We are asked to calculate the change of the potential (voltage) of the cell caused by the discharge.
We are given the following values based on the previous items:
[Zn2+]final = 0.602 M
[Cu2+]final = 0.003 M
Ecell initial = 1.07 V
E°cell = 1.10 V
n = 2 e-
We will use the Nernst Equation to calculate the cell potential. The Nernst Equation relates the concentrations of compounds and cell potential.
Ecell = cell potential under non-standard conditions
E°cell = standard cell potential
n = number of e- transferred
Q= reaction quotient = [products]/[reactants]
We go through the following steps to solve the problem:
Step 1. Calculate the final cell potential (Ecell)
Step 2. Calculate the change in voltage
An electrochemical cell (battery) consists of a Cu plate immersed in 100 mL of 0.055 M Cu2+ solution and a Zn plate immersed in 100 mL of 0.550 M Zn2+ solution. The two compartments are connected by a salt bridge and the cell is maintained at 25 °C. The cell is discharged by passing a 10.00 mA current for 105 seconds.
The standard reduction potentials are given below:
Cu2+ (aq) + 2 e- → Cu (s) ε°red = + 0.34 V
Zn2+ (aq) + 2 e- → Zn (s) ε°red = - 0.76 V
What is the change of the potential (voltage) of the cell caused by the discharge? Please circle your answer.