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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.
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.