Thiết Kế Bài Giảng Hóa Học 12 Nâng Cao Tập 2

"Thiết Kế Bài Giảng Hóa Học 12 Nâng Cao Tập 2 🔙 Quay lại trang tải sách pdf ebook Thiết Kế Bài Giảng Hóa Học 12 Nâng Cao Tập 2 Ebooks Nhóm Zalo CAO CU GlAc (Chu bien) NHA XUAT BAN HA NOI TS. CAO CUGIA C (Chu bign) - ThS. HO THANH THUY THIET KE BAI GIANG NflNQCflO-TilPHfll NHA XUAT BAN HA NOI ChiroTig 5 DAI CirONG VE KIM LOAI Bai 19. KIM LOAI VA HQP KIM A. MUC TIEU BAI HOC 1. Kiln thiPc HS biit: • Vi tri cua kim loai trong bang tuan hoan. • Cau tao ciia nguyen ttr Icim loai. • Kliai niem, tinh chat va ung dung cua hop kim. HS hiiu: • Nhirng tinh chat vat li va tinh chat hoa hpc cua kim loai, hop kim. • Nguyen nhan gay ra tinh chSt vat li chung, tinh khu cua kim loai. 2. KT nang • Ren luyen kT nang: Tu vi tri cua kim loai suy ra cau tao va tinh chSt. • • D§n ra dugc nhiing phan ijng hoa hoc va thi nghiem hoa hoc chung minh cho nhirng tinh chat cua kim loai. • Ren luyen kT nang giai bai tap ve kim loai. 3. Tinh cam, thai do Biet dugc nhiing tinh chat quy gia cua kim loai lam cho HS co y thuc bao ve va su dung tiet kiem kim loai. B. CHUAN B! CUA GV VA HS • GV: - Bang tuan hoan cac nguyen to hoa hgc. - Chuan bi mgt so thi nghiem minh hoa cho tinh khir ciia kim loai. - Dung cu: Ong nghiem ca nho, ong nho gigt, den c6n,... - Hoa chat: + Cac kim loai: Al, Cu. Fe (dinh sit sach). + Cac dung djch: axit H2SO4 loang, H2SO4 dac, HNO3, CUSO4 • HS: Xem truac noi dung bai hgc. C. TI^N TRiNH DAY - HOC Hogt dpng ciia GV Hogt dpng cda HS A - KIM LOAI Hogt dpng 1 I. VI TRI CUA KIM LOAI TRONG BANG TUA N HOAN GV chieu bang tuan hoan len man hinh (hoac treo baag tuan hoan co to mau cac nguyen to len bang) cho HS quan sat. GV huong dan HS tim ra vi tri ciia kim loai trong bang: - Kim loai la cac nguyen to co to mau vang a trong bang tuan hoan. - Phi kim la cac nguyen to co to mau tim a trong bang tuan hoan. Yeu cau HS xac dinh vi tri cua kim loai. GV bo sung: Ngoai each xac dinh a tren thi kim loai nam a: - Khoi nguyen to s (trir H, He) - Mgt so a khoi nguyen to p - Toan bg khoi nguyen to d, f GV yeu cau HS nit ra ket luan ve vi tri ciia kim loai. HS: Quan sat, thao luan cho ket qua: Vi tri kim loai gom: - Nhom IA dgn VIA (Nhom IA trir H nhom IIIA tru B) va mgt phan nhom IVA,VA, VIA. - Nhom IB dSn VIIIB. - Hai ho Lantan va Actini. HS thao luan cho ket qua: - Kim loai chiem da so vi tri trong bang tuan hoan. - Kim loai nam a phia duai ben trai ciia bang tuan hoan. Hogt dpng cua GV Hogt dpng cua HS Hogt dpng 2 II. TINH CHA T VAT LI 1. Tinh chat vat li chung GV giai thieu: 0 dieu kien thuang. cac kim loai deu a trang thai ran (trir Hg), CO tinh deo, dan dien, dan nhiet va co anh kim. Vay the nao la tinh deo, tinh dan dien, tinh dan nhiet, anh kim va tai sao kim loai CO cac tinh chat tren chung ta se nghien cuu timg tinh chat cu the. a) Tinh deo GV yeu cau HS nghien cim SGK va cho biet: - The nao la tinh deo? - Giai thich. HS lang nghe HS thao luan nhan xet va cho ket qua: - Tinh deo ciia vdt lieu la tinh bi bien dang khi chiu ap luc ben ngoai hoac nhiet tac dung va van giu dugc trang thai bien dang do khi thoi tac dung. - Gidi thich: Kim loai co tinh deo la vi cac ion duang trong mang tinh the kim loai CO the trugt len nhau de dang ma khong tach ra khoi nhau nha nhiing electron tu do chuyen dgng dinh ket chiing vai nhau. e.e;© ©•©•©. e:©'© ©:©.© •: Electron tir do ® : Ion duang kim loai ©:©©! i » j . • • r r^.©.# Hogt dpng cua GV GV bo sung: Kim loai c6 tinh deo Ion nhat la Ag sau do la Al, Cu.... b) Tinh ddn diin GV yeu cau HS nghien cim SGK va cho biet: - The nao la tinh dan dien? - Giai thich. GV bo sung: Kirn loai dan dien tot nhat la Ag, sau do den Cu, Au, Al, Fe.... c) Tinh ddn nhiet GV yeu cau HS nghien cuu SGK va cho biet: - Th6 nao la tinh din nhiet? Giai thich. GV b6 sung: Thuang caic kim loai dan dien tot cung dan nhiet tot. Hogt dpng cua HS Tinh ddn diin la tinh chit cua vat lieu khi gin vao 2 diu vat lieu mgt hieu dien thg thi tao thanh dong chuyen dai co huang cua electron tir cue am sang cue duang. Gidi thich: Do trong kim loai co cac electron tir do, chuyen dgng tir do trong mang tinh the, khi co hieu dien the lap tiic cac electron tu do chuyen dgng thanh dong co huong tao ra dong dien. - Tinh ddn nhiet la tinh chat cua vat lieu CO th6 truy6n nang lugng (nhiet) tir vi tri nay den vi tri khac. - Gidi thich: Do kim loai co mat cac electron tu do trong mang tinh the. Cac electron trong viing nhiet do cao co dgng nang lan, chuyen dgng hon loan va nhanh chong sang viing co nhiet do thap han, truyen nang lugng cho cac ion duang a viing nay nen nhiet lan truyen dugc tir viing nay den viing khac trong khdi kim loai. Hogt dpng cua GV Hogt dpng cua HS d) Anh kim GV yeu ciu HS nghien cuu SGK va cho bi^t: - The nao la anh kim? - Giai thich. GV huang dan HS ket luan vin de: Nguyen nhan gay ra tinh chat vat li chung ciia kim loai? 2. Tinh GV giai thieu: Ngoai cac tinh chat tren kim loai con co mgt so tinh chat vat U khac nhu: Tinh cung, khoi lugng rieng, nhiet do nong chay, nhiet do soi. a) Khdi luang riing GV cho HS nghien cim SGK va yeu ciu HS cho biet sir bien doi cac tinh chit: Tinh cimg, kh6i lugng rieng, nhiet do nong chay, nhiet do soi. HS thao luan cho ket qua: Anh kim la anh sang thu dugc khi kim loai hap thu anh sang trang va phan xa ra anh sang co buac song dac trung cho timg kim loai Gidi thich: Do cac dam may electron tu do trong tinh the kim loai hap thu phan xa hau het nhirng tia sang nhin thay dugc, do do kim loai co ve sang lap lanh ggi la anh kim. HS nhan xet: Tinh chdt vdt li chung ciia kim logi gdy nen boi su cd mat ciia cdc electron tu do cd mat trong tinh thi kim logi. chat rieng HS nghe giang. HS nghien cuu SGK va nhan xet Khoi lugng rieng ciia cac kim loai khac nhau ro ret nhu: - Ll (D = 0,5 gam/cm ) la kim loat nhe nhat. - Os (D = 22,6 gam/cm ) la kim loai nang nhat. Hogt dpng cua GV b) Nhiet dp ndng chay c) Tinh cirng Hogt Hogt dpng cda HS Nhiet do nong chay cua kim loai dao dgng trong mgt khoang rgng nhu: Kim loai co t°,thip nhit la Hg(-39"C) Kim loai co t°,cao nhit la W(3410°C) Tinh cicng ciia kim loai ciing rat khac nhau nhu: Cr la kim loai cirng nhat, kim loai ki6m thi rat mem co the dung dao de cat. dpng 3 II. TINH CHA T HO A HO C CHUNG CUA KIM LOAI GV huong dan HS rut ra tinh chat hoa hgc ca ban ciia kim loai: - Dac diem cau tao cua nguyen tir kim loai (so electron hoa tri). - Du doan xu huang ciia kim loai de CO dugc cau hinh ben cua khi hiem. - Suy ra tinh chat chung cua kim loai. Hogt \. Tac dun HS thao luan nhan xet cho ket qua sau: - Kim loai thuang co it electron (l-3e) a lop ngoai ciing. - Xu huang cho electron de dat dugc cau hinh ben. - Tinh chat chung cua kim loai la tinh khir. M ^M""+ne dpng 4 GV giai thieu: Kim loai co the tac dung vai nhieu phi kim a nhiet do cao. Yeu cau HS cho biet san pham, lay vi du minh hoa. 5 vol phi kim HS thao luan cho ket qua: Kim loai tac dung vai phi kim tao thanh muoi (trir oxi) F/t/w.-2Fe +3C12 ^—> 2FeCl3 2A1 + 302 -^-^ 2AI2O3 Fe + S -^ ^ FeS Hogt dpng cda GV Hogt dpng cua HS Hogt dpng 5 2. Tac dung voi dung dich axit a) Ddi v&i dung djch HCl, H2SO4 hang GV neu vin At. Cac dung dich axit HCl, H2SO4 loang co tinh oxi hoa. Nhung tai sao chi tac dung dugc vai cac kim loai dimg truac H trong day hoat dgng? San pham phan ung thu dugc la gi? GV huang dan HS Giai quyet vin dh, Viet cac phuang trinh hoa hgc minh hoa GV bo sung: Cac kim loai da hoa tri thuang bi oxi hoa len so oxi hoa trung +2 binh nhu: Fe, Cr... Fe —> Fe b) Ddi v&i, H2SO4 (dgc,ndng), HNO3 GV dat vin dk: Tai sao HNO3, H2SO4 dac lai tac diing dugc vai hau het cac kim loai (trir Au, Pt) Trong khi axit HCl, H2SO4 loang khong co dugc tinh chat nhu vay? GV huang dan HS giai quyet van de. - S6 oxi hoa cua cac nguyen to trong phan til- axit ITNO3, H2SO4. HS thao luan de giai quyet van de: Cac phan tir axit HCl, H2SO4 loang co tinh oxi hoa do ion H trong phan tir axit the hien nen chi tac dung vai cac kim loai CO tinh khir manh han hidro. San pham phan img la muoi va H2. Phuang trinh hoa hgc phan ung: Zn +HC1 -> ZnCb +H2 t Zn + H2S04 ^ ^ ZnS04+ H2T HS thao luan de giai quyet vin de duai su huong dan ciia GV: + 1 +6-2 +1 +5 -2 - So oxi hoa: H2 SO4, H N O3 Hogt dpng cua GV - Kha nang oxi hoa cua cac nguyen t6. - San pham ciia phan img. - Viet cac phucmg trinh phan img minh hoa. GV nhan xet va bo sung: - Tuy vao dieu kien phan ung ma cho ra cac san pham khir khac nhau. - Thuang cac kim loai bi oxi hoa len so oxi hoa cao. - Axit FtN03 va H2SO4 dac, ngugi lam thu dgng hoa Al, Fe, Cr... Hogt dpng ciia HS + 1 +5 +6 - Kha nang oxi hoa chi co H,N, S nhung dg oxi hoa dugc cac kim loai yeu +5 +« nhu: Cu, Ag... thi chi co thd la N, S . - San pham ciia su oxi hoa. S la: SO2, S, H2S N la: NO2, NO, N2O, N2, NH4NO3. - Phuong trinh hoa hgc: 3Cu + 8HNO3 -> 3Cu(N03)2 + 2N0 1 + 4H2O 2Ag + 2H2SO4 '° > Ag2S04 + SO21 + 2H2O Fe+6HN03dac '° > Fe(N03)3+ 3NO21 + 3H2O Hogt dpng 6 3. Tac dung voi dung djch muoi GV lam thi nghiem: Ngam 1 thanh sat da (cao sach gi) vao dung dich CUSO4 loang sau 1 thai gian, cho HS quan sat va yeu cau. 10 HS quan sat va nhan xet Hogt dpng cda GV - Quan sat hien tugng. - Giai thich. - Viet phuang trinh hoa hgc minh hoa. Hogt dpng cua HS - Hien tugng: dung dich CUSO4 nhat mau dong thai tren thanh sat co Cu kim loai mau do bam vao thanh sat. - Gidi thich: Fe co tinh khir manh hon Cu. Khir Cu^^ thanh Cu. Nong do CUSO4 giam lam mau xanh nhat dan, dong thai Cu kim loai mau do tao ra bam len thanh sat. - Phuang trinh hoa hgc Fe + CUSO4 -> FeS04 + Cu GV lam tiep thi nghiem: Cho 1 Na vao dung dich CUSO4 loang HS quan sat va yeu cau: - Quan sat hien tugng. mau Cho HS quan sat va nhan xet - Hiin tugng: Thay mau Na tan dan dong thai c6 khi bay ra va dung dich nhat mau, co ket tua mau xanh nhat xuat hien. - Giai thich bang phuong trinh hoa hoc. hiem GV yeu ciu HS so sanh 2 thi ng dh rut ra ket luan. GV khic sau kien thuc: - Gidi thich: Ban dau mau Na tac dung vai nuac lam mau Na tan va co khi 2Na + 2H2O -> 2NaOH + H21 Sau do NaOH trao doi vai CUSO4 tao thanh ket tua Cu(0H)2 CuS04+2NaOH->Cu(OH)2 + Na2S04 Kit ludn: Tuy vao ban chat kim loai ma san pham tao ra la khac nhau. HS ghi bai. Dieu kien kim loai tac dung vai dich mu6i tao ra kim loai mai. dung 11 Hogt dpng cua GV - Kim loai co tinh khir manh han kim loai trong muoi. - Kim loai khong tac dung vai nuac a nhiet do thuong. - Muoi cua kim loai tao ra phai tan. GV bo sung ngoai cac tinh chit tren thi kim loai con co cac phan img khac: - Tdc dung vai oxit kim logi: Vi du Al tac dung dugc vai Fe203, Fe304, CuO. - Tdc dung vdi oxit phi kim Vi du: Mg CO the khu dugc CO2, SO2... - Kim logi Al, Zn, Be... tdc dung vai dung dich baza. Yeu cau HS viet phuong trinh hoa hgc minh hoa. Hogt dpng cda HS Phuang trinh hoa hgc 2A1 + Fe203 — ^ AI2O3 + 2Fe Mg + CO2 -^ ^ MgO + CO 2Al+2NaOH+2H20-»2NaA102 + 3H2 Hogt dpng 7 4. Tac dung v6"i nu-dc GV yeu cau HS viet cac kieu phan img ciia kim loai ma HS da timg biSt? GV thong bao: Vay nhirng kim loai nao thi co phan ung theo kilu ciia Na, theo kieu ciia Fe. Co the xet nhu sau: - Cac kim loai nhom IA, IIA (trir Be, Mg) CO tinh khir manh tac dung vai nuac a nhiet do thuong tao ra bazo tan va hidro. - Cac kim loai co tinh khir yeu han tac dung vai nuac o nhiet do cao tao ra oxit kim loai va hidro. 12 HS viet phuang trinh hoa hgc 2Na + 2H2O -> 2NaOH + H21 Fe + H2O —i ^ FeO + H21 HS ghi bai. J Hogt dpng cda GV - Cac kim loai co tinh khir rat yeu nhu Ag, Au, Pt... thi khong cac dung dugc vai nuac. B - HOP KIM Hogt dpng 8 I. DINH NGHIA Hogt dpng cda HS GV chieu len man hinh tranh anh hoac cac mau vat sau va giai thieu: - Manh duyra la hgp kim cua Al, Cu, Mn, Mg. - Thanh thep (1 mieng gang) la hgp kim ciia Fe, C. - Day chuyen, nhan, bong tai lam bing vang tay la hgp kim ciia Au, Cu, Ag. Yeu ciu HS cho biit: Thanh phan ciia cac hgp kim tren c6 gi giong va khac nhau. / Tir do neu khai niem hgp kim. GV bo sung: - Hgp kim khong phai la hon hgp thong thuang thu dugc khi trgn 2 chit vol nhau. Ma la san phim thu dugc khi nung chay hon hgp kim loai vai kim .loai hay kim loai vai phi kim. - Hap kim c6 ciu tao tinh the va dugc chia lam cac loai: HS quan sat thao luan va nhan xet: Gidng nhau: Deu co thanh phan la kim loai. Khdc nhau: Ngoai kim loai do con c6 kim loai khac hay phi kim trong hgp kim. Dinh nghia: Hgp kim la vat lieu kim loai c6 chira mgt kim loai ca ban va mgt so kim loai va phi kim khac. 13 Hogt dpng cda GV + Tinh the hon hgp. + Tinh the dung dich ran. + Tinh the hgp chat hoa hgc. Hogt dpng 9 Hogt dpng cda HS GV giai thieu: II. TINH CHA T CU A HO P KIM HS nghe giang va ghi bai. - Tinh chdt hod hoc cua hgp kim thi thuang CO tinh chat ciia cac don chat cau tao nen hgp kim. Vi du: Hgp kim Cu-Zn thi co tinh chat cua Cu va tinh chat cua Zn. - Tinh chdt vdt li: Co nhiSu thay doi so vai tinh chat cua cac dan chat. GV neu cac vi du sau ve don chat va hgp chat - Vang 99,99% dep nhung mem, nhirng d6 diing bing vang 99,99% de meo va mon. De khac phuc nhung nhugc di§m do nguai ta diing hgp kim ciia vang vai Ag, Cu de lam do trang sire va due tien. - Do dan dien cua Cu rit tot (dung thu 2, sau Ag). Do dan dien ciia dong giam nhanh n8u co lan tap chat. Do vay, day dien la d6ng c6 do tinh khiet den 99,99%. - Nhiet do nong chay ciia Sn (232 C) Nhiet do nong chay ciia Pb (327,4 C) -> Nhiet do nong chay cua hgp kim Sn-Pb (thiec han) la 2 lo V 14 HS thao luan va nhan xet. - Tinh cimg: Hgp kim thuang cung han cac kim loai thanh phan. - Do ddn dien ciia hgp kim giam nhieu so vai kim loai don chat. - Nhiet dp ndng chay cua hgp kim giam so vai kim loai dan chat. Hogt dpng cua GV Yeu cau HS nhan xet sir biln d6i tinh chat vat li ciia hgp kim. Hogt dpng 10 Hogt dpng cda HS III. inVG DUNG CUA HOP KIM GV Chieu len man hinh tranh, hinh anh bang powerpoint giai thieu ve nhung ling dung cua hgp kim. HS ghi bai - Thep khong gi (thep inox): Fe(74%)-Ni(8%)-Cr(18%): Chd tao dung cu y te, nha bep. - Thep Mn rat ben, chiu dugc va dap manh, dung de che tao duong ray xe lira, may nghien da. - Thep W-Mo-Cr rit cung dii a nhiet do cao, diing ch8 tao luai dao cat ggt kim loai cho may tien, may phay. - Duyra hgp kim Al(95%), Cu(4%), Mn-Mg-Si(l%). Duyra nhe gin nhu nhom nhung lai rit cung, cimg gap 4 lan nhom tuc gin bing thep ma lai nhe bang 1/3 thep. Duyra b6n. Diing lam vat lieu ch6 tao may bay, 6 to. Hogt dpng 11 CUNG CO BAI VA BAI TAP VE NHA GV chidu cac bai tap sau len man hinh cho HS thao luan cung c6 ngi dung bai hgc: Cau 1. Kim loai nao trong cac kim loai sau tac dung dugc vai ca 4 dung dich muoi: Zn(N03)2, AgN03, CuCb, AICI3? HS quan sat theo luan cho ket qua Cau 1. Chgn dap an D 15 Hogt dpng cda GV A. Fe B. Al C. Cu D. Mg Cau 2. Dot chay hoan toan 4,04 gam hon hgp bot ba kim loai Cu, Al, Fe thu dugc 5,96 gam hon hgp 3 oxit. DS hoa tan het hon hgp ba oxit nay can V lit dung dich HCl IM. Gia tri ciia V la iCho 0=16. Al=27, Fe=56, Cu=64) A. 0,12 lit. B. 0,14 lit. C O, Hit. D.O, 24 lit Cau 3. Nhom chat nao sau day deu tac dung dugc vai dung dich NaOH? A. Al, Al203,NH4Cl, Si B. Si. CI2, FeCh. N2 C. Si, CI2, S,N2 D. Al, Fe, Cu(N03)2, KHSO4 Hogt dpng cua HS Cau 2. Chgn dap an D Cau 3. Chgn dap an A Bai tap ve nha: 1,2,3,4,5,6,7,8,9, 10, 11, 12 (SGK). D. HU'ONG DAN GIAI BAI TAP TRONG SGK 1. Chgn dap an B 2. Chgn dap an C 3. Chgn dap an C 4. Dung. 5. Vi tri ciia kim loai trong bang tuan hoan: - Cac nguyen to s (nhom IA, IIA). - Cac nguyen t6 d (nhom IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, IIB). - Cac nguyen to f (hg lantan va hg actini). - Mot phin cac nguyen to p. 16 Vl tri kim loai co tinh khir manh nhat: Goc trai phia duoi bang, do la nguyen t6 Cs. Vi tri phi kim co tinh oxi hoa manh nhit: Goc phai phia tren bang, do la nguyen td F. Cau hinh electron nguyen tir: Cs: [Xe]6s' F: 1 s^2s"2p' 6. Cau hinh electron nguyen tir va ion: Thidu: Na:lsV2p'3s' Na": ls-2s V Fe: [Ar] 3d'4s- Fe"": [Ar] 3d' Fe'": [Ar] 3d' 7. a) Truang hgp xay ra phan img Fe + CUSO4 -^ Fe + Pb(N03)2 ^ Vai tro cac chat tham gia phan img - Chat khir: Fe - Chit oxi hoa: Cu^", Pb"" b) Phudng trinh hoa hgc dang ion thu ggn: Fe + Cu^" -> Fe'" + Cu Fe + Pb^" -^ Fe^" + Pb 8. a) Cu + Fe2(S04)3 ^ CUSO4 + 2FeS04 Cu + 2Fe'" -> Cu"" + 2Fe^" Fe + CUSO4 -^ Cu + FeS04 Fe + Cu"" -^ Fe-" + Cu b) So sanh: Fe co tinh khir manh han Cu; Fe co tinh oxi hoa manh han Cu" ; Cu c6 tinh oxi hoa manh han Fe" . 9. a) Cho dung dich 2 muoi tac diing vai bgt Fe du. Phan img xong, Igc bo bgt Fe du, nuoc lgc la dung djch FeS04. HS viet phuang trinh hoa hgc b) Ngam hon hgp bgt Cu, Zn, Pb trong dung dich Cu(N03)2 du. Sau phan irng, lgc dugc chat ran la Cu. HS viet phuang trinh hoa hgc. 2-TKBGHOAH M^" + Cu (2) Dat X (g) la kh6i lugng mol ciia kim loai M. n la s6 mol kim loai M tham gia phan ung. a la khdi lugng la kim loai M ban diu. Theo (1) khi co nx (g) kim loai M tham gia phan irng, sinh ra 207n gam Pb. Ta c6 phuang trinh dai so: 207-nx 100% = 19% a n(207-x) /o^. Rutra: a = -^-- - .100 (3) Theo (2) khi c6 nx (g) kim loai M tham gia phan img, sinh ra 64n gam Cu. Ta CO phuong trinh dai so: nx-6 4 -.100% = 9,6% a Rutra: a = ^^^.10 0 (4) 9,6 Tir (3) va (4), ta co: il(207^100=i^^^^^.l0 0 ^x=112(g) . 19 9,6 Kim loai M co khdi lugng mol 112 la cadimi (Cd). 12. Giai tuong tu bai tap 8. Kim loai M co khdi lugng mol 65 g/mol la Zn. 18 E. TU- LIEU THAM KHAO De giai thich cac li tinh ca ban cua kim loai c6 the dua vao thuylt "khi electron" va thuylt vimg ndng lugng. 1. Thuyet "khi electron" Thuyet "khi electron" cho ring mang tinh the kim loai d thd rin va long bao gom dong thdi cac nguyen tir da bi ion hoa, tire la cac nguyen tir da bi tach mgt phan cac electron hoa tri cua minh. Cac electron hoa tri lien kit ylu vdi cac hat nhan nguyen tir, trong do cd mgt s6 chuyin dgng tu do de dang trong toan khdi kim loai, chuyen ddng hdn loan nhu cac phan tir khi. Vi thi c6 thi coi nhu cd khi electron chuyin ddng trong mang tinh thi kim loai. Kilu lien kit giira "khi electron" vdi cac nguyen tir va ion kim loai ggi la lien kit kim logi. Gidi thich: Bang thuyet "khi electron" cd thi giai thich dinh tinh cac tinh chit li hgc dac trung cua kim loai: • Kim loai cd anh kim vi "khi electron" trong ciu triic tinh thi kim loai tao ra cho kim loai kha nang phan chieu manh cac biic xa nhin thiy. Mgt sd kim loai cd mau vi chi hap thu mdt sd birc xa va phan chilu mdt sd biic xa nhin thay khac. Ddng cd mau do vi nd da hap thu cac biic xa ciing mau xanh. • Kim loai dan dien tdt vi "khi electron"chuyln ddng tir hon loan sang cd hudng khi lap mdt hieu dien thi d hai diu day din. Dun ndng, do dan dien giam vi tang su chuyen dgng hdn loan ciia "khi electron" va tang sir dao ddng cua nguyen tir hay ion kim loai lam can sir chuyin ddng cd hudng cua electron. • Kim loai dan nhiet tdt vi khi tang nhiet do d mdt cho thi d dd nguyen tir va ion kim loai dao ddng manh, truyen sang cac electron tu do, rdi tir cac electron tu do truyen sang cac nguyen tir va cac ion kim loai lan can... Cir the dao ddng ciia cac nguyen tir va cac ion trong toan khdi kim loai dugc tang cudng va trang thai nhiet cua khdi kim loai dugc thang bing nhanh chdng. • Kim loai cd tinh deo la nhd "khi electron" lien kit cac tieu phan (nguyen tir va ion kim loai) trong tinh the va chiing cd thi bi xe dich do chiu tac dung cua mdt lire ca hgc. Han che cua thuyet "khi electron" la khdng thi giai thich dugc mdt each triet de mire do khac nhau ve 4 tinh chat li hgc dac trung cua kim loai va khdng thi giai thich dugc cac tinh chat li hgc rieng cua mdi kim loai. 19 2. Thuyet vung nang luotig Thuyet viing nang lugng dua tren co sd phuong phap obitan phan tir (MO), la thuylt hien dai cd thi khic phuc nhirng thilu sdt cua thuyet "khi electron" ve cau true kim loai. Theo thuylt nay, kim loai rin hay ldng cd -cau true tinh the, nut mang la ion duang. Cac obitan nguyen tir (AO) hoa tri ciia cac kim loai dugc td hgp thanh cac MO chung cho toan bg tinh thi. Trong sir hinh thanh phan tir hai nguyen tu. sir xen phii giira 2 AO lien kit lam xuit hien 2 MO. Khi mdt nguyen tir thu ba dugc kit hgp vao phan tir nay thi cd sir hinh thanh 3 MO. Nhu vay neu tinh thi kim loai gdm N nguyen tir (N = 6.023.10^'^) thi sir xen phu ciia N AO se cho ta N (MO). Moi MO img vdi mdt trang thm nang lugng xac dinh. Vi so N rit ldn. nen N trang thai xich lai gin nhau tao nen viing nang lugng. Su khac nhau vl nang lugng ciia cac trang thai trong gidi han mdt vimg la vd ciing nhd be. chi bing khoang 10"^^ eV, nen cd thi coi viing nang lugng nhu mdt vach nang lugng lien tuc. Cac MO ciia vimg nang lugng tuong tu nhu cac MO bat dinh xir khap tinh the kim loai. Hinh 5.1 cho thiy sa dd hinh thanh cac mire nang lugng (tao ra viing nang lugng khi tang sd nguyen tir tuang tac). E 1 2 4 8 IG N Hinh 5.1. Sa 66 hinh thanh cac viing nang lugng khi tang lien tuc so nguyen tu trong tinh the kinn loai Su diln cac electron vao cac MO trong viing nang lugng xay ra theo thii tu nang lugng tang din va theo nguyen li Pauli (mdi MO tdi da 2e cd spin ddi song). Vay nlu tinh thi gom N nguyen tir, cac vimg nang lugng hinh thanh do sir xen phii cac AO s, p, d, f se chiia toi da 2N (viing s), 6N (viing p), 1 ON (vimg d) va 14N (vimg f) electron. Tuy thudc vao ciu hinh electron cua nguyen tir va tinh ddi ximg ciia mang tinh thi, viing chiia electron dam bao cho sir lien kit goi la viing hod tri (vimg chiia electron hoa tri) va viing trdng tren viing hoa 20 tri ggi la viing ddn. Neu viing hoa tri va viing dan khdng xen phu nhau thi cd mdt khoang gian doan ve nang lugng ggi la vimg cdm. 0 cac tinh the kim loai thudng xay ra sir xen phu nhau ciia viing hoa tri va viing dan. Trong chit ban dan viing cam cd chilu rgng AE = 0,1 - 3,0 eV va trong chit dien mdi (each dien) cd A E > 3,0 eV (xem hinh 5.2). v'ung dan Hoac Vung dan Vung hoa tri Vung dan Cac vung pliu len nhau Vung cam re Vung hoa tri ng Vung dan Viing cam hep Vung hoa tri Kim loai Vat each dien Vat ban dan Hinh 5.2 Cac electron hoa tri chuyen ddng tren cac MO chung cho toan bd tinh thi nen cd tac dung rang budc cac ion duong kim loai thanh mdt khdi. Gidi thich tinh chdt vdi li cua kim logi: • Theo thuyet viing nang lugng, vi cac electron hoa tri chuyen ddng tren eac MO ciia viing hoa tri tao ra nhirng dam may electron da lam tang kha nang phan chieu va giam kha nang hap thu cac buc xa nhin thay ma kim loai cd anh kim. Cung vi cd cac electron hoa tri chuyen ddng tren cac MO chung ma lam cho toan bd tinh the ludn ludn lien ket vdi ion duong thanh mdt khdi ddu chiu dugc tac dung ciia luc ca hgc ma kim loai cd tinh deo. • Tinh dan dien va dan nhiet tdt ciia kim loai dugc giai thich nhu sau: cac kim loai dan dien tdt nhat thudc nhdm IA va IB. Nguyen tir cua cac kim loai nay chi cd 1 electron hoa tri s nen vimg nang lugng cua tinh the kim loai mdi chira 1/2 sd electron tdi da. Trong tinh the chira N nguyen tii' thi cd N (AOs) ciia Idp ngoai cimg xen phii tao ra N (MO), lap thanh viing nang lugng gdm N mire. Vi cd N electron hoa trj nen so electron chi chiem N/2 mire (moi mire 2 electron). N/2 mire bi electron chiem tao thanh viing hoa tri. N/2 miic 21 con lai dang trdng tao thanh vimg dan. Cac miic bi chiem nam gan true tiep vdi cac mire trdng tao co hdi cho cac electron cd the chuyen dich dugc duai tac dung ciia dien trudng. Do dd kim loai nhdm IA va IB dan dien tot. Trong tinh the kim loai nhdm IIA va IIB sir xen phu ciia cac AOs ciia N nguyen tir ciing tao ra vimg N mire. Do mdi nguyen tir cd 2 electron s nen \ung nay phai dugc xep 2N electron, nghia la viing hoa tri da dugc dien dii. Tuy nhien, cac AOp ben ngoai ciing xen phu nhau thanh cac MO tao ra vimg nang lugng trdng p vdi 3N mire (vimg dan). Hai viing hoa tri s va vimg dan p xen phii nhau tao thanh viing lai hoa sp. Cac electron eiing chuyen dich true tiep theo cac mire cua vimg lai hoa sp khi cd tac dung cua dien trudng. Tuang tu vdi cac nguyen td chuyen tiep d (chang ban Cr 3d 4s ). Neu tinh thi gom N nguyen tir thi kit qua cua su xen phii ciia cac AOs ldp ngoai cimg tao ra vimg s gdm N miic va cua AOd ldp sat ngoai ciing tao ra vimg d gdm 5N mire. Su xen phii cua 2 viing s va d tao ra vimg lai hoa ds gdm 6N mire. Nguyen tir ciia nguyen td chuyen tiep nhu Cr chi cd 6 electron hoa tri nen tinh thi N nguyen tir chi cd 6N electron hoa tri va chi dien vao 6N/2 = 3N mire. Viing lai hoa ds cdn 3N miic trdng nen kim loai chuyen tiep dan dien tdt. Cac kim loai dan nhiet tdt nhd kha nang di chuyen tu do ciia cac electron hoa tri trong tinh the va truyen nang lugng tir phan ndng hon sang phan lanh hon. Khi dun ndng, dao ddng cua cac nguyen tir tai chd bi dun ndng trd nen manh hon, gay khd khan cho su chuyen ddng cd hudng ciia electron hoa tri tu do theo chieu ciia dien trudng hay tir phan ndng den phan lanh. Do do tinh dan dien va dan nhiet ciia kim loai giam khi nhiet do tang. Thuc nghiem cho thay khoang 1 electron trong sd cac electron hoa tri ciia nguyen tir kim loai gay ra tinh dan dien va dan nhiet, sd electron hoa tri con lai tham gia tao lien ket cdng hoa tri ben giira cac nguyen tir kim loai. Do do phan ldn cac kim loai chuyen tiep cd khdi lugng rieng, nhiet do ndng chay, nhiet do sdi va do cimg ldn hon nhieu so vdi cac kim loai khdng chuyen tiep. 22 Bai 20. DAY DIEN HOA CUA KIM LOAI A. MUC TIEU BAI HOC 1. Ki§n thii'c HS biit: • Cac khai niem: Cap oxi hoa - khir ciia kim loai, pin dien hoa, suit dien ddng va the dien cue. • Cau tao cua pin dien hoa, su chuyin dgng cua cac phin tir mang dien khi pin dien hoa hoat ddng. • Cac phan ung hoa hgc xay ra d catot (cue +) va anot (cue -) ciia pin dien hoa. • The dien cue chuan ciia kim loai. • Day the dien cue chuan cua kim loai va y nghTa cua nd. HS hiiu: • Cach sir dung day dien hoa de du doan chieu cua phan iing oxi hoa khir. • Cach xac dinh suat dien ddng chuan ciia cap pin dien hoa. 2. KT nang • So sanh tinh oxi hoa ciia cac ion kim loai, tinh khir ciia cac kim loai giira cac cap oxi hoa - khir. • Xac dinh ten va dau ciia cac dien cue trong pin dien hoa, tinh dugc suat dien ddng cua pin dien hoa. • Tinh dugc the dien cue chuan cua mdt sd cap oxi hoa - khir trong pin dien hoa. 3. Tinh cam, thai do Van dung kien thiie da hgc de giai thich co che hoat ddng ciia pin, acquy thudng diing trong cugc sdng hinh thanh tu duy logic cho HS. B. CHUAN B! CUA GV VA HS • GV: - Lap rap mdt sd pin dien hoa Zn - Cu, Pb - Cu, Zn - Pb theo hinh 5.3 SGK - Mdt sd tranh anh dugc ve trudc. • HS: On lai bai cii va xem trudc bai hgc 23 C. TIEN TRINH DAY - HOC Hogt dpng ciia GV Hogt dpng cua HS Hogt dpng 1 I. KHAI NIEM VE CAP OXI HOA - KHLT CUA KIM LOAI GV yeu cau HS - Viet qua trinh nhudng, nhan electron ciia cac kim loai va ion sau: Cu, Ag, Fe, Ag", Cu-", Fe-". - Cho biet vai trd ciia cac chat trong ban phan irng. GV gidi thieu: Dang oxi hoa va dang khir ciia cimg mdt nguyen td tao nen cap oxi hoa-khii' ciia kim loai: o-~ ,-^ D'ttsoxibda / Bieu dien: ^ /u,, , , .. /D'n g kho Yeu cau HS viet eac cap oxi hoa- khir cho cac nguyen td kim loai tren. GV bd sung: Ngoai cap tren cdn mdt sd cap dac biet nhu: ^^ / i, - ^ /i T /re " / rt. HS thao luan cho ket qua 4- s. * 0 Ag+ e < 1 Ag ^-. 1 + ^ N. ./ ^ 0 Cu +2e < ' Cu he +2e < ' he Chat oxi hoa Chat khir HS viet cac cap oxi hoa / khir: AgV cu^y Fe-y / A g - /Cu ' /F e Hogt dpng 2 II. PIN DIEN HOA 1. Khai niem ve pin dien hoa, suat dien dong va the dien circ GV lam thi nghiem: - Cdc 1 dung 50ml dung dich CUSO4 IM cdc 2 dung 50ml dung dich ZnS04 IM. hai cdc ndi vdi nhau bang dng chu U cd chira KNO3 liim cau ndi. - Nhiing vao cdc CUSO4 1 la Cu, cdc ZnS04 1 la Zn hai la kim loai nay dugc 24 HS quan sat thi nghiem va nhan xet: Hiin lugng: - Kim vdn ke bi lech ve phia circ Cu cd gia tri 1,10V. - Dien cue Zn bi an mdn dan. - Cd 1 ldp kim loai Cu bam len dien circ Cu. Hogt dpng ciia GV noi vdi nhau bang I day dan cd gan 1 vdn ke. Yeu cau HS quan sat va neu hien tirgng. GV bd sung: - Kim vdn ke bj lech cd nghTa la xuit hien 1 hieu dien thi giu'a hai dien cue, chirng td tren mdi cue cd 1 hieu dien the nhat dinh. - Hieu dien the giua 2 dien cue (Epjn) dugc ggi la suat dien ddng. E = E - E Hogt dgng ciia HS - Mau xanh ciia dung dich CUSO4 bi nhat dan. 2. Ctf che phat sinh dong dien trong pin dien hoa GV hudng dan HS giai thich ca chi hoat ddng ciia pin dien hoa Zn-Cu. - Giai thich hien tirgng xay ra tren moi dien cue. - Giai thich mdi lien he giua 2 dien cue. Giai thich: - Dien cue Zn bi oxi hoa: Zn —> Zn"" +2e Do vay dien circ Zn bj mdn dan. - Dien cue ddng: dung dich Cu- bi khir thanh Cu kim loai. Cu'^ +2e^C u Do vay tren cue Cu cd 1 ldp ddng bam vao va dung dich CUSO4 bi nhai mau dan. - Dien cue Zn: Zn -^ Zir' + 2e nen du electron nen mang dien tich am (dien cue am). 25 Hogt dpng cua GV Hogt dpng cda HS - Diin cue Cw:Cu-"+2e->Cu nen thilu electron mang dien tich duong (dien cue duang). => Khi ndi 2 cue vai nhau bdng mot ddy ddn thi lap tuc tgo ra su chuyen electron tic cue Zn sang cue Cu. INUU i;u t;au iiui ^^^^llua uun g uivn i-^iiv^j; trung hoa dien tich. Do dd qua trinh chuyin electron dugc thuc hien lien tuc. - Phan ling xay ra trong pin. GV yeu ciu HS kit luan ve ca che hoat ddng cua pin. GV bd sung: - Cue Zn la nai xav ra su oxi hoa nen ggi la cue anot. - Cue Cu la nai xay ra sir khir nen ggi la circ catot. Zn + Cu^" -^ Zn^^ + Cu Kit lugn: - Trong qua trinh hoat ddng cua pin co su bien ddi ve ndng do cae ion Zn , Cu^". - Ddng dien tao ra la ddng dien mgt chieu. - Suat dien dgng cua pin phu thudc vao: Ban chat kim loai, ndng do dung dich va nhiet do. HS ghi bai Hogt dpng 3 III. THE DIEN ClTC CHUA N CUA KIM LOAI GV dat van de: Gia tri hieu dien the ciia chiing ta do dugc trong thi nghiem tren la hieu ciia cac the dien cue. 26 HS thao luan va nhan xet - Khdng the do dugc gia tri tuyet ddi ciia the dien cue. Hogt dpng cua GV E = F - F '-piM c.,^, n,_ , Vay cac the dien cue dd cd gia tri bing bao nhieu? GV hudng dan HS giai quylt vin dl. GV chuyen tiep: Dien cue chuan cua hidro dugc eau tao nhu the nao? Chiing ta ciing nghien cim trong muc sau. Hogt dpng cda HS - Vi vay ngudi ta dua ra 1 the dien cue so sanh. Chip nhan quy udc the dien cue ciia nd bang 0. - Dien cue dugc chgn la dien cue hidro chuan. 1. Dien cue hidro chuan GV chieu dien cue chuan hidro len man hinh eho HS quan sat va yeu cau HS neu cau tao ciia dien cue chuan hidro. Platin dd axit / / :> ^ > > / / ^ Vay ca che hoat ddng cua dien cue hidro dien ra nhu the nao? HS quan sat va nhan xet - Gdm mdt tam platin cd phii mudi platin nhiing trong dung dich axit H IM. Khi hidro dugc thdi lien tuc dudi ap suat latm, khi hidro dugc hap phu lien tuc tren be mat tam platin. HS nghien ciiu SGK va nhan xet H,< >2W + 2e Vdi the ciia dien cue chap nhan la 0,00V d mgi nhiet do. Tire la 2H*/H , 0,00 V 2. The dien cu-c chuan cua kim loai GV cho HS nghien ciiu SGK yeu cau HS cho bilt: - Cach lip thilt bi xac dinh the dien cue chuin ciia mdt kim loai nao dd. HS nghien cim SGK va nhan xet - Thiet bi xac dinh the dien chuin cua kim loai Zn dugc lap nhu hinh ve. 27 Hoat donu ciia GV Hogt dgng ciia HS Vi ciu: Kim loai Zn Gia tri dien ke cho biet dieu gi? - Ciic phan irng xay ra trong qua trinh hoal dgng ciia pin. GV: Tirang tu hay vicl cac qua trinh xav ra trong pin xac dinh: - The dien cue chuan ciia kim loai Ag hicl 1 pm 0.80V - Vicl phan img xa)' ra trong pin dien hoa. 28 Dung dich axit cd [H ] =1M Dung dich ZnS04 cd ndng do 1M - Dien ke cho biet ddng dien chay tir cue hidro sang dien cue kem chuan va suit dien ddng eiia pin bang 0,76V. Nhu vay Zn la cue am (cue anot) => Ep,„=E„., F = E" •^'(--t ^11-/11 . • F / , /jr// n ""/ji-' Vn -0,76V - Cac phcin irng xay ra trong qua trinh xac dinh the dien cue. 2+ Tai anot (Zn): Zn—>• Zn + 2e Tai catot (Hidro): 2H " + 2e -» H2 Phan iing xay ra trong pin dien hoa la Zn + 2H " -^ Zn^" + HT HS thao luan cho ket qua: - Do Epin = + 0,80V va dien cue Ag la dien cue duang. Dien cue hidro la dien cue am. - Phan img xay ra trong pin dien hoa: Tai cue am (anot): Hogt dpng cua GV Hogt dpng cua HS H2 -> 2H" + 2e Tai cue duong (catot): Ag" + e ->Ag => 2Ag" +H2 -^ 2H " +2Ag Hogt dpng 4 IV. DAY THE DIEN CUC CHUA N CUA KIM LOAI GV cho HS nghien cuu SGK va yeu cau HS cho biet - The nao la dien cue chuan ciia kim loai. - Nguyen tac sap xep eac cap oxi hoa khu. GV chieu len man hinh day the dien cue chuan ciia kim loai cho HS quan sat va bd sung: Cap H /H2 la cap dua vao de so sanh ngoai ra cdn cd cap Fe" /Fe" nam giiia cap Cu va Ag HS nghien ciru SGK va nhan xet - Thi diin cue chudn: la gia tri cita dien circ chuan ciia kim loai so vdi dien cue hidro d 25 C, dan vi V(vdn). - Nguyin lac sdp xip: Gia trj the dien cue chuan ciia cae kim loai dugc sap xep tir thap den cao thi dugc day the dien cue chuan ciia kim loai. HS ghi bai. Hogt dpng 5 IV. Y NGHIA CUA DAY THE DIEN CUC CHUA N CUA KIM LOAI 1. So sanh tinh oxi hoa - khu GV chilu lai day the dien cue chuan ciia kim loai len man hinh eho HS quan sat va yeu ciu HS cho biet: theo chieu mui ten thi tinh oxi hoa, tinh khir bien ddi the nao? HS quan sat, thao luan va nhan xet 29 Hogt dpng cua GV Hogt dpng cua HS i3- . K' Na' Mg Al Zh Fe Ni' Sri Pb K Na Mg Al Zn Fe Ni Sn Pb H Ctr'Ag Au'' H2 Cu Ag Au Tinh oxi hoa ciia ion kim loai tang K' Na Mg' Al'" Zn* Fe' Ni " Sn' Pb' K Na Mg Al Zn Fe Ni Sn Pb IT Cu'Ag' Aif" H2CU Ag Au Tinh khir cua kim loai giam 2. Xac djnh chieu cua phan img oxi hoa - khir GV yeu cau HS so sanh tinh oxi hoa ciia ion kim loai, tinh khir ciia kim loai va the dien cue chuan ciia 2 cap oxi hoa 2+ khir: Cu /Cu, Ag /Ag. GV yeu cau HS neu chieu phan iing tir do riit ra quy tac phan img cua 2 cap the dien cue chuan. GV nhan xet va bd sung: - Quy tac a dimg de xet chieu phan img ciia cae cap oxi hoa khir. - Neu cd nhieu cap trong cimg mgt mdi trudng thi hai cap cd the dien cue chuan khac nhau nhieu nhat thi phan img trudc. 30 HS thao luan cho ket qua: - Ion Ag cd tinh oxi hoa manh hon ion Cu^" - Kim loai Cu ed tinh khir manh hon kim loai Ag. Thi dien cue chuan: E° > E" Ag'/Ag Cii'"/Cu =:> Chieu xay ra phan ling giira 2 cap oxi hoa khir Cu + 2Ag" ^ Cu^" + 2Ag HS Phan ring xay ra theo quy tac anpha (a). n 2+ Cu Ag" Cu Ag 2+ 2Ag +Cu->Cu +2Ag Hogt dpng cua GV GV chieu bai tap sau len man hinh cho HS thao luan: Khi cho hdn hgp Mg, Zn vao dung dich chiia cae mudi Cu(N03)2, AgNOa. Neu thir tu eac phan irng xay ra trong dung dich. GV nhan xet ket qua HS trinh bay va yeu cau HS dua vao da thi dien cue chuan hay cho biet ion H " trong dung dich cd the oxi hoa dugc nhirng kim loai nao? Hogt dpng cua HS HS quan sat va thao luan cho ket qua Thii tu the dien cue chuan ciia cdc kim loai trong day difn hoa Mg-'Zri'Cu'Aj " Mg Zn Cu Ag (Gia tri the dien cue chuin tang din) Nen Mg tac dung vdi AgNOs trudc Mg +2Ag" -^ Mg^" +2Ag - Neu Mg hit thi Cu tac dung vdi AgNOs Zn +2Ag" ->Zn^" +2Ag Sau dd ed the cd phan iing neu Ag het Zn + Cu 2+ Zn^" + Cu -NeuAg het thi Mg tac dung vdd Cu Mg + Cu^" -> Mg^" + Cu Sau dd cd the cd phan iing neu Mg het Zn + Cu^" -^ Zn^" + Cu HS nhan xet: Nhirng kim loai cd the dien cue chuan am thi bi ion H oxi hoa. Vi du: Zn cd E" ,, Zn • / Zn 0,76V 2+ Zn + 2H -^ Zh 3. Xac djnh suat dien dong chuan cua pin dien hoa H2 GV dat vin de: Lam the nao de xac dinh thi suit dien dgng chuan ciia pin HS thao luan va nhan xet Ta cd (+1 "(-) 31 Hogt dpng ciia GV dien hoii khi biet the dien cue chuan ciia cap oxi hoa khu cua dien cure am va dien civc duang. Tir dd xac dinh suat dien ddng chuan ciia cap pin Zn-Cu. Hogt dpng cua HS E(c6 the bchirn) '"•ay Ep„, = E(c6 ihC lan) - Vidu: E" , =-0,76V Zn" / / n E" ,.„, =0.34V ^ F • =F° - F" Zn-' /Zn ^ "^-pin '^cu='/Cu ^ ? = 0,34V-(-0,76V) = 1,1V 4. Xac djnh the dien cue chuan ciia cap oxi hoa - khir GV dat van de tiep: Lam the nao de xac dinh the dien cue chuan ciia cap oxi hoa khir khi biet suat dien dgng ciia pin dien hoa vii the dien cue chuan ciia cap oxi hoa - khu cdn lai. Tir do xac dinh the dien cue chuan ciia cap Ni- /Ni biet Epjn Ni-CLi= 0,60V va E" „ , =0,34V. HS thao luan va nhan xet Ta cd E = E,., -E, ^pm - t-( + ) (-) Trudc het phai xet cap oxi hoa khir can xac dinh the ddng vai trd la cue am hay cue duang trong pin. Sau dd tir cdng thiic Ep|„ = E,^| -E|_jtinh dugc the dien circ chuan ciia cap oxi hoa - khir can xac dinh. Vi du: Epin Ni-Cu= 0,60V ta thay Ni hoat ddng han Cu nen Ni ddng vai tro la circ am, Cu ddng vai trd la cue duang. (-) ( + ) pin > E" , = E \ Ni' /Ni Cir /CM •E° p)n = 0,34V - 0,6V =-0,26V Hogt dpng 6 CUNG CO BAI V A BAI TAP VE NH A GV chieu eac bai tap sau len man hinh cho HS thao luan cung cd ndi dung bai hoc: 32 HS quan sat theo luan eho kit qua Hogt dpng cua GV Bai 1. Biet suit dien ddng chuin ciia pin Zn-Cu la +1,10 vdn, thi dien cue chuan ciia dien cue Zn la -0,76 vdn, thi dien cue chuin cua dien cue Cu la A. + 0,34 vdn B. - 0,34 vdn C.-1,86 vdn D.+1,86 vdn Bai 2. Trong day thi dien cue chuin cua kim loai, vi tri mdt sd cap oxi hoa - khir dugc sip xIp nhu sau: A1^"/A1, Fe-"/Fe, Ni2"/Ni, Cu'"/Cu, Fe^"/Fe2", Ag"/Ag, Hg^"/Hg. Trong sd eac kim loai Al, Fe, Ni, Cu, Ag, Hg thi cd bao nhieu kim loai khi tac dung vdi dung dich mudi Fe " chi khir duac Fe^" vl Fe'"? Hogt dpng cua HS Bai 1. Chgn dap an A Bai 2. Chgn dap an D A. 2 C. 1 B.4 D. 3 Bai tap ve nha: 1, 2, 3, 4, 5, 6, 7, 8 (SGK) D. HU'ONG DAN GIAI BAI TAP TRONG SGK 1. Chgn dap an A Chgn dap an C Ti,'t •' A'- .' u u ' Ag" Cu'" Al'" Mg' I hu tu giam dan tinh oxi hoa: —^ * Na" Ag ' Cu ' Al ' Mg ' Na 2+ 2+ a) Cap Pb /Pb va Fe /Fe thi Pb la cue duong cdn Fe la cue am Phan img hoa hgc Fe + Pb^" -^ Fe'" + Pb b) Cap Ag"/Ag va Fe "/Fe thi Ag la cue duang cdn Fe la cue am Phan ling hoa hgc Fe + 2Ag'' Fe'" +2Ag 3- TKBG HOA HQC 12 NC-T2 c) Cap Ag"/Ag va Pb'"/Pb thi Pb la cue am cdn Ag la cue duong Phan irng hoa hoc Pb + 2Ag" -» Pb " + 2Ag 5. Chgn dap an C 7. Trong phan img Fe + Ni ^- Fe + Ni a) Fe la cue am cdn Ni la cue duong 2+ b)dcucam: Fe —> Fe + 2e d cue duong: Ni + 2e ^-N i c) Epi, -El^,^,-K,'.. =-0,26V-(-0,44V) = 0,18V 8. Trong pin Cr-Ni thi Cr la cue am nen E - F - F ^ F " -F " -E ° =-026 V - 0 51 V = - 0 77V Trong pin Cd-Mn thi Mn la cue duong nen: t'( + ) Ep,„ -+-E,^) ^ E" */M n E ; , + El^,, ^^^ = 0,79V + (-0,4)V = 0,39V "-^ ^Mn ^ E, . TU" LIEU THAM KHAO The dien cvrc 1. • Khi nhiing mdt thanh kim loai M vao dung dich mudi ciia nd (M " ), ta dugc mdt dien cue. Neu ndng do (chinh xac hon phai la hoat do) cua dung dich ion M la 1M d 25 C thi ta cd the dien cue chuan E ciia cap oxi hoa - khir M " / M (theo quy udc viet dang oxi hoa/dang khu). Hai trudng hgp cd the xay ra: - Neu thanh kim loai de nhudng electron (M -> M" " + ne), ion M" " tao ra se dugc phan tan vao dung dich, electron d lai tren thanh kim loai M lam eho thanh kim loai tich dien am va cd mdt dien thi am so vdi dung dich -^ E°„. <0. - Neu M" trong dung dich de nhan electron (M" " + ne ^ M ) thi nd se nhan electron ciia thanh kim loai M lam cho thanh kim loai tich dien duong va cd mdt dien the duong so vdi dung dich -> E° „, > 0 34 Tuong tu nhu vay, ngudi ta cd thi tao ra cae dien cue khi bing each dimg mgt thanh kim loai tra (Pt) hay thanh than chi tilp xuc ddng thdi vdi khf va nhiing trong dung djch chira ion ciia khi dd. Vi du: dien cue hidro H2(k) (Pt)/H"(dd), dien cue oxi 02(k) (Pt)/OH/dd), dien cue clo Cl2(k) (Pt)/Cr (dd), ... Ddi vdi nhung cap oxi hoa khir trong dd khdng cd dan chit, ngudi ta diing dien cue gdm thanh kim loai tra (Pt) hay thanh than ehi nhung trong dung djch chiia dong thdi dang oxi hoa va dang khii-, ching han nhu dien cue Fe^"(dd)/Fe'"(dd) (Pt), dien cue Sn^"(dd)/Sn'"(dd) (Pt), ... H, (1dm)" dd l,On Lo thoat khi H, Hinh 5.3. Dien cue hidro tieu chuan Ngudi ta khdng xac dinh dugc gia tri tuyet ddi cua thi dien cue nhung do dugc hieu dien thi ciia 2 dien cue (suit dien ddng ciia pin). Vi vay, dl so sanh the cua 2 dien cue khac nhau, ngudi ta xac dinh thi ciia dien cue dd so vdi dien cue hidro chuin, vdi quy udc E°.^ = 0,00V. Bing each dd cho 2 r"i / H 2 ^^ phep ta xac dinh dugc the dien cue chuan ciia nhilu cap oxi hoa khir M""/M va lap thanh bang tra ciiu (xem bang 5.1). Theo quy udc cua lUPAC, thi dien cue chuan eiia cac cap oxi hoa khir dugc vilt cho qua trinh khir: Oxh + ne -> Kh Trong dd: Oxh - dang oxi hoa; Kh - dang khir lien hgp cua mdt cap oxi hoa - khir. 35 Thi dien cipc chuan cua mot sd cap oxi hoa/khir ^(V) -3,04 -2,92 -2,92 -2,90 -2,89 -2,87 -2,71 -2,37 -2,25 -1,85 -1,66 -1,63 -1,18 -0,83 -0,76 -0,74 -0,48 -0,44 -0,41 -0,40 -0,28 -0,25 -0,20 -0,14 -0,13 -0,04 0,00 36 Qua trinh khCr Li* + e -> Li K" + e ^ K Rb* + e ^ Rb Ba^"+2e^B a Sr^"+2e->Sr Ca^"+2e^C a Na" + 1e -» Na Mg^" + 2e ^ Mg H2 + 2e ^> 2H Be^" + 2e -> Be Al^* + 3e ^ Al Ti'" + 2e ^ Ti Mn'"+2e^.M n 2H2O + 2e ^ H2 + 20H Zn'" + 2e -> Zn Cr^" + 3e -^ Cr S + 2e ^ . S'- Fe'" + 2e ^ Fe Cr^" + 1e^Cr^ " Cd^" + 2e -^. Cd Co'" + 2e ^ Co Ni'" + 2e ^ Ni Mo^" + 3e ^ Mo Sn'" + 2e -> Sn Pb'"+2e^P b Fe^" + 3e ^ Fe 2H" + 2e^H 2 Oxh/Kh Li'/Li K"/K Rb"/Rb Ba'"/Ba Sr'"/Sr Ca'"/Ca Na"/Na Mg'"/Mg H2/2H Be'"/Be AI^"/AI Ti'"/Ti Mn'"/Mn H2O/OH Zn'"/Zn Cr^"/Cr s/s'- Fe'"/Fe Cr^"/Cr'" Cd^"/Cd Co'"/Co Ni'"/Ni Mo^"/Mo Sn'"/ Sn Pb'"/ Pb Fe^"/ Fe 2H"/ H2 Qu^ trinh khCr P + 3H" +3e ^ PH3 S + 2H" + 2e -^ H2S Sn"" + 2e -> Sn'" Cu'"+ 1e->Cu" SOf +4H"+2e-^H2S03 Cu'" + 2e -^ Cu Fe(CN)=-+1e-> Fe(CN)^- Cu"+1e->Cu I2 + 2e ^ 2 r MnO, + 1e ^ MnO^" O2 + 2H" + 2e ^ H2O2 Fe'"+1e^Fe' " Hg^' + 2e^2H g Ag"+ 1e ^ Ag 2Hg'" + 2e ^ Hg^' N03 + 3H" + 2e^HN0 2 + H20 Pd'" + 2e -^ Pd HN02 + H" + le^N O + HjO Br2 + 2e ^ 2Br" O2 + 4H" + 4e ^ . 2H2O 2HNO2 + 4H" + 4e^ N2O + 3H2O CI2 + 2e ^ 2Cr Pb02 + 4H" + 2e -> Pb'" + 2H2O Au^" + 3e ^ Au MnO, + 8H" + 5e ^ Mn'" + 4H2O MnO, + 4H" + 3e ^ MnOs + 2H2O Ag'"+ le^Ag " F2 + 2e -> 2F Oxh/Kh P/PH3 S/H2S Sn""/ Sn'" Cu'"/ Cu" SO4'-/ H2SO3 Cu'"/ Cu Fe(CN)^-/ Fe(CN)g^- Cu"/Cu 12/21- MnO^/ MnO^ O2/H2O2 Fe^"/Fe'" Hgr/2Hg Ag"/ Ag 2Hg'"/ Hg^^ NO3/HNO2 Pd'"/ Pd HNO2/ NO Br2/2Br O2/2H2O 2HNO2/ N2O Cl2/2Cr Pb02/ Pb'" Au^"/Au MnO,/Mn'" MnO, / Mn02 Ag'"/Ag" F2/2F E°(V) +0,06 +0,14 +0,15 +0,15 +0,17 +0,34 +0,36 +0,52 +0,54 +0,57 +0,68 +0,77 +0,79 +0,80 +0,92 +0,94 +0,99 + 1,00 +1,06 + 1,23 + 1,29 + 1,36 + 1,45 + 1,50 +1,51 + 1,69 +1,98 +2,87 1 Nhdn xel: - Thi dien cue chuan E trong bang la \'iet cho qua trinh khir: Oxh + ne -> Kh do dd khi viet cho qua trinh oxi hoa: Kh -^ Oxh + ne thi phai ddi dau E . Vi du: K" + e ^ K K ^ K" + e E" E" -2,92V +2,92V - Gia tri thi dien cue danh gia kha nang oxi hoa - khir ciia dang oxi hoa va dang khir: E" cang duang thi dang oxi hoa cang manh va dang khir cang ylu, ngugc lai, E" cang am thi dang oxi hoa cang yeu va dang khir cang manh. Day la nguyen tac xep day dien hoa kim loai. Vi du: Trong bang nay Li la chit khir manh nhat va F2 la chat oxi hoa manh nhat. - The dien cue la mdt dai lugng cudng do, khi thay ddi he sd ti lugng ciia mot nira phan img, gia tri eiia the dien cue chuan EO khdng thay ddi. Vi du: Ag" + e ^ Ag E" = +0,80V 3Ag" + 3e -^ 3Ag E° = +0,80V - The dien cue cdn phu thudc vao nhiet do va ndng do cua chat oxi hoa va chat khir theo phucmg trinh Nemst: a Oxh + ne ^ P Kh 0 303RT [Oxhf E = E° + - IgV- ^ (5.1) Phuang trinh (5.1) ggi la phuong trinh Nernst eho thi dien cue. Trong do: E - the dien circ d nhiet do T vdi ndng do dang xet E - the dien cue chuan (25 C, 1M) n - sd electron trao ddi d dien cue [Oxh] - ndng do mol ciia dang oxi hoa [Kh] - ndng do mol cua dang khir 38 a - he sd hgp thire cua dang oxi hoa (3 - he sd hgp thiic ciia dang khir R-hin g sd khi (8,31451 OJ.K'Vmor') F - hing so Faraday (96485,309C. mol"'). O 25 C cdng thire (5.1) dugc vilt ggn: E = E" 0,059 [Oxh]" n ^ [Khf (5.2) Ap dung eho eac qua trinh khir sau d 25"C: a) MnO; + 8H" + 5e ^ Mn'" + 4H,0 j^^go^O ^ jg[K4nO,-][H"]« n ^ [Mn'"] b) M"" + ne ^ M . g^^o^O ^ lg[M""] n Vi du: Xac dinh the dien cue Sn" /Sn va Pb /Pb d 25 C neu ndng do mol eiia ion Sn va Pb- lan lugt la 1,2M va 0,1M. Bai giai: Tir sd lieu bang tren ta ed: E° =-0]4V - E" =-013 V Ap dung phuang trinh Nemst eho hai trudng hgp tren ta ed: Dien cue Sn-"/Sn: E = E° +-^^lg[Sn'" ] =-0,14V 9 2+,^. „ .,« 0,059, Dien cue Pb^"/Pb: E = E" +- lg[Pb'"] = -0,16V 2. Pin dien 2.1. Khdi niim Pin la mdt he gdm 2 dien cue ed the khac nhau dugc ghep lai vdi nhau va hoat dgng theo nguyen tac bien nang lugng eiia phan irng hoa hgc (thudng la phan iinii oxi hoa khii) thanh nang lugng ddng dien. 39 Quy udc viet so dd pin cua lUPAC: - Dien cue cd the E ldn hon lam dien cue ben phai (cue duang) va d dd xay ra qua trinh khir. - Dien cue cd the E nhd han lam dien cue ben trai (cue am) va d dd xay ra qua trinh oxi hoa. Vi du, so do pin Danien-Jacobi dugc vilt nhu sau: Zn| ZnSO, (C) || CuSO, (C)| Cu (5.3) §iOn cue b^n tr i (CucOm) §iOn ciic b^n phai (Cue d-dng) Quy udc eac ki hieu trong sa dd pin nhu sau: - Vach thang dimg | chi ranh gidi hai pha: pha ran kim loai va pha ldng dung dich. - Hai vach thang dimg || chi ranh gidi hai pha ldng ma hai pha ldng dd lien he vdi nhau bang mdt eau mudi lam eau ndi (xem hinh 5.2). - Chir C chi ndng do dung dich mudi dugc diing trong pin Q Cau noi KCl so,: Zn^ Cu^ ® tt(^ + + + + Zn" sof Cu' SO,: So" d6 hoat dong cua pin Oanlen-Jacobi 2.2. Hogt dpng cua pin • Dien cue ben trai (-): xay ra qua trinh oxi hoa Zn -> Zn^"+ 2e, do dd ndng do ion Zn tang len va dugc trung hoa bdi ion gdc axit SO^'" ed du d dien cue ddng. Cae electron se di chuyin qua dien cue ddng theo day dan. • Dien cue ben phai (+): xay ra qua trinh khir Cu^" + 2e ^ Cu, do dd se xuit hien ket tua Cu bam tren thanh ddng. => Ket qua xay ra phan iing oxi hoa - khir trong pin: Zn + Cu^" ^ Zn^" CuJ- (*.) 40 dong thdi cd sir di chuyin electron tir Zn, qua day dan. din Cu, nghia la cd su xuat hien ddng dien theo chilu ngugc lai, chilu quy udc, tir Cu sang Zn. Vay ddi vdi mach ngoai Cu la dien cue duang (ed E" ldn han) va Zn la dien cue am (cd E " be han). Chit y: 1. Neu xet mach trong ciia pin (dung dich chit dien li) thi Cu la dien cue am (catot) vi d day xay ra qua trinli khu: Cu^" + 2e -> Cu. Tuang tu Zn la dien cue duang^(anot) ddi vdi mach trong vi a day xay ra qua trinh oxi hoa: Zn -^ Zn + 2e. 2. Phan ling (*) trong pin xay ra tuang tu nhu khi cho Zn true tilp tan trong dung dich CUSO4. Song dilm khac nhau la d chd khi cho Zn true tilp vao dung dich CUSO4 thi nang lugng cua phan img dugc giai phdng dudi dang nhiet (lam ndng binh phan ung), cdn trong pin nang luang duac giai phong dudi dang dien nang (pin da tao ra ddng dien). 3. Cau ndi (KCl) d trong pin cd 2 nhiem vu: lam kin mach dien bing cac ion djch chuyen tir mia phan iing nay sang nua phan irng kia va giu eho dung dich mudi ludn dugc trung hoa dien. 2.3. Suat diin dpng cda pin (sdd) Sdd ciia pin la thudc do khuynh hudng thue hien phan img hoa hgc trong pin (hay cdn ggi la the cua phan iing oxi hoa - khir xay ra trong pin): Epin = Ef-Et = E+-E_ (5.4) • 0 dieu kien chuin (nong do eac chit Imol.f' va d nhiet do 25"C) ed thi thay E bang E° trong cdng thire (5.4). Vi du xet pin Zn-Cu ta cd: E:=E?-E : = E°,.^^„-E°„.,^„=0,34-(-0,76 ) = 1,1V • 0 dieu kien khdng chuin: Ef, Et dugc tinh theo phuang trinh Nernst ciia thi dien cue (cdng thirc 5.1 hoac 5.2 nlu d 25"C) khi do ta thu dugc phuang trinh Nemst ciia sdd: Xet phan irng oxi hoa khir xay ra trong pin: aA + bB + ... ^ cC + dD + ... O 25 C phuang trinh Nernst cd dang: 41 _po ^0 ^ [ATK.. . ^5 5^ '"" ^''" n ^[C^Df... Vi du: Tinh sdd ciia pin Danien-.Iacobi neu [Zn ] - IM va [Cu ] 10Md25"c. Ap dung (5.5) eho phan iing: Zn + Cu -> Zn + Cu Ep,n= 1,1+ ^^lgl O -1,13V ' n Chit y: v l mat nhiet ddng, cac phan irng hoa hgc ndi chung trong do co phan img oxi hoa - khii- chi cd thi tu diln biln (xay ra) khi cd sir giam nang lugng tir do Gibbs: AG = AH-TAS<0 Trong phan img oxi hoa khir cdn ed mdi quan he true tilp giira suat dien dong ciia pin (hay thi ciia phan irng oxi hoa - khir xay ra trong pin) va sir biln thien nang lugng tu do Gibbs (AG) ciia phan img dd theo cong thire sau: AG = -nFE (5.6) (n la sd e trao ddi, E = Epin = Epu) Khi dd: - Phan img tu xay ra AG < 0 -» E > 0 - Phan irng theo chilu nghich AG > 0 -^ E < 0 - Phan irng dat trang thai can bang AG = 0 -^ E = 0 Bai 21. LUYEN TAP TlNH CHAT CU A KIM LOAI A. MUCTIEUBAI HOC 1. Kiln thiFC HS cung c6 kien thirc vi: • Tinh chit vat li va hoa hgc chung ciia kim loai. 42 • Cap oxi hoa - khu- ciia kim loai. • Pin dien hoa (the dien cue chuin cua kim loai, suit dien dgng chuin ciia pin dien hoa). HS hiiu: Giai thich dugc nguyen nhan gay ra cac tinh chit vat li chung va tinh chit hoa hgc dac trung eiia kim loai. 2. KT nang Ren luyen cdc kindng: • Biet xac dinh ten va diu ciia eac dien cue trong pin dien hoa. • Tinh suat dien ddng chuin ciia pin dien hoa. B. CHUAN B! CUA GV VA HS • GV: - May tinh, may chilu, eac philu hgc tap. - He thdng bai tap dn tap, he thdng tinh chit hoa hgc ciia kim loai. • HS: On tap cac bai da hgc va xem trudc bai luyen tap. C. TltN TRJNH DAY - HOC Hogt dpng ciia GV Hogt dpng CUO HS I. KIEN THUC CO BAN CAN NH O GV Chia HS thanh 4- 5 nhdm sau dd giao cae ndi dung cho HS thao luan dudi su dieu khiln cua GV HS chia thanh eac nhdm. Hogt dpng 1 1. Tinh chat chung ciia kim loai Nhdm I: Neu tinh chit chung ciia kim loai giai thich tai sao kim loai ed tinh chat do Nhdm 1 thao luan cho kit qua a) Tinh chdt vgt li: Kim loai cd tinh deo, tinh dan dien, tinh dan nhiet va anh kim.... Tinh chat vat li chung ciia kim loai gay nen bdi su cd mat cua cae electron tu do cd mat trong tinh thi kim loai. 43 Hogt dpng cda GV Hogt dpng cda HS b) Tinh chdt hod hgc: Kim loai ed tinh chat chung la tinh khir M >M""+ne Kim loai cd tinh khir la do nguyen tir kim loai thudng cd 1-3 electron d ldp ngoai eiing nen cd xu hudng cho electron de dat dugc cau hinh ben ciia khi hiem. Kim loai tac dung dugc nhieu chat oxi hoa nhu: Phi kim, axit, mudi, nude... 2. Cap oxi hoa khir - cua kim loai Nhdm 2: Cap oxi hoa-khir la gi? Cach bieu dien cap oxi hoa khir. Cho biet chieu phan irng giua 2 cap oxi hoa khir ciia kim loai. Cho vi du minh hoa. 44 Nhdm 2 thao luan eho ket qua Cap oxi hod khic la dang oxi hoa va dang khir cua cimg mdt nguyen td tao nen cap oxi hoa-khir ciia kim loai: Bilu diln: D'ng oxi hda / /D'n g kho V! dir Ag / Cu""/ _ Fc-^" _., ^'- /Ag ' /Cu ' /Fe- " Hai cap oxi hoa khir dugc sap xep theo chieu tang dan the dien cue. Cac cap oxi hoa khir ciia kim loai phan iing theo quy tac a (anpha). Vidu: Cu^"/ ,Ag" / / Cu /A g Theo quy tac a ta ed chieu phan img. + Cu-^ r---- Ac", fii—-^"" ' ""'' ,\u Phan irng li^j hgc 2+ 2Ag +Cu -> Cu +2A Hogt dpng cua GV Hogt dpng cua HS 3. Pin dien hoa Nhdm 3: Pin dien hoa la gi? Cac phan img xay ra trong pin dien hoa. Cho vi du minh hoa. Nhdm 3 thao luan cho ket qua: - Pin dien hoa la thiet bi trong dd nang lugng cua phan iing oxi hoa khir chuyin thanh dien nang. - Pin dien hoa dugc tao bdi hai cap oxi hoa khir trong dd. - O cue am xay ra sir oxi hoa chit khir. - O cue duong xay ra su khir chit oxi hoa. -r/fi'«.-2eapCu V ,Ag" / ^ /Cu ' /A g + 6 cue am: Cu ^ Cu^" + 2e + O cue duong: Ag + e -> Ag - Phan irng hoa hoc xay ra trong pin 2Ag" + Cu - 4. Day the dien cu-c chuan ciia kim loai Cu^" + 2Ag Nhdm 4: Neu dac diem ciia dien cue chuan hidro, liy hai cap oxi hoa - khir mdt cap cd the dien cue am, mgt cap cd the dien cue duong. Cach xac dinh thi dien cue chuan eiia kim loai. Nhdm 4 thao luan cho kit qua - Dien cue hidro chuan ed thi di^n cue quy udc bang 0,00V. - Dien cue chuan cua kim loai la dien cue bang kim loai nhiing vao dung dich mudi cua kim loai dd ed ndng do 1M d 25°C. - Cap oxi hoa khii cua kim loai cd thi dien cue am la cac cap dung trudc cap 45 Hogt dpng cua GV GV nhan xet ket qua thao luan cua eac nhdm de cac nhdm khac tu rut kinh nghiem cho ban than. Hogt Hogt dpng cda HS - Cap oxi hoa khir eiia kim loai ed the dien cue duong la cae cap dung sau cap ^ V T hoat dgng hon hidro nhu Cu^"/ Ag" / /Cu ' /A g - De xac dinh the dien cue chuan ciia kim loai ngudi ta do suat dien ddng ciia pin cd cau tao gdm dien cue kim loai can xac dinh vdi dien cue hidro. => The dien cue chuan ciia kim loai. Ep,„=E,,,-E,_, (Epin>0) dpng 2 II. BAI TAP GV chieu cac bai tap trong SGK len man hinh cho HS thao luan: Cau 1: a) Phan irng hoa hgc xay ra trong pin dien hoa la: 2Cr + 3Cu^" -^ 2Cr^" + 3Cu E eiia pin dien hoa la: A. 0,40 V B. 1,08 V C. 1,25 V D. 2,5 V Bilt EV. ^ =+0,34V Cir /Cl! EV, ^ =-0,74V Cr /Cu b) Phan img hoa hgc xay ra trong pin dien hoa: 46 HS chuan bi giai cac bai tap 1. a) Chgn dap an B b) Chgn dap an C Hogt dpng cua GV 2Au 3+ .2+ + 3Ni -> 2Au + 3Ni E ciia pin dien hoa la: A. 3,75 V B. 2,25 V C. 1,76 V D. ],25V Cau 2: a) Chat nao sau day cd thi oxi hoa Zn thanh Zn^"? A. Fe B. Ag" C. Al^" D. Ca^" b) Kim loai Zn cd the khir dugc ion nao sau day? A. Na" B. H " C. Ca^" D. Mg^" Can 3. Trong qua trinh pin dien hoa Zn - Ag hoat ddng, ta nhan thiy. A. Khdi lugng eiia dien cue Zn tang. B. Khdi lugng eiia dien cue Ag giam. C. Ndng do ciia ion Zn^" trong dung dich tang. D. Ndng do cua ion Ag" trong dung dich tang. Cau 5. Khi nhiing mdt la Zn vao dung djch mudi Co " thi thiy cd mdt ldp kim loai Co phu ngoai la kem. Khi nhiing la Pb vao dung dich mudi tren thi khdng thay hien tugng nao xay ra. a) Kim loai nao ed tinh khir manh nhat trong ba kim loai tren? Hogt dpng cua HS 2. a) Chgn dap an B b) Chgn dap an B 3. Chgn dap an C 5. a) Kim loai Zn 47 Hogt dpng ciia GV b) Cation nao cd tinh oxi hoa manh nhat trong ba cation kim loai tren? c) Sap xep eac cap oxi hoa - khir ciia nhirng kim loai tren theo chilu tinh oxi hoa ciia cation tang dan. d) Viet phuong trinh hoa hgc ciia phan irng xay ra giua cac cap oxi hoa - khir. Cau 6. Hay giai thich hien tugng thi nghiem: Ngam mdt la Zn nhd, tinh khiet trong dung dich HCl thay bgt khi H2 thoat ra it va cham. Neu nhd them vai gigt dung dich CUSO4 thiy bgt khi H2 thoat ra rat nhieu va nhanh hon. Cau 7. Cho cac cap oxi hoa - khir sau: Ag"/Ag; Fe-"/Fe; Zn-"/Zn. a) Hay viet phuang trinh eiia cac phan irng chuyen ddi giira cation kim loai va nguyen tir kim loai trong moi cap. b) Hay eho biet trong cac cap oxi hoa khii' da eho, chat nao cd tinh: - Oxi hoa manh nhat. - Oxi hoa yeu nhat. - Khii' manh nhat. - Khii' yeu nhat. Cau 8. Hay tinh the dien cue chuin cua cap oxi hoa khir E° ,, .Bilt rins /n /Zn & Epm(/„-.cu)=llOVva 48 Hogt dpng cda HS 2+ b) Cation Pb c) Zn^"/Zn, Co^"/Co, Pb-"/Pb d) HS viet phucmg trinh hoa hgc 6. Khi ngam Zn trong axit thi kem khir ion hidro cham. phan img se xay ra nhanh hon neu them vao vai gipt CUSO4 vi Zn + CUSO4 -^ ZnS04 + Cu Cu tao ra bam len thanh kem tao thanh 2 cue xay ra an mdn dien hoa. 7. a) HS tu vilt. b) Ag cd tinh oxi hoa manh nhit Zn cd tinh oxi hoa ylu nhit Zn cd tinh khir manh nhit. Ag cd tinh khir yeu nhit 8. E°(Zn^"/Zn) = +0,34V - 1,10V = -0,76V Hogt dpng cda GV E;,.,^^, =+0,34V Cau 9. Cd nhung pin dien hoa dugc tao thanh tir nhimg cap oxi - hoa khir sau: a) Pb^"/Pb va Fe^"/Fe b) Ag"/Ag va Fe^"/Fe c) Ag"/Ag va Pb^"/Pb Hay tinh suit dien dgng chuin ciia moi pin dien hoa. Bilt ring EV,^ =+0,80V " Ag /Ag ' E;^^.P,=-0,13V E:,.,,=-0,44 V Cau 10. Cd nhirng pin dien hoa dugc ghep bdi cac cap oxi hoa-khu chuin sau: a) Pb^"/Pb va Zn-"/Zn 2+ 2+1 b) Cu" 7Cu va Hg^ 7Hg c) Mg^"/Mg va Pb^"/Pb - Xac dinh dien cue duang va dien cue am ciia moi pin dien hoa. - Viet phuang trinh hoa hgc ciia phan img xay ra d cac dien cue cua mdi pin va phuang trinh hoa hgc dang ion thu ggn cua moi pin dien hoa khi phdng dien. - Xac dinh suat dien dgng chuan cua cac pin dien hoa. Hogt dpng cda HS 9. a) E° cua pin Fe-Pb = -0,13V - (-0,44V) = +0,31V b) E cua pin Fe-Ag = +0,80V - (-0,44V) = +1,24V e) E cua pin Pb-Ag = +0,80V-(-l,3V) = +2,lV 10. a) Zn la cue am eon Pb la cue duong. Pb + Cu^" ^ Pb^" + Cu b) Cu la cue am cdn Ag la cue duang. Cu + 2Ag" -^ Cu^" + 2Ag c) Mg la cue am va Pb la cue duong. Mg + Pb 2+ Mg^" + Pb 4-TKBGHOAH9C12NC-TJ 49 63122.81/DIEN PHAN A. MUC TIEU BAI HOC 1. Kiln thiHC HS biit: • Khai niem ve sir dien phan, cac trudng hgp dien phan chit dien li ndng chay va dung dich nude cua chat dien li. • Ung dung eiia sir dien phan. HS hiiu: • Nhirng phan img oxi hoa - khir xay ra d cac dien cue trong qua trinh dien phan va viet dugc phuang trinh dien phan. • Sir dich chuyen eiia eac ion trong qua trinh dien phan: Mudi NaCl ndng chay, dung dich CUSO4 vdi dien cue tra (anot tra) va dien cue tan (anot tan). 2. KT nang • Thue hien mdt sd thi nghiem dien phan don gian: Dien phan dung dich CUSO4 vdi anot tra (graphit) va anot tan (ddng). • Biet xac dinh ten cua cac dien cue trong binh dien phan. • Viet dugc phuang trinh hoa hgc eiia phan img xay ra tren cac dien cue va viet dugc phuong trinh dien phan. • Giai dugc cae bai toan lien quan din sir dien phan. B. CHUA N B! CUA GV VA HS • GV: Hoa chat, dung cu (eho thi nghiem dien phan dung dich CUSO4 vdi cac dien cue graphit va dien cue ddng). - Hoa chit: Dung dich CUSO4 0,5M - Dung cu: + Ong hinh chii U. + Niit cac dien cue. + Ngudn dien mdt chieu cimg vdi biln trd. + Day ndi eac dien cue. • HS: dn tap kiln thirc ve pin dien hoa va day thi dien cue ciia kim loai. 50 C. TlgNTRlNHDAY-HOC Hogt dpng cua GV Hogt dpng cua HS Hogt dpng 1 I. KHAI NIEM 1. Thi du GV Cho HS quan sat sa dd hinh 5.10 SGK, yeu ciu HS md ta binh dien phan, hoat ddng cua binh dien phan. GV luu y HS: Can phan biet cue ciia pin dien hoa va cue ciia binh dien phan. - Trong pin: Cue am la cue anot, cue duong la cue catot. - Trong binh dien phdn: Cue am la cue catot, cue am la cue anot. Ndi chung: Co chi hoat ddng cua pin va binh dien phan la hai qua trinh ngugc nhau (pin hoat dgng phat sinh ddng dien cdn binh dien phan hoat ddng nhd ddng dien). HS nghien cim SGK va nhan xet - Thiit bi dien phdn gdm cd: + Binh dien phan. + Hai dien cue: Cue am va cue duong; andt dugc ndi vdi cue (+) ciia ngudn dien mdt chieu catot dugc ndi vdi cue (-) cua ngudn dien mdt chieu. - Hogt ddng ciia binh diin phdn: Khi cd ddng dien mdt chieu chay qua tren dien cue duong (anot) xay ra su oxi hoa, tren dien cue am (catot) xay ra su khir. 51 Hogt dpng cua GV Hogt dpng cua HS 2. Khai niem GV cho HS nghien ciiu thi du trong SGK va yeu cau HS riit ra khai niem sir dien phan. HS nghien cuu SGK va nhan xet Su dien phdn la qua trinh oxi hoa - khir xay ra tren be mat cac dien cue khi cho ddng dien mdt chieu di qua chat dien phan (hgp chat ndng chay hoac dung dich dien li). Hogt dpng 2 II. Sir DIEN PHAN CAC CHA T DIEN LI 1. Dien phan chat dien li nong chay GV yeu cau HS neu cac budc tdng quat de dien phan ndng chay mdt chat, tir dd viet qua trinh xay ra khi dien phan ndng chay NaCl. GV nhan xet va bd sung: Cd nhieu chat can dien phan ndng chay nhu mudi cua kim loai kiem, kiem thd, oxit nhdm.... 52 HS thao luan eho ket qua: - Khi dun chay thi chat dien li se phan li thanh cac ion. Sau dd cac ion phan li ve dien cue - Tai cac dien cue xay ra qua trinh oxi hoa va qua trinh khir cac ion tai cac dien cue. - Cdng cac 2 qua trinh d hai dien cue (sao cho tdng electron bang tdng electron nhan) thu dugc phuang trinh dien phan. So do diin phdn ndng chay NaCl XX NaCI —»> Na" + Cl" Catot (cue am) Anot (cue duong) Na" +e-^N a 2Cr-»- CI2 +2e Phuang trinh dien phdn 2NaCl """^ ) 2 Na + CI2 Hogt dpng cua GV Hogt dpng cda HS 2. Dien phan dung djch chat dien li trong nuo'c a) Dien phdn dung dich CUSO4 v&i cdc diin cue tra (graphit) GV gidi thieu: Thii tu dien phan cac chat d cae dien cue Tgi catot: Xay ra qua trinh khir cae cation theo thii tu Thir tir dien phan tai catot JC^ Na Mg' Al'' Zn' Fe* Nj"' Sn' Pb' K Na Mg Al Zn Fe Ni Sn Pb ii*Cu-"Ag" Au'^ H2 Cu Ag Au Cac cation tir K den Al khdng bi dien phan trong nude ma nude bj dien phan. 2H20+2e ^ 20H" + H2 Tgi anot: Xay ra qua trinh oxi hoa cac anion theo thir tu: - Cac anion khdng cd oxi bi dien phan - Cac anion chira oxi khdng bi dien phan ma nude bi dien phan. 2H2O ^ 4H " + O2 + 4e GV cho HS nghien ciiu SGK va yeu cau HS: - Neu cau tao cua binh dien phan. - Hien tugng xay ra khi dien phan. HS nghe giang va ghi bai HS thao luan cho ket qua: - Cdu tgo: Binh dien phan la dng chir U, 2 dien cue bang graphit, mdt dien cue am va mdt dien cue duang, dung dich chat dien phan la CUSO4. - Hiin tugng: + O catot: Kim loai Cu bam vao dien cue + d anot: Bgt khi O2 thoat ra. 53 Hogt dpng cua GV - Viet sa do qua trinh dien phan dung dich CUSO4. GV hudng dan HS cac budc viet qua trinh dien phan Buac 1. Mudi CUSO4 trong dung dich dien li thanh cac ion. Hogt dpng cua HS - Qud trinh diin phdn dung dich CUSO4 Bl. CUSO4 Cu- + SO4- Buac 2. Cae ion phan li ve eac dien cue. B2. Catot (cue am) Or". tFO B3. ar'+2e-».Cu /\not (cue duong) so/ , H2O 2Hi0-^4Fr + O,+4e Budc 3. Qua trinh oxi hoa khir d dien -circ. Buac 4. Phuang trinh dien phan. GV nhan xet va yeu cau HS viet so dd qua trinh dien phan dung dich NaCl. B4. Phuang trinh dien phan CU^ " + H2O "P"' ) Cu + 2H " + I/2O2 CUSO4+H2O 'P'' > CU+H2SO4 + I/2O2 HS thao luan va viet so dd BI. NaCl —»• Na^ + Cl' B2. Catot (cue am) Na^, H2O B3.2H20+2e-^20Fr+H2 Anot (cLic duong) cr, H2O 2Cr^-Cl2 +2e B4. Phuong trinh dien phan 2NaCl +2H2Q 'P'^ >NaOH+Cl2+H2 b) Dien phdn dung dich CUSO4 v&i anot dong (anot tan) GV tien hanh thi nghiem dien phan dung dich CUSO4 vdi cae dien cue bing Cu cho HS quan sat hien tugng xay ra d cac dien circ. Yeu cau HS 54 HS quan sat thi nghiem va nhan xet Hogt dpng ciia GV - Neu hien tugng. - Giai thich hien tugng thi nghiem. - Phuang trinh dien phan. 2+ - Nhan xet sir bien ddi ndng do Cu trong 2 trudng hgp. - So sanh pH cua dung dich sau dien phan trong 2 trirdng hgp (dien cue tra va anot tan). Hogt dpng cua HS - Hiin tugng: Day ddng lam anot nhiing trong dung dich CUSO4 tan dan va cd Cu kim loai bam len be mat catot. - Gidi thich: + 0 anot: cac nguyen tir Cu bi oxi hoa thanh ion Cu"" tan vao dung dich. Cu r -^ Cu dd + 2e + 0 catot xay ra sir khir ion Cu Cu^" + 2e -^ Cu Phuang trinh diin phdn 2+ 2+ CU(r) + C u (dd) - ^ CU(r) + C u (dd) Anot catot 2 + Kit qud Id ndng do ion Cu" khdng thay ddi - Dien phan dung dich CUSO4 vdi dien cue tra thi pH giam (vi tao ra axit). - Dien phan dung dich CUSO4 vdi dien cue anot tan thi pH khdng ddi. Hogt dpng 3 III. ITNG DUN G CUA S\J DIEN PHAN GV cho HS nghien eiai SGK trinh bay img dung ciia sir dien phan. HS nghien ciru SGK va neu cac ung dung ciia sir dien phan dudi sir hudng dan ciia GV. 1. DiSu che cac kim loai GV: cac kim loai dugc dilu che bang sir dien phan nhu the nao? - Cac kim loai tir nhdm trd ve trudc dugc dieu che bang each dien phan ndng chay mudi hoac oxit tuong img. 55 Hogt dpng cda GV Hogt dpng cua HS Vi du: 2NaCl "^^ > 2 Na + CI2 Cac kim loai tir Zn trd vl sau thudng dugc dilu chi bing each dien phan dung dich. Vi du CUSO4 + H2O ^ Cu + H2SO4 + I/2O2 2. Dieu che mot so phi kim GV gidi thieu: Phuong phap dien phan Cling dugc dung de dieu che mdt sd phi kim tir gdc anion khdng cd oxi. Yeu eau HS cho vi du Cac phi kim nhu: Clo, flo, brom, luu huynh,...deu cd the dugc dieu che bing phuang phap dien phan 2NaF 'P'" > Na + F2 3. Dieu che mot so hop chat GV yeu cau HS cho vi du ciia sir dien phan de dieu che hgp chat. Vi du dieu che NaOH 2NaCl +2H2O """ )NaOH + CI2 + H2 4. Tinh che mot so kim loai GV gidi thieu: Trong tu nhien kim loai thudng bi lan eac tap chat. Lgi dung tinh chat: Cac ion kim loai cd thii tu dien phan khac nhau, cac tap chat khdng dien phan hay khd dien phan, de tinh che cac ion kim loai de dien phan. GV yeu cau HS trinh bay cac budc de tinh che kim loai Au. 56 HS nghe giang va ghi bai HS thao luan va nhan xet: - Trudc het hoa tan Au cd lan tap chat. - Sau dd dien phan dung dich chira ion kim loai Au. Hogt dpng cua GV Hogt dpng cua HS 5. Ma dien GV eho HS quan sat mdt sd mau vat dugc ma dien nhu vanh xe dap va gidi thieu vanh dugc ma kim loai bing phuang phap dien phan vdi dien cue anot tan. HS ghi bai Hogt dpng 4 CUNG CO BAI VA BAI TAP VE NHA GV chieu cac bai tap sau len man hinh eho HS thao luan ciing cd ndi dung bai hgc: Cau 1. Dien phan vdi dien cue tra 500ml dung dich CUSO4 din khi thu dugc 1,12 lit khi (dktc) a andt thi dimg lai. Ngam mgt la sit vao dung dich sau dien phan den khi phan img hoan toan thi thiy khdi lugng la sit tang 0,8 gam. Ndng do mol cua dung dich CUSO4 ban dau la A. 3,6M B. 1,5M C. 0,4M D. 1,8M Cau 2. Khi dien phan dung dich hon hgp MgCl2. FeCl3, CuCb thi thir tu bi khu tai eatdt la A. Cu^", Fe^", Mg'", H2O B. Fe^", Cii^", Mg^", H2O C. Fe^", Cu^", Fe-", H2O D. Fe'^", Cu"". Fe"". Mg"" HS quan sat theo luan cho kit qua Cau 1. Chgn dap an D Cau 2. Chgn dap an C 57 Hogt dpng ciia GV Cau 3. Tien hanh dien phan dien cue tra 200 gam dung dich NaOH 10% din khi dung dich NaOH trong binh ed ndng do 25 % thi dirng lai. The tich khi d hai dien cue da thoat ra ia dklc) la icho Na=23: 0=16: H=l) A. 22.4 lit B. 168 lit C. 224 lit D.l 12 lit Bai tap vl nha: 1,2,3, 4, 5, 6. (SGK) Hogt dpng ciia HS Cau 3. Chgn dap an C D. HU'ONG DAN GIAI BAI TAP TRONG SGK 1. Chgn dap an B 2. Chgn dap an B 3. 0 anot xay ra phan img oxi hoa, d catot xay ra phan irng khu. Nhiing phan irng xay ra d anot la b, d, e; 0 catot la a, c. 4. a) 0 catot xay ra su khii- nhung chat khac nhau, do dd phuang trinh dien phan khac nhau. b) 0 catot, cac ion H hoac cae phan tir H2O bi khir, giai phdng khi H2. d anot: H2O bi oxi hoa, giai phdng khi O2. 5. Theo trinh tu khir cac ion Ag", Cif", Pb^" (theo tinh oxi hoa ciia cae ion giam dan). 6. Ddp so: Ndng do mol cua dung dich CUSO4 ban diu la 0,75 M, cd ndng do phan tram la 9,6%. E. TU" LIEU THAM KHAO • Dien phan la qua trinh oxi hoa - khir xay ra tren bl mat eac dien cue khi eho ddng dien mot chieu di qua chat dien li ndng chay hoac dung dich chit dien li. • Dien phan la qua trinh bien dien nang thanh hoa nang: diing ndng lugng ddng diin di thuc hiin phdn icng hod hoc (ngugc lai vdi qua trinh xay ra trong pin dien). 58 Tai Catot (K) - eirc am: Xay ra qua trinh khir (chit oxi hoa nhan e). Tai Anot (A) - cue duong: Xay ra qua trinh oxi hoa (chit khir nhu,dng e). 1. Dien phan nong chay i Thudng dimg de dien phan mgt sd mudi (chu ylu mudi halogemua), axit, hidroxit eiia kim loai kilm, kilm thd, nhdm nhim muc dich dilu chi cae kim loai dd va mdt sd phi kim nhu F2, Ch, O2,... a) Diin phan ndng chay mudi halogenua MX„-^^^M""+X K: M""+ne^ M A: 2X-^X,+2 e 9 2MX„ ^!5^^^2M + nX, T (K) (A) Vi du: Viet sa dd dien phan ndng chay mudi NaCI NaCI—^^Na " + C^ K: Na"+le^N a ^A: 2Cr->CL+2 e 2NaCl "P'" >2Na + Cl X (K) (A) b) Diin phan ndng chay oxit kim logi M20„^^2M""+nO-'^ K: M""+ne^M 4 A: 20-"->0,+2.2e n 2M,0„ dpnc -^4M + n0, T (K) (A) Vi du: Viet so dd dien phan ndng chay AI2O3. Lam ro vai trd ciia chit criolit (3NaF.AlF3 hay NasAlpA) trong qua trinh san xuit Al bing phuang phap dien phan AI2O3? 59 AE03^^^2Al""+30-'- K: Al""+3e^AI A: 20'"^0,+2.2 e 4 3 ^AKO, J::;„ )4Al + 30X (K) (A) Vai trd eiia criolit trong qua trinh dien phan: - Hoa tan AI2O3 trong criolit ndng chay se lam giam nhiet do ndng chay AI2O3 (2050 C) xudng (900 C), tiet kiem dugc nang lugng. - Tao dugc chat long ed tinh dan dien tdt hon AI2O3 ndng chay. - Hdn hgp chat dien li nay ed ti khdi nhd hon Al, ndi len tren va ngan can Al ndng chay khdng bi oxi hoa trong khdng khi. c) Diin phdn ndng chay hidoxit kim logi M(OH)„^^->M""+nOH K: A: M""+ne^ M 20H"^-0,+H, 0 + 2e 2 - 2 n 2M(0H)„ -^iH2L_^ 2M + - O, T + nH,0 (K) (A) 17 du: Viet so dd dien phan ndng chay NaOH Na(OH)-^^Na"+OH " K: A: Na" +e-^N a 20H •-0,+H, 0 + 2e 0 - 2Na0H ^P'" )2Na + -0X+H, 0 2 (K) (A) 2. Dien phan dung dich • Khi dien phan dung dich, ngoai cac ion ciia chit dien phan, cdn cd sir tham gia ciia cae ion H+, OH- (do H2O dien li) va ban than kim loai lam dien cue. 60 Nguyen tac chung: 0 catot cation nao ed tinh oxi hoa cang manh cang de bj khir va d anot anion nao cd tinh khir cang manh cang dl bi oxi hoa. 2.1. Quy tdc a Catot: hf\ //" (do H2O hoac axU dien li) a) Neu M" > Al "(cd mat eac cation tir Ap" trd vl trudc day dien hoa kim loai) -^ Tinh oxi hoa M"" « H " ^ Jon H " se bi khir. • NluH"do H20dienli: 2H,0^2H"+20H - 2H"+2e^HX 2H20 + 2e^H , t+20H - (Mot phirang phdp diiu che baza) • Neu H " do axit dien li: 2H" + 2e^H , t b) Neu M" < Al " (ed mat cation diing sau Ap" trong day dien hoa kim loai) -» Tinh oxi hoa M" " » H " (xem them phin Qua thi) -> Ion M" " se bi khir: M " " + ne -^ M (Mgt phuang phdp diiu chi kim loai) 2.2. Quy tdc &Anot: A"'' , OH (do H2O hoac baza dien li) a) Truang hgp Anot tra (C, Fe, Pt) • Nlu cd mat cac anion A""": f, Br", Cl", S^", RCOO", ... ^ tinh khir A""" OH -> A"^ se bi oxi hoa: 2Cr^Cl,t + 2e 2RC00" -> R - R + 2C0,T + 2e • Neu ed mat cac anion A"'": SO^', NO:;,F", ... -^ tinh khir A"^" OH" se bi oxi hoa: + Nlu OH" do H2O dien li: 61 H,O^H"+OH - OH--^lo X + H"+2e H.O^^O , t+2H-+2 e (Mot phuang phdp dieu chi axit) + Neu OH do baza dien li: OH"-^-0,t + H"+2e 2 - b) Tncang hgp Anot hogt dong (Zn. Cu, ...): Ban than eac kim loai nay ed tinh khir vugt trdi han han so vdi cac anion cd mat trong dung dich, vi vay chiing se tham gia vao qua trinh oxi hoa: Cu ^- Cu " + 2e Zn -> Zn" + 2e => Hien tugng duong cue (Anot) tan: NIU Anot lam bing kim loai ma ion cua nd cd mat trong dung dich thi khi dien phan: Anot se bi hoa tan din (qua trinh oxi hoa kim loai dien cue) tao ra cac ion duong M"" , cac ion duang nay di vao dung dich de bd sung cho sd ion duong da bi giam. Hien tugng dd ggi la hien tugng duong cue tan. Vi du 1: Viet so dd dien phan dung dich CUSO4 trong cac trudng hgp: a) Anot tra. b) Anot bang Zn. c) Anot bang Cu. Trong mdi trudng hgp rut ra nhan xet \'l su thay ddi khdi lugng cae dien cue K. .A. va ndng do cac ion trong dung dich. Bdi gidi: CuSO, ^Cu-"+SO ^ H.O ^ FT +oi r I K I (A ) 62 a) Anot tra K: Cu-"+2e->Cu ^- H^O->lo,+2H"+2 e Cu^" + H,0-i^^l-^Cu + lo,+2H " 2 - (K) (A) Nhdn xet: - Khdi lugng K tang do Cu bam vao va khdi lugng A khdng ddi. - Ndng do Cu^" giam, [H" ] tang (pH < 7). b) Anot bang Zn: K: Cu-"+2e->Cu A: Zn^Zn-"+2 e Cu'"+Zn-^!H^XCu + Zn-" Nhdn xel: - Khdi lugng K tang do Cu bam vao, khdi lugng A giam do Zn tan ra va mx tang < mA giam. - Ndng do [Cu "] giam va [Zn""] tang, c) Anot bang Cu: K: Cu-" + 2e -> Cu A: Cu ^Cu-' " + 2e Cu + Cu-" ^P'^' >Cu + Cu-" Nhdn xel: - mK tang = mA giam - [Cu ] khdng ddi. (Hien tugng duong cue tan, ap dung trong cdng nghe ma dien) Vi du 2: Tien hanh dien phan dung dich Na2S04 trong mdt dng chir U vdi dien cue tra (lam bang ludi dao inox hdng), eho them vao dung dich vai gigt phenolphtalein (PP). a) Md ta cac hien tugng xay ra trong qua trinh dien phan. Vilt so dd dien phan d mdi dien cue. b) Sau dd ddi ngudn dien va tiep tuc dien phan thi ed hien tugng gi xay ra? Giai thich. 63 ::rzz: DdNa2S04 Vii giot (PP)' Oien phSn dung dich Na2S04 Bdi gidi: a) Sa dd dien phan: Na.SO,-^2Na"+S0^" H,0 H" +0H" ^ K: A: 2H,0 + 2e^H , t+20H - H,0 - O , t + 2H"+2e 2 ' NajSOj •H, T + io.t H,0- dp 2 - (K) (A) Khi dien phan, d K xuat hien mdi trudng OH lam hdng phenolphtalein. Tren be mat cac dien cue K, A xuat hien bgt khi (H2 va O2). Ve ban chat, qua trinh dien phan dung dich Na2S04 la dien phan H2O (Na2S04 lam chat dan dien). b) Neu ddi ngudn dien va tiep tuc dien phan thi dung dich mau hdng d nhanh chir U se nhat dan va mat mau han. Sd dT nhu vay vi dien cue K trd thanh A va tao ra mdi trudng H trung hoa OH" va den khi du H thi phenolphtalein se khdng cd mau. Khi dd mau hdng lai xuit hien d nhanh chu U ed dien cue K vi tao ra mdi trudng OH". 3. Dien phan hon hop • Nguyin tdc: Khi dien phdn ndng chay hoac dung dich hon hgp nhieu ion thi cation nao de bi khir va anion nao de bi oxi hoa se dugc dien phan trudc. 64 • 0 Catot, cation dien phan theo thir tu: Ion kim loai ylu > H " (axit) > Ion kim loai trung binh > H " (H2O) (Ion kim loai manh thuc tl khdng bi khir trong dung djch) • 0 Anot, anion dien phan theo thu- tu: S^" > r > Br" > RCOO" > OH" (baza) > OH" (H2O) (Cac anion SO^, NO;, CO?, S0.;~, PO^, F",... thue tl khdng bi oxi hoa trong dung dich). K/ du: Viet thir tu cae phan img xay ra d dien cue khi dien phan dung dich hdn hgp: KBr, CuCl2, HCl, FeCl3. Bdi gidi: KBr -> K" + Br" CuCl2->Cu-"+2Cr . HCl ^H " + c r Feci, ^Fe' " +3Cr H,0 ^ IT + Oir Thii tu dien phan d Catot: Fe'"+le^Fe' " Cu'"+2e^Cu H-"+2e-^H, Fe'"+2e->Fe 2H,0 + 2e->H, T+20H^ Thir tu dien phan d Anot: 2Br" -> Brj + 2e 2Cr^Cl,+2 e HjO^-O,+2H"+2 e 2 - S- TKBG HOA HQC 12 NC.T2 65 4. The phan huy va qua the • Khi tiln hanh dien phan mdt chit bit ki thi ddng dien sir dung phai dat dugc mdt hieu dien thi nhit dinh mdi bat dau xay ra sir dien phan. => Hieu sd dien thi tdi thilu ciia ddng dien mdt chilu giua hai dien cue khi tiln hanh dien phan dl sir dien phan bit diu xay ra ggi la thi phdn huy. • v l mat li thuylt, thi phan huy ddi vdi mdt chit nao dd trong dung dich nude bing sire dien ddng ciia pin tao bdi eac chit thoat ra d Anot va Catot khi dien phan. Tuy nhien, trong thue tl nhilu trudng hgp thi phan huy lai ldn han suit dien ddng eiia pin dugc hinh thanh. Do chenh lech ciia the phan huy (Eph) va siic dien ddng eiia pin (Epin) dugc ggi la qua the (Eqt): En -qt t^-ph t^pin Dai lugng qua the phu thudc vao: - Ban chit cua chit thoat ra d dien cue: Thdng thudng cac khi cd qua the ldn, qua thi eiia cae san pham ran hau nhu bang khdng. - Ban chit ciia dien cue: Ching han hidro cd qua thi rit ldn tren dien cue thuy ngan, cdn tren cac dien cue khac nhu Pt, Ni, Fe qua thi be hem nhieu. - Trang thai bl mat ciia dien cue: Khi bl mat nhin bdng thi qua the cao, be mat xdp cd qua the thap. Qua th§ cua hidro va oxi tren mot s6 dien eye Dien cgc Pt (phii bot Pt) Pt(nhin bong) Fe Ni Hg Hidro 0,03-0,04V 0,20-0,40V 0,10-0,20V 0,20-0,40V 0,80-1,00V Oxi 0,3V 0,5V 0,3V 0,05V - Qua thi eiia eac cation kim loai thudng nhd va ddi vdi nhieu kim loai qua thi khdng dang kl. Vi du ddi vdi cac ion Zn ", Hg , Cu , Ag qua the coi 2+ 2+ XT-2+ nhu bing khdng. Mdt sd ion khac nhu Fe , Co , Ni , ... cd qua the kha 66 ldn. Dac biet, ion H cd qua thi d Catot rit ldn (vi qua trinh khir ion Fl" xay ra qua nhieu giai doan, phu thudc nhilu ylu td). Vi vay, mac diu hidro cd the dien cue chuin bing khdng, nhung do qua thi rit ldn nen ion H " khd bi khir hon ca mdt sd ion kim loai tir Pb^" din Mn^". Ion H " chi de bi khir hon eac cation tir Al trd ve cac ion kim loai kilm (xem quy tic dien phan d Catot). Bai 23. s y AN MON KIM LOAI A. MUC TIEU BAI HOC 1. KIdn thiPC HS biit: • Khai niem an mdn va cac dang an mdn chinh. • Cach bao ve cac dd dung may mde bing kim loai, hgp kim. HS hiiu: • Ban chat, dieu kien cua qua trinh an mdn la qua trinh oxi hoa khir trong dd kim loai bi oxi hoa thanh ion duong. • Cac bien phap bao ve kim loai khdng bi an mdn va bilt van dung mdt sd bien phap thong thudng bao ve kim loai trong ddi sdng va san xuit. 2. KT nang Van dung kien thire hieu biet ve pin dien hoa hgc dugc de giai thich hien tugng an mdn dien hoa hgc. 3. Tinh cam, thai do Cd y thiic bao ve kim loai, chdng am mdn kim loai do hieu rd nguyen nhan va tac hai ciia hien tugng an mdn. B. CHUA N B! CUA GV VA HS • GV: Cae bang phu, hinh ve ve hien tugng an mdn dien hoa. • HS: On tap bai tinh chat cua kim loai va day dien hoa kim loai. Xem trudc bai su an mdn kim loai. 67 C. TI^N TRiNH DAY - HOC Hogt dpng cda GV Hogt dpng cua HS Hogt dpng 1 I. KHAI NIEM GV cho HS nghien cim SGK va yeu cau HS neu: - Khai niem sir an mdn. - Ban chat cua sir an mdn kim loai. Hoac GV cd the day theo hudng sau: GV gidi thieu: Trong cugc sdng, chimg ta quan sat thudng thay: Dd diing bang sat, thep... sau mdt thdi gian sir dung bi gi set, khi bi gi set ed cdn la thep nira khdng? Tir dd dan dat HS di den khai niem: + Ban chat ciia sir an mdn kim loai. + Cac dang an mdn kim loai. H HS nghien cim SGK va nhan xet - Khdi niem: Sir an mdn kim loai la sir pha huy kim loai hoac hgp kim do tac dung cua cac chat trong mdi trudng xung quanh. - Bdn chdt cua sir an mdn kim loai: Kim loai bi oxi hoa thanh ion duang. M -> M " + ne ^ogt dpng 2 II. HAI DANG l.An GV eho HS nghien ciiu SGK va yeu cau HS neu: - An mdn hoa hgc la gi? 68 AN MON KIM LOAI mon hoa hoc HS nghien cim SGK va nhan xet An mdn hod hoc la qua trinh oxi hoa - khir. trong dd eac electron ciia kim loai dugc chuyen true tiep den cac chat trong moi trudng. Hogt dpng cua GV - Cho vi du vl: Sir an mdn hoa hgc, thudng xay ra d dau? Hogt dpng cua HS - Thudng xay ra d: Ld dot, ndi hai, chi tilt ciia ddng ca ddt trong... Fe + H2O - ^ Fe304 + H2 - Dimg hop nhdm dung xa phdng, giim. 3+ 2AI + 6H' ->2Ar 2. An mon dien hoa hoc a) Khdi niim vi dn mdn dien hod hgc GV lam thi nghiem: Nhung thanh HS quan sat thi nghiem kem va thanh ddng khdng tilp xuc vdi nhau vao cdc dimg dung dich H2SO4 loang. Ndi thanh kem vdi thanh ddng bang day dan cho di qua mdt vdn ke. Cho HS quan sat yeu ciu HS - Neu hien tugng. 3H2 - Giai thich. Kit qua thi nghiem. - Hien lugng: Kim vdn ke quay, chiing td cd ddng dien chay qua. Thanh Zn bi mdn din, d thanh Cu cd bgt khi thoat ra. - Gidi thich: . + 0 dien cue am (anot), kem bi an mdn theo phan irng: Zn -^ Zn " + 2e 2+ Ion Zn di vao dung dich, cdn electron theo day dan sang dien cue ddng. + 0 dien cue duong (catot), ion H " cua dung dich H2SO4 nhan electron biln thanh nguyen tir H rdi thanh phan tir H2 thoat ra: 2 H " + 2e -> H2t Ket qua 69 Hogt dpng cda GV Hogt dpng cda HS Giro am: Zn Zn Zn^"+2e Cue duong: Cu 2Fr + 2e ^ Hjt GV nhan xet trong thi nghiem tren thi Zn bi an mdn theo kieu an mdn dien hoa hgc va tir dd yeu cau HS neu khai niem an mdn dien hoa hoc. GV bd sung: Can phan biet an mdn hoa hoc va an mdn dien hoa hgc: An mdn dien hoa hgc cd tao ra ddng dien gian tiep qua day dan hoac dung dich dien li. Ket qua thanh Zn bi an mdn HS thao luan cho nhan xet: An mdn dien hod hoc la qua trinh oxi hoa - khir, trong dd kim loai bi an mdn do tac dung ciia dung dich chat dien li va tao nen ddng electron dhuyen ddi tir cue am den cue duong. b) Diiu kiin xay ra dn mon diin hod hgc GV chuyen tiep: Thi nghiem thanh Cu va thanh Zn trong H2SO4 va sir md ta qua trinh an mdn gang thep. Yeu cau HS thao luan dudi su dieu khien eiia GV de neu dieu kien ciia su an mdn dien hoa hoc. GV luu y cho HS: Thieu mdt trong ba dieu kien tren se khdng xay ra sir an mdn dien hoa. GV gidi thieu eau tao cua pin dien hoa tuan theo dieu kien an mdn dien hoa hoe. 70 HS thao luan cho ket qua - Cac dien cue phai khac chat nhau, cd the la cap 2 kim loai khac nhau hoac cap kim loai vdi phi kim. - Cac dien cue phai tiep xuc true tiep hoac gian tiep vdi nhau qua day dan. - Cac dien cue cimg tiep xiic vdi dung dich chat dien li. Hogt dpng cua GV Hogt dpng cua HS c) An mdn diin hod hgc hgp kim sdt (gang, thep) trong khdng khi dm GV gidi thieu: - Trong khdng khi im, tren bl mat ciia sat ludn ed mdt ldp nude rit mdng da hoa tan O2 va khi CO2 trong khi quyln, tao thanh mdt dung dich chat dien li. - Sat va cac tap chat (chu ylu la cacbon) eiing tiep xuc vdi dung dich do tao nen vd sd pin rit nhd ma sat la anot (cue am) va cacbon la catot (cue duong). GV hudng dan HS viet eac qua HS viet eac qua trinh dudi sir dieu khien ciia trinh cho nhan electron d cac dien GV cue va neu kit qua eiia sir an mdn. _ j^ j ^^Q^, sit bi oxi hoa thanh ion Fe'" 2+ Fe -> Fe 2e Cae electron dugc giai phdng chuyen dich den catot. - Tai vimg catot, O2 hoa tan trong nude bi khir thanh ion hidroxit: O2 + 2H2O + 4e ^ 40H" - Ket qua eiia qua trinh Cue am: tinh the Fe Fe -^ ¥i* +2e Cue duong: tinh the C 02+2H2CH-4e^40Fr GV bd sung: Khi tan vao dung dich dien li thi ion Fe " cd them cac qua trinh tao gi sat: Fe'" + 20H" -^ Fe(0H)2 Vat bang gang, thep (hgp kim ciia Fe, C,...) bi an mdn theo kieu dien hoa. 71 Hogt dpng cua GV Hogt dpng cua HS 4Fe(OH)2 + 02(kk) + 2H2O -> 4Fe(OH)3 Fe(OH),, Ph^-'"h"y > Fe,0.,.xH.,0 Gi sat Hogt dpng 3 III. CHONG AN MON KIM LOAI GV neu tac hai eiia su an mdn dien hoa (hay eho HS dgc SGK). GV neu nguyen tac ciia phuang phap chdng an mdn dien hoa la ngan can mot trong ba dieu kien an mdn dien hoa va yeu cau HS de xuat cac phuong phap chdng an mdn. \. Phu'ong GV chia nhdm HS: Yeu cau HS nhdm 1: Neu cac phuang phap bao ve be mat, cho vi du minh hoa. HS thao luan cho eac phuang phap: - Ngan cho vat lieu tiep xuc ciing vdi mot dung dich dien li. - Khdng cho 2 vat lieu tiep xiic vdi nhau. - Diing vat lieu khac de thay the vat lieu can bao ve.... ihap bao ve be mat HS nhdm 1 thao luan cho ket qua Diing nhirng chat ben viing ddi vdi mdi trudng de phii ngoai mat nhiing do vat bang kim loai nhu bdi dau md, son, ma, trang men,... Vi du: Sat tay la sat dugc trang thiec, tdn la sat dugc trang kem. Cac dd vat bang sat thudng dirge ma niken hay crom. 2. Phuong phap dien hoa Yeu cau HS n''dm 2: Neu eac phuang phap dien hoa de bao ve kim loai, cho vi du minh hoa. 72 HS nhdm 2 thao luan cho ket qua Ndi kim loai can bao ve vdi mdt kim loai hoat ddng hon de tao thanh pin dien hoa va Hogt dpng cda GV Hogt dpng cda HS kim loai hoat ddng hon bi an mdn. kim loai kia dugc bao ve. Vi du: De bao ve vd tau bien lam bang thep va vd tau (phan chim dudi nude), dng thep dan nude, dan dau. dan khi ddt d dudi dit, ngudi ta lap vao mat ngoai ciia thep nhirng khdi kem. Ket qua la kem bj nude biln hay dung dich chit dien li d trong dit an mdn GV bd sung: Ngoai 2 phuang phap tren thi ngudi ta cdn dimg: - Chat kim ham (chit tie ehi) lam cham qua trinh an mdn. - Sir dung cae vat lieu khdng an mdn nhu inox de thay the. thay cho thep. Hogt dpng 4 CUNG CO BAI VA BAI TAP VE NH A GV chieu eac bai tap sau len man hinh cho HS thao luan ciing cd ndi dung bai hgc: Cau 1. Tien hanh bdn thi nghiem sau - Thi nghiem 1: Nhiing thanh Fe vao dung dich FeC13 - Thi nghiem 2: Nhiing thanh Fe vao dung dich CuS04 - Thi nghiem 3: Nhiing thanh Cu vao dung dich FeC13 - Thi nghiem 4: Cho thanh Fe tiep xiic vdi thanh Cu roi nhiing vao dung djch HCl. HS quan sat theo luan cho kit qua Cau 1. Chgn dap an B 73 Hogt dpng cda GV Sd trudng hgp xuat hien an mdn dien hoa la: A.l B.2 C.4 D. 3 Cau 2. Khi vat bang gang, thep bi an mdn dien hoa trong khdng khi am, nhan dinh nao sau day dung? A. Tinh the sat la cue duang, xay ra qua trinh khir. B. Tinh the sat la cue am, xay ra qua trinh oxi hoa. C. Tinh the cacbon la cue duong, xay ra qua trinh oxi hoa. D. Tinh the cacbon la cue am, xay ra qua trinh oxi hoa. Bai tap ve nha: 1, 2, 3, 4, 5 (SGK) Hogt dpng cua HS Cau 2. Chgn dap an B D. HU'ONG DAN GIAI BAI TAP TRONG SGK 1. Ban chat gidng nhau (ciing la phan img oxi hoa - khir) Khac nhau: Trong an mdn dien hoa hgc, nang lugng do phan iing oxi hoa - khir sinh ra dugc chuyen hoa thanh dien nang. Trong an mdn hoa hgc, nang lugng dd dugc chuyin hoa thanh nhiet nang (khdng phat sinh ddng dien). 2. Chgn dap anB. Phan img oxi hoa-khir. 3. Chon dap an B. 4. Chd ndi eiia 2 kim loai Al - Cu trong tu nhien ed du dilu kien hinh thanh hien tugng an mdn dien hoa hgc. Al la cue am bi an mdn nhanh. Day bi dut. Ket luan: Khdng nen ndi bing nhirng kim loai khac nhau, nen noi bing doan day Cu. 5. a) Zn va Sn la nhung kim loai hoat ddng, nhung trong tu nhien chiing diu dugc bao phii bang ldp mang mdng oxit dac kbit ma cac chit khi va nude khdng tham qua duac. Do vay cd thi diing dl bao ve sit. 74 b) Hien tugng va ca chi an mdn: Hien tugng: 0 nhimg chd xay sat cua ca 2 vat diu xay ra hien an mdn dien hoa kim loai. - 0 vet xay sat tren vat trang thiic (Sn) xuit hien chit rin mau nau dd (gi sat). Tren vat trang kem (Zn) xuit hien chit rin dudi dang bdt mau tring (hgp chat ciia kem). Bai 24. Dieu CHt KIM LOAI A. MUCTIEUBAI HOC 1. Ki§n thu'c HS biit: • Nguyen tac chung dieu chi kim loai. • Cac phuong phap dieu chi kim loai. • Phan biet dien phan dung dich va dien phan ndng chay. HS hiiu: • Phuang phap dieu che kim loai cd miic do hoat ddng khac nhau. • Sir khac nhau giira cac phuong phap dieu che kim loai. 2. KT nang • Ren luyen tu duy: Tir tinh khir khac nhau ciia kim loai biet each chgn phuang phap thich hgp de dieu che kim loai. • Tinh toan vdi cdng thiic Faraday. 3. Tinh cam, thai do Thdng qua each dilu chi kim loai la cho HS himg thu vdi mdn hoa hgc va bilt quy trgng kim loai. B. CHUAN B! CUA GV VA HS • GV: May tinh, may chilu: Tranh anh sa dd binh (be) dien phan, phim md phdng qua trinh dien phan. • HS: On tap bai tinh chit kim loai va day dien hoa, xem trudc bai dieu chi kim loai. 75 C. TltN TRiNH DAY - HOC Hogt dpng cua GV Hogt dpng cua HS Hogt dpng 1 I. NGUYEN TA C DIE U CHE KIM LOAI GV yeu eau 1 HS neu tinh chit chung ciia kim loai. Tir dd neu nguyen tac dilu ehi kim loai HS tinh chat chung cua kim loai la tinh khii-: M -n e j-M"" => Nguyen tdc diiu chi kim logi la khir ion kim loai thanh nguyen tir. M"" + ne -^ M° Hogt dpng 2 II. PHU'ONG PHAP DIEU CHE KIM LOAI GV gidi thieu: Tuy va each thtic, dilu kien khir ion kim loai thanh kim loai ma ngudi ta chia lam 3 phuang phap sau: \. Phu-oTjg phap thuy luyen GV neu nguyen tac ciia phuang phap: - Hoa tan kim loai hoac hgp chit ciia kim loai va tach ra khdi phin khdng lan cd trong quang bing nhiing dung mdi thich hgp nhu dung dich H2SO4, NaOH. NaCN,... - Khir nhung ion kim loai trong dung dich bang kim loai cd tinh khir manh nhu: Fe, Zn,... GV yeu cau HS viet cae phuang trinh hoa hgc dang phan tir va dang ion. GV luu y HS phuang phap thuy luyen thucmg dimg dl dilu chi cac kim loai CO tinh khxxyeu nhu: Ag, Au, Pt... 76 HS ghi bai va vilt phuong trinh hoa hoc minh hoa: - Fe + CUSO4 -^ FeS04 + Cu Fe + Cu^" ^ Fe^"+ Cu - Zn + Ag" -^ Zn"" + 2Ag Hogt dpng cda GV Hogt dpng ciia HS 2. Phu-oTig phap nhiet luyen GV neu nguyen tic cua phuang phap: Diing cae chit khir nhu C, CO, H2, HS ghi bai va viet cac phuong trinh hoa hoc: Al... khu cac ion kim loai (thudng la oxit kim loai) thanh kim loai d nhiet do cao. GV yeu ciu HS vilt cac phuang trinh hoa hgc minh hoa cho cac chit khir tren. GV luu y HS phuang phap nhiet luyen thudng diing de dilu chi eac kim loai cd tinli khir trung binh tir Zn trd vl sau trong day dien hoa (Zn, Fe, Sn, Pb,...). CuO + H2 Fe304 + 4C0 Fe203 + 2A1 -^ Cu + H2O ^3F e + 4CO2 '-^ 2Fe + AI2O3 3. Phu-ong phap dien phan GV gidi thieu: - Nguyen tdc diin phdn: Dimg ddng dien mdt chieu tren catot dl khir cac ion kim loai trong hgp chit d trang thai long (dung dich hay ndng chay). GV yeu cau HS viet sa do cua qua trinh dien phan dung dich CuC^. HS viet sa dd dien phan dung dich CuCl2 CuCh—•Cu-•2+ + 2cr Catot (-) Cu^'",H20 Cu^"+2e-^Cu Anot (+) cf, H2O 2Cr-2e-K:i2 Phuang trinh hda hgc .2+ Cu^ +2Cf±^ Cu + CI2 CuCl2 '-^^^^ Cu + CI2 77 Hogt dpng cda GV GV nhac lai giup HS luu y: - Thir tu khir cac ion kim loai: Ion ed tinh oxi hoa ldn thi khir trudc F; Jw; Ag">Cu^">Fe^"... - Thir tu oxi hoa tai anot: ion cd tinh khir manh thi oxi hoa trudc 1" > Br" > c r > H2O > S04^" >N03"... (cae anion cd oxi khdng bi dien phan trong dung dich) - Cac nira phan iing khir H2O O catot: H2O + 2e -^ 20H~ + H21 Oanot: H2O - 4e -^ 4H " + 02 t a) Diin phan hgp chat ndng chay GV gidi thieu: Nhung kim loai cd do hoat ddng manh nhu K, Na, Ca, Mg, Al dugc dieu che bang phuong phap Hogt dpng cda HS HS ghi bai HS thao luan cho ket qua AI2O3 -^ 2Al^" + 30^" dien phan hgp chat ndng chay. Yeu cau HS viet qua trinh dien phan Catot - Al^" + 3e - Anot + A r 20^" - 4e ^ O2 ndng chay AI2O3. b) Diin phdn dung dich GV gidi thieu: De dilu ehi eac kim loai cd do hoat ddng trung binh hoac yeu bang each dien phan dung dich mudi ciia chiing. Phuong trinh hoa hgc 2AI2O3 'P"^ ) 4AI + 3O2 HS thao luan vilt qua trinh dien phan Dien phan dung dich AgN03 AgN03 ^ Ag" + NO3" Thi du: Dien phan dung dich AgN03 de dieu che Ag. 78 Catot - Ag", H2O A + , A 0 Ag +e ^ Ag Anot + NO3-, H2O 2H20^e->4H"+02 Hogt dgng cda GV Yeu eau HS vilt qua trinh dien phan dung dich AgN03, dung dich FeCb Hogt dpng cua HS Phuong trinh hoa hoc 4AgN03+ 2H2O -^ 4Ag + 4HNO3+ O2 Dien phan dung dich FeCl2 FeCl2 -^ Fe^" + 2Cr Catot - Fe^", H2O Fe +2e —>Fe Phuang trinh hoa hgc Anot + Cl", H2O 2Cr-2e^Cl 2 Hogt FeCl2 'P'' > Fe + CI2 dpng 3 III. DINH LUAT FARADAY GV gidi thieu: Dua vao cdng thirc bieu dien dinh luat Faraday ta cd the xac dinh dugc khdi lugng cac chat thu dugc d dien cue: Alt m = — trong do: nF m: Khdi lugng chat thu dugc d dien cue (gam). A: Khdi lugng mol nguyen tir ciia chat thu dugc d dien cue. n: Sd electron ma nguyen tir hoac ion da cho hoac nhan. 1: Cudng do ddng dien (ampe). t: Thdi gian dien phan (giay). F: la hing sd Faraday: F = 96500. GV chilu len man hinh bai tap sau eho HS van dung cdng thuc dien phan HS ghi bai HS thao luan cho ket qua """