Question

How do you calculate the Theoretical standards of the cell potentials for all 6 (1.0 M) cells listed below?

Cu+2 and Zn

Cu+2 and Pb

Cu+2 and Ni

Zn and Pb

Zn and Ni

Pb and Ni

Answer 1

Remember that each species will have a specific reduction potential. Remember that this is, as the name implies, a potential to reduce. We use it to compare it (numerical) with other species.

Note that the basis if 2H+ + 2e- -> H2(g) reduction. Therefore E° = 0 V

All other samples are based on this reference.

Find the Reduction Potential of each reaction (Tables)

X+2 + 2e- = X(s) Ered

Y+ + e- = Y(S) E red

The most positive has more potential to reduce, it will be reduced

The most negative will be oxidized, since it will donate it selectrons

a)

Cu2+ + 2 e− ⇌ Cu(s) +0.337;

Zn2+ + 2 e− ⇌ Zn(s) −0.7618;

Pb2+ + 2 e− ⇌ Pb(s) −0.126;

Ni2+ + 2 e− ⇌ Ni(s) −0.25

Cu+2 and Zn

a) E°red = 0.337 - -0.7618 = 1.099 v

Cu+2 and Pb

b) E°red = 0.337 - -0.126 = 0.463 V

Cu+2 and Ni

c) E°red = 0.337 - -0.25 = 0.587 V

Q2

Zn and Pb

d) E°red = -0.126- -0.7618 = 0.6358 V

Zn and Ni

e) E°cell = -0.25 - -0.7618 = 0.5118 V

Pb and Ni

f) E°cell = -0.126 - - 0.25 = 0.124 V