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Cho pin in: Ag| AgNO3 0,001M,Na2S2O3 0,1M || HCl 0,05M | AgCl,Ag.a/Vit PTP xy ra khi pin hot ng:

Ag+ + 2S2O32- [Ag(S2O3)2]3-. = 1013,46.10.3 0,1

[] 0 0,098 10-3.

Do Epin > 0, nn ta c pin vi 2 cc nh sau:-- Ag| AgNO3 0,001M, Na2S2O3 0,1M || HCl 0,05M | AgCl , Ag. +Khi pin hot ng:Anot(-): Ag + 2S2O32- [Ag(S2O3)2]3- + e (0,25 im)Catot(+): AgCl + e Ag + Cl- (0,25 im)

PTP : AgCl + 2S2O32- [Ag(S2O3)2]3- + Cl-. (0,25 im)

b/ Tnh Eo[Ag(S2O3)2]3- /AgAg+ + e Ag K1=10(0,8 / 0,059)[Ag(S2O3)2]3- Ag+ + 2S2O32- -1 = 10 -13,46.

[Ag(S2O3)2]

3-

+ e Ag

+ 2S2O32-

K2= 10

(Eo/0,059)

=K1.

-1

. E0=Eo[Ag(S2O3)2]3- /Ag = 5,86.10-3V. (0,5 im)c/ Tnh TAgCl.Eanot=E[Ag(S2O3)2]3- /Ag = Eo[Ag(S2O3)2]3- /Ag + 0,059.lg ([Ag(S2O3)2]3- / [S2O32-]2.

= 5,86.10-3 + 0,059.lg (10-3 / 0,0982) = -0,052 V. (0,25 im)Epin = Ecatot Eanot = 0,345. Ecatot= 0,293 V = EAg+/Ag = EoAg+/Ag + 0,059.lg[Ag+] (0,25 im) [Ag+] TAgCl = [Ag+][Cl-] = 10-8,59.0,05 = 10-9,89=1,29.10-10. (0,25 im)d/ Thm t dung dch KCN vo dd na tri pin. Epin?[Ag(S2O3)2]3- Ag+ + 2S2O32- -1 = 10 -13,46.Ag+ + 2CN- [Ag(CN)2]- =1021.

[Ag(S2O3)2]

3-

+ 2CN

-

[Ag(CN)2]

-

+ 2S2O32-

K = 10

-13,46

.10

21

=10

7,54

(0,25 im)Ta thy, phc [Ag(CN)2]- bn hn phc [Ag(S2O3)2]3- .Vy:+ nng ca Ag+(hay nng ca [Ag(S2O3)2]3- gim) Eanot gim (0,25 im)+ Eanot=const. Epin = Ecatot Eanot : tng. (0,25 im)

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Bi :(2im) 25oC, cho pin Pt,H2 (k,po) | KOH(1,00M) | Ni(OH)2 (r),Ni (r) c sc in ng l 0,108V.a/ Vit phng trnh phn ng xy ra cc in cc v phng trnh phn ng xy ra khipin hot ng.

b/ Hiro v oxi trong cng 1 dung dch to thnh 1 pin, khi p sut ring ca mi kh ul po th sc in ng ca pin l 1,229 V.hidro v oxi trong dung dch KOH to thnh 1pin vi phng trnh phn ng l: H2 (k) + O2(k) H2O (l).Vit phng trnh phn ng ca pin v oxi trong dung dch KOH, Tnh th in ccchun ca oxi 25oC.c/ 25OC:Ni(OH)2 (r) Ni (r) + O2 (k) + H2O (l). Tnh hng s cn bng Ko ca phn ng trnv phn on xem phn ng trn c th xy ra trong khng khhis kh hay khng? (khngkh kh c pO2 = 0,21po).Bi gii:a/ cc dng: Ni(OH)2 (r) + 2e Ni (r) + 2OH- (1) (0,125 )

Cc m: H2 (k) + 2OH

-

2H2O (l) + 2e (2) (0,125)Ni(OH)2 (r) + H2 (k) Ni (r) + 2H2O(l) (3) (0,125 )b/ Trong dung dch KOH, phn ng ca pin to bi cc hiddro v cc oxi l:

H2 (k) + O2 (k) H2O (l) (4)Cc dng: O2 (k) + H2O (l) + 2e 2OH- (5) (0,125)Cc m: H2 (k) + 2OH- 2H2O (l) + 2e (6) (0,125)E_= EoOH- / H2 =EH+/H2= EoH+/H2 RT/2F.ln (PH2 /Po ) / (CH+/Co)2. Th CH+ = 1,00.10-14

(mol/L).E_ = -0,828V.E+=EoO2 /OH- - RT/2F.ln (COH- /PCo)2 /(PO2 /Po)1/2 = EoO2 / 2OH-E = 1,229V = E+ - E_ =EoO2/ 2OH- -(-0,828V)

EoO2 / OH- = 1,229 - 0,828 = 0,401V (0,25)c/ (3) (4)cho:Ni(OH)2 (r) Ni(r) + O2 (k) + H2O (l) (7)Go(T) = Go(3) - Go(4) .Trong : Go(3) = -Z3.FEo3 ; Go(4) = -Z4.FEo4.Go(3) = -2.FEo3 -( -2.FEo4) Eo3=E3 + RT/2F.ln 1/(PH2 /Po) = E3 = 0,108V.

Eo4=E4+ RT/2F.ln 1/(PH2 /Po.(PO2 /Po)1/2) = E4 = 1,229V.Go(7) = -2FEo3 + 2FEo4 = 2.96500.(1,229 0,108) = 2,16.105 (J.mol-1).P (7) c: Ko= e(-G2(bnh phng) /RT) =1,37.10-38 .(0,5)

Phn ng ng nhit nn:G= Go + RT.ln QP = -RT.lnKo + RT.lnQP = RT.ln (QP/Ko)Trong khng kh kh: QP=(PO2/Po)1/2 = 0,21 = 0,46 QP > Ko. (0,25)Phn ng khng th xy ra. (0,25).

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