A cell is represented by Zn∣∣Zn2+(aq)∣∣∣∣Cu2+(aq)∣∣Cu. Given, Cu2++2e−⟶Cu,E∘=+0.35V and Zn2++2e−⟶Zn,E∘=−0.763V. Write the cell reactions, emf of the cell and state whether the cell reaction will be spontaneous or not?
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Solution
The given cell is
Zn∣∣Zn2+(aq)∣∣∣∣Cu2+(aq)∣∣Cu
Half-cell reaction at anode
Zn⟶Zn2++2e− [oxidation]
Half-cell reaction at cathode [reduction]
Cu2++2e−⟶Cu
Overall reaction, Zn+Cu2+⇌Zn2++Cu
E∘cell=E∘R−E∘L
=E∘Cu2+/u−EZn2+/Zn
=0.35−(−0.763)
∴E∘cell=1.113V
Positive value of E∘cell shows, cell reaction is spontaneous.