Q57 / 180 · AIIMS 2006 · Chemistry
Assertion : For the Daniel cell, $\mathrm{Zn}\left|\mathrm{Zn}^{2+} \| \mathrm{Cu}^{2+}\right| \mathrm{Cu}$ with $E_{\text {cell }}=1.1 \mathrm{~V}$, the application of opposite potential greater than $1.1 \mathrm{~V}$ results into flow of electron from cathode to anode.
Reason : $\mathrm{Zn}$ is deposited at anode and $\mathrm{Cu}$ is dissolved at cathode.
- AIf both assertion and reason are true and reason is the correct explanation of the assertion
- Correct answerBIf both assertion and reason are true but reason is not the correct explanation of the assertion
- CIf assertion is true, but reason is false
- DBoth assertion and reason are false statements.
Solution
If the opposing potential becomes slightly larger than that of the cell, the direction of current flow is reversed, and so is the cell reaction. Now zine ions are converted to zine at one electrode and $\mathrm{Cu}$ is converted into copper ion and the overall cell reaction becomes
$$
\mathrm{Zn}^{2+}+\mathrm{Cu} \rightarrow \mathrm{Zn}+\mathrm{Cu}^{2+}
$$
Hence, the correct answer is option: 'B'.