Question

An electrochemical cell is based on the following two half-reactions: oxidation: Sn(s)→Sn2+(aq, 1.50 M )+2e− reduction: ClO2(g, 0.180 atm )+e−→ClO−2(aq, 1.65 M ) Compute the cell potential at 25 ∘C.

Answer 1

• We have the following two half-reactions:

1. Oxidation: Sn(s)→Sn2+(aq, 1.50 M )+2e−
2. Reduction: ClO2(g, 0.180 atm )+e−→ClO−2(aq, 1.65 M )

• To calculate the cell potential, we use the formula: Ecell = E°cell - (RT/nF)ln(Q)

• Where:

E°cell = Standard state cell potential

R = 0.0821 Lkmol^-1K^-1 (gas constant)

T = 298 K

n = Number of electrons transferred in balanced redox reaction = 2 (from the half-reactions)

F = 96485 C/mol (Faraday's constant)

Q = Reaction quotient = [Sn^2+] [ClO2^-] / [Sn] [ClO2]

1. Standard state cell potential (E°cell): Since we have Sn/Sn^2+ and ClO2/ClO2^- half-cells, E°cell = E°Sn/Sn^2+ - E°ClO2/ClO2^-

= -0.76 V - 0.94 V = -1.7 V

2. Reaction quotient (Q):

[Sn^2+] = 1.50 M

[ClO2^-] = 1.65 M

[Sn] = 1 M (assumed, since Sn is solid)

[ClO2] = 0.180 atm = 0.180 M

So Q = (1.50 M) (1.65 M) / (1 M) (0.180 M) = 9:1

3. Substitute into cell potential formula:

Ecell = -1.7 V - (0.0821 Lkmol^-1K^-1 * 298 K) * ln(9)

Ecell = -1.7 V - 0.0613 * ln(9)

Ecell = -1.76 V

So the cell potential at 25°C is -1.76 V

Let me know if you have any other questions!