Cu2+ +H2S=CuS +2H+
由于在酸性条件下S2-不大,Cu2+浓度有降低,因此ECu2+/Cu 显然降低
因此ECuS/Cu 仍作正极极,
0.67V=E(CuS/Cu)-E0(Zn2+/Zn)
E(CuS/Cu)=0.67V-0.763V =-0.093V
1) (-)Zn |Zn2+(1mol/L)||H2S(0.1mol/L ),H+(c)|CuS,Cu(+)
正极:CuS +2e- +2H+ =Cu+H2S
负极:Zn2+ +2e-=Zn
2)正极:CuS +2e- +2H+ =Cu+H2S
正极的本质: Cu2+ +2e-=Cu
因此-0.093V=E0(Cu2+/Cu)+0.0591V/2 *lg[Cu2+]
[Cu2+]=2.81*10^-15
3)Cu2 + H2S =CuS +2H+
0.1 0.2
由于Cu2+基本完全反应因此c(H+)=0.2mol/L
H2S<=>H+ +HS-
HS-<=>H+ +S2-
H2S<=>2H+ + S2- K=Ka1*Ka2=5.7*10^-8 *1.2*10^-15=6.8*10^-23
K=[H+]^2 *[S2-]/[H2S]=6.8*10^-23
(0.2)^2 *[S2-]/ 0.1=6.8*10^-23
[S2-]=1.71*10^-22
因此CuS的Ksp=[Cu2+]*[S2-]=2.81*10^-15*1.71*10^-22=4.8*10^-37