Why does the flow of current gets reversed when external potential (greater than1.1V)is applied in an electrochemical cell?

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Solution

Dear student,
In the beginning, the external opposing potential is less than 1.1 V. In this case, the normal reaction occurs in Zn- CuSO₄ cell and net current flows from copper electrode to zinc electrode. The opposing potential is now increased slowly and gradually.It is observed that the normal reaction continuous to occur till the opposing potential reaches a value of 1.1V. At this stage the cell reaction stops and no current flows. Further increase in the opposing potential (beyond 1.1V) again causes the chemical reaction to occur. But now the reaction occurs in the reverse direction forcing Zn²⁺ion to get reduced and Cu atoms to get oxidised
Cu + Zn²⁺.................Cu²⁺ + Zn
The flow of current in this case occurs from Zn- electrode to Cu- electrode. This process is non spontaneous and involves the use of electrical energy to carry out the redox reaction. In this situation the Zn- CuSO₄ cell starts acting as an electrolytic cell. This phenomenon is also called recharging of the electrochemical cell.

Regards,

Aparna

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