Question

A galvanic cell has electrical potential of $1.1$ V. If an opposing potential of $1.1$ V is applied to this cell, what will happen to the cell reaction and current flowing through the cell?

• A. The reaction stops and no current flows through the cell
• B. The reaction continuous but current flows in opposite direction
• C. The concentration of reactants becomes unity and current flows from cathode to anode
• D. The cell does not function as a galvanic cell and zinc is deposited on zinc plate

Answer 1

Answer: (A)

The reaction stops and no current flows through the cell

We can study the effect of opposing potential applied to a galvanic cell as follows.

1) When $E_{external}<1.1V$
In a galvanic cell, if an external opposite potential is applied and increased slowly, we find that the reaction continues to take place till the opposing voltage reaches the value 1.1 V.
2) When $E_{external}=1.1V$
When the external voltage is 1.1V the reaction stops altogether and no current flows through the cell.
3) When $E_{external}>1.1V$
Any further increase in the external potential again starts the reaction but in the opposite direction. It now functions as an electrolytic cell, a device for using electrical energy to carry non-spontaneous chemical reactions.

Hence option (A) is correct.