g NaCl trong 1000 g dung dich. - N6ng d6 %, %o theo khol. Itiong/the tich (thithing duoc viet g/100 mL; g/L...): Vi du: Dung dich glycerin 10 g/100 mL, glucose 50 g/L có nghia la co 10 g glycerin trong 100 mL dung dich, có 50 g glucose trong 1 lit dung dich cho 2 dung dich hiring Ting da ke. - N6ng do mol/L (M): Mol la mot Wong chat chlia s6 hat ding kieu cau trilc (phan tii, nguyen ti ion, electron, proton...) bang s6 Avogadro 6,022.1013. ThUang sii dung la mol/L, s6 phan tii gam/L. Cac, dung dich c6 nang d6 mol bang nhau thi chiia ding s6 Wong hat chat tan trong nhung the tich dung dich bang nhau (chn ST: hat chat tan phai cling kieu can trot). Vi du: Dung dich NaOH 2M, nghia 1a trong 1 lit dung dich nay có 2 mol hay 2 mol x 40 g/mol = 80 g NaOH. Dung dich chila phenobarbital 0,001M Ira NaC1 0,1M, nghia la trong 1 lit dung dich nhit the cal 0,001 mol x 232,32 g/mol = 0,2323 g phenobarbital (C12H72N2 03= 232,32) va 0,1 mol x 58,45 g/mol = 5,8450 g NaCl (M = 58,45). Trong 1 lit dung dich NaC1 1M có 1 mol x 58,45 g/mol = 58,45 g NaCl. Xem NaC1 dien ly hoan toan thanh cac ion, thi trong 1 lit dung dich nhu the cling có 1 mol ion Nat (23 g Nat) va 1 mol Cl-(35,45 g CU. Nguoc lai, dung dich Na2CO31M c6 trong 1 lit dung dich cua no 1 mol C032-(60 g CO3`-) va 2 mol Na+ (2 mol. x 23 g/mol = 46 g Nat), \Ted dieu kien gan dung rang trong dung dich, cif 1 phan tii natri carbonat thi dien ly ra 1 ion CO3`'-va 2 ion Nat. 73 - N6ng d6 &tong Wong (N): Vi du: H2SO40,5N la dung dich child 0,5 ducing hiving gam H2SO4trong 1 lit dung dich. Khal niem during Wong dm 1 chdt xudt phat tii dinh ludt &tong 1-acing dia Dalton,neu ra nam 1792 (xem chtiong 1). Goi &tong hfc.ing mot chdt la E. to có the neu cdc Ong thlic tinh E trong cdc phdn ixng trao d6i va oxy hod sau: Kheii hrong nguyen tir Enguycm Vi du: Eoxy Hod tri 16 8 2 Kh6i ltrong ion I Dien tich ion I Vi du: EA,,* E so4- 27 9 3 96 48 2 Eacitl Khoi lacing phan dr acid S6 ion fr dien ly tir mot phan tir acid Vi du: EFici 36,45 = 36,45 1 98 Ehase EH2S02 = 49 Kh6i lining phan tir base S6 ion OH-dien ly tir mot phan tir base Vi du: ENaOH 40 40 1 Kh6i luong phan tir mu6i IDien tich ion (throng hoac am)I x S6 ion (throng hoac am) 342 VI du: EA, ,(SO4)3 = 57 • 3x2 74 Khoi luting tidu phan (phan tir, nguyen tir, ion) EOx(Kh) S6 electron nhdn (hoac cho) cua mot tidu phan Bang oxy hod (hoac dang khir) day, Eox(Kh)la during Wong cua clang oxy hod hoac cua clang Vi du, tim during luring dm chat oxy hod va chat khil.trong phan 2KMnO4+ 10FeSO4 + 8H2SO4= 2MnSO4+ 5Fe2(SO4)3+ K2SO4+ 8H2 0 Can cit theo s6 electron ma met phan tii KMnO4nhan bang 5 va s6 electron ma mot phan tii FeSO4cho bang 1, ta xdc dinh dtfoc dating luting cUa chat oxy hod. la: EKNino4 158 = 31,6 5 va during Wong caa chat khit la: EFeSO4 151,8 = 151,8 1 Vi hod tri cUa nguyen to, s6 H+ hay OH-dien ly dm acid hay base, se; electron nhdn hodc cho cua chat oxy hod hoac chat khii c6 the thay doi tuST theo dieu kien cua phan ling, nen duong ltiong. cita met chat cling c6 nhting gia tri bi6n dei. Dicing Wong là met. dai luting khong c6 this nguyen. Trong hod hoc ngtioi ta thuong dung: + Diking tong gam ciia mot chat la kh6i Wong cilia chat do bi6u dien bang gam Ira c6 tri s6 bang &tong Wong cila no. + Mili &long luring gam, l(ST hieu mE, bang 1/1000 &tong Wong gam va lay don vi Main Wong la miligam. Vi du, c6 cdc cong dr& tinh sau: Khe luring chit (g/mol) Diking liking gam cilia chit (g/E) = SO during itking/mol Mili during luring gam cilia chit (mg/mE) = Kh6i luring chit (mg/mol) S6 during lu'cing/mol TraOng hop chat phan tan trong dung dich thi tit cac cong dr& tren c6 the suy ra: Du'dng luring gam cilia chit (g/E) = S6 gam chit/lit S6 clu'cing luring/lit 75 S6 miligam Mili &Ring lacing gam cila chat (mg/mE) = S6 mili during lacing/lit Vi du: Biet trong 1 lit huyet Wong cila mau ngi.thi có 100mg Ca'. Tinh: a. S6 mili &long Wong gam dm Ca' trong 1 lit buy& Wong? b. S6 miligam CaC1,.2H2 0 de pha 750m1 dung dich có n6ng do ion Ca' wong &wing trong huyet Wong? Gidi: a. E C a -` 40 2 = 20 g/E hoAc 20 mg/mE ta có: 100 mg/lit 20 mg/mE = S6 mili &rang lacing/1ft \Tay, s6 mili doing Wong cUa Ca"/lit (huyet Wong): 100 mg/lit 5 mE/lit (huyet ttiong) 20 mg/mE ECaCI,.211,0 147 b. ta co: 1 x 2 = 73,5 g/E hoac 73,5 mg/mE 73,5 mg/mE = S6 miligam chSt/lit 5 mE/lit Nen, s6 miligam chat (CaC12.2H20)/lit = 73,5 mg/mE x 5 mE/lit 367,5 mg/lit De pha 750m1 dung dich can: 750 ml 1000 ml N6ng d6 molan (m): x 367,5 mg = 275 mg CaC12.2H20 N6ng do molan khong bi bien doi theo nhiet d6, vi khac vdi th.4 tich, khol Fong dung moi khong phu thu6c vao nhiet d6. Vi du: Dung dich NaC1 0,173m trong dung moi nuoc, nghia la có 0,173 mol NaCl trong 1000 g mioc, do chinh la dung dich NaC1 1% theo kh6i luring. - N6ng d6 phan mol (X): Neu nAla s6 mol dung moi A va nnlà s6 mol chat tan B, thi ang d6 phan mol cua chat tan B la: 76 XB n B 11 A n B va ang d6 phan mol cita dung mai A la: XA nA nA+ n8 Hiking nhien: XA XB = 1 Vi du: Tinh ang d6 phan mol cua cac chat trong dung dich g6m 142 g isopropanol (C3H7OH) va 58,0 g nti6c. Gidi: 142 g C3H7OH S6 mol C,H7OH = — 2,36 mol C3H7OH 60,09 g C1H7OH/1 mol C3H7OH S6 mol nti6c = , 58,0 g H20 = 3,22 mol H2O 18,02 g H2 0/1mol H2 0 SOmol mol C3H7OH 2,36 mol x c,H7ou = Tong so mol dung dich = 2,36 mol + 3,22 mol = 0,423 SO mol H2O 3,22 mol X H20 = = = 0,577 T6ng so mol dung dich 2,36 mol + 3,22 mol XC,H2OH + X H20 = 0,423 + 0,577 = 1 1.3. Can bAng pha Qua trinh hinh thanh va nhang dac tinh ciia dung dich lien quan chat the den can bang va Nen d6i cac pha. Quy tac pha cim Gibbs cho bie't quy luat chinh xac va tang quat ve mat nhiet Ong he hoc d6i vdi tat ca cac he can bang. Cac khai niem va dinh nghia: + H" ddng the' là he ma cac phAn khac nhau cua no c6 ciing thanh phan, ding tinh chat hod hoc va nhiet Ong. + HO di the' la he ma a cac phan khac nhau cua no thi khac nhau ve thanh phan va cac tinh chat hoa hoc, nhiet dOng. + Pha la tap hop cac phan d6ng the trong he c6 thanh phan, tinh chat d6ng nhat va drfoc gioi han vdi cac phan d6ng the khac c4a he bai cac mat phan each ro ret. 77 S6 pha trong he duoc ki hieu bang chit c1). He chi c6 mot pha = 1) la he delng the. He chiia 2 pha trO > 1) la he di the. Vi du: Nttoc trong c6c la met he do'ng the, chi có met pha lOng = 1). Them cac cuc nuoc da vao c6c nuoc thi duoc he di the Om 2 pha = 2): pha long là nuoc va pha ran IA cac cuc nuoc da. Hoac d sit phan huY' calci carbonat c6 can bang: CaCO3(r) CaO (r) + CO2(k) ton tai 3 pha = 3) Om mot pha khi tao bOi CO,, met pha ran tao bai CaCO3va pha ran this hai tao bat CaO. • Cdu tic' la cac chat hod hoc cc-) mat trong he. O cac vi du tren thi he 2 pha (Ntteic H Ntteic da) chi có met cau tit la H2O; con d hg 3 pha (can bang phan huY calci carbonat) có 3 eau tit la CaCO3, CaO va CO2. + So-cdu d'Oc lap, duoc ki hieu bang chit C, la so-cat' tit tot thieu du de mo to thanh phan dia. he. N6i cach khac, do la s6 cau tit t6i thieu ma khi da bigt n6ng do cila chung la du de' xac dinh thanh phdn cua he. Ghia s6 Caul tit va s6 cau tit dOc lap (C) co mo'i quan he: C = S6 cau tit - S6 phtiong trinh lien he giiia cac cau tit (8-1) VI du, có can bang sau: PC15(k) PC13(k) + C12(k) thi C = 3 - 1 = 2 eau tit dOc lap, vi he g6m 3 cat' tii nhung c6 1 pinking trinh lien he Oita. chung. Sa di nhu vay vi chi can bigt n6ng do dia. 2 cau tit la c6 the suy ra n6ng d6 cua cau tit this 3 nho vao hang s6 can bang cila he. Theo do, thanh phan cua ca he •duoc xac dinh. TrUang hop giiia cac eau tit khong c6 pinking trinh lien he nao thi so-cau tit dOc.lap C = s6 cat' tit trong he. + Sdbiftc tu' do, Id hieu bang chit F, la s6 thong s6 Wang de cila he c6 the thay dOi tug Y ma khong lam thay de;i s6 pha va s6 cau tit cila cac pha do. Day chInh la s6 thong s6 doe lap cim he, chu y6u là nhigt de, ap suat va n6ng clO. — Quy tac pha: Quy tac pha do Gibbs thigt lap nam 1876 bang con dating nhiet deng. Do ld met dinh luat tang quat, chInh xac va don gian cho phep du doan sti thay d6i s6 pha trong he phu thuOc vac thay do"i dieu kien ben ngoai va vao s6 cat' tit dee lap. Bieu thiic cim quy tac pha &toe vigt: 78 F = C — + 2 (8-2) 6 day, F là s6bAc tit do (s6 th6ng s6 ct6c lAp cira he) C là s6 ciu tit d6c lAp 4:1) la. s6 pha va s6 2 là dai dien cho 2 thong s6 ben ngoal c6 the anh huang den he la ap suit va nhiet d6. VAy, doi vdi he can bang chi chiu anh hai ye'u to ben ngoai là hp suit va nhiet d6 thi s6 134 t4 do ciia he bang s6 ciu tit d6c lAp trif di s6 pha Ong voi. 2. Vi du: He mot cau tit là mi6c, s6 CAI tit d6c lap cling là 1 (C = 1), c6 cac truang hop sau: + N6u he chi c6 nti6c lOng ((l) = 1) thi: F = 1 - 1 + 2 = 2 He c6 2 bAc tti do, nghia là ta c6 the thay d6i tuS7 y nhiet do (trong khoang tit 0°C den 100°C) va bat ki ap suit nap ma van khong lAm thay d6i s6 pha va ciu tit dia he. D6 IA he nhi bi6n. + N6u he can bang là I\TV6c 'Ong Hoi nude = 2) thi: F = 1 — 2 + 2 = 1 He co 1 bAc tit do, nghia là khi thay d6i nhiet do thi ap suit hdi dm he thay d6i mot each don tri: ap suit hdi nti6c bac) hoA can bang vdi nti6c lOng là hoan toan xac dinh 6 tai moi nhiet d6. Noi each khac, tai moi nhiet d'6 xac dinh chi c6 mot gia tri cua ap suit hdi bao hoa cira nti6c. D6 là he nhit bi6n. + Neu he can bang co 3 pha(CD= 3) Hai ntrac Nireic Nuot da thi: F = 1- 3+ 2 = 0 He khong c6 bAc tit do nAo ca, nghia 1a nhiet do va ap suit cira he ham toan xac dinh (6 T = 273,16°K va ap suit hdi nude P = 0,006 atm). Ngithi ta khong th6 duy tri can bang nay ne'u thay d6i du chi mot thong s6 nhiet do hoac ap suit hdi. Goi day là he bit bi6n. Ke't qua van dung quy tic pha cho nude tren day cling ap dung dtioc cho tit ca cac he mot ciu tit (he mot chit nguyen chit) - xem tom tat a bang 8.4 va diloc the hien tren sd do pha cua phdn ti6p theo. 79