- #1

mburt

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## Homework Statement

What voltage must be applied to decrease the mass of Ag(s) in the electrolytic cell

reaction below?

2 Ag

^{+}(aq) + Cd(s) → 2 Ag(s) + Cd

^{2+}(aq)

## Homework Equations

Standard reduction potential of Ag

^{+}: Eo = +0.80 V

Standard reduction potential of Cd

^{2+}: Eo = -0.40 V

## The Attempt at a Solution

Since the question says that Ag(s) will lose mass, I assume it must be oxidized so I wrote the equation:

Ag(s) → Ag

^{+}+ e

^{-}where Eo = -0.80 V (Change sign,cause oxidation)

and therefore the reduction reaction is:

Cd

^{2+}+ 2e- → Cd(s) where Eo = -0.40 V (keep sign)

So the net voltage is : -1.20 V... so the req'd voltage to make this non-spontaneous reaction occur is +1.20 V.

But the answer in the answer key says the req'd voltage is +1.30 V. Note that this is a multiple choice question and the answer of +1.20 V was an option as well.

Thanks!