Question

Based on your measured potential for this cell and the literature value for the standard reduction potential for the ag/agcl reference electrode, what would you expect the overall potential to be for the spontaneous reaction between your cu2+/cu electrode and a standard hydrogen eletrode? type your calculation for the expected standard reduction potential vs the she as well as the % error between this value and the literature value.

Answer 1

I have attached an image that shows the measured cell potentials, and this question specifically refers to cell #4 with the following reaction:

Cu²⁺(aq) + 2Ag(s) → Cu(s) + 2Ag⁺(aq)    Ecell = 0.137 V

We can separate this reaction into its two half reactions to identify the anode and cathode:

Cathode: Cu²⁺ + 2e⁻ → Cu    E° = 0.34 V
Anode: Ag → Ag⁺ + 1e⁻         E° = 0.22 V

The formula for cell potential is:

Ecell = Ecathode - Eanode

We are asked to solve for the cell potential of the Cu²⁺/Cu electrode using the standard Ag/AgCl electrode potential and the measured potential:

0.137 V = Ecathode - 0.22 V
Ecathode = 0.137 + 0.22
Ecathode = 0.357 V

Now we can compare this value for the Cu²⁺/Cu electrode with the standard hydrogen electrode:

Ecell = 0.357 V - 0 V
Ecell = 0.357 V

We found a value of 0.357 V, however, the literature value is 0.34 V and now we can solve for the % error in our experimental value:

% error = ([experimental - theoretical]/[theoretical]) x 100%

% error = ((0.357 - 0.34)/0.34) x 100%

% error = 5 %

The experimental electrode potential for the Cu²⁺/Cu electrode was 0.357 V which has a 5% error compared to the literature value.