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Assertion(A): Whne acidified ZnSO(4) sol...

Assertion`(A):` Whne acidified `ZnSO_(4)` solution is electrolyzed between `Zn` electrodes, it is `Zn` that is deposited at the cathode and `H_(2)(g)` is not evolved.
Reason `(R):` The electrode potential of `Zn` is more negative than hydrogen as the overpotential for hydrogen evolution in `Zn` is quite large.

A

If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`.

B

If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`.

C

If `(A)` is correct, but `(R)` is incorrect.

D

If `(A)` is incorrect, `(R)` is correct.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question, we need to analyze both the assertion and the reason provided. ### Step-by-step Solution: 1. **Understanding the Electrolysis Process**: - When an acidified solution of ZnSO4 is electrolyzed, we have Zn²⁺ ions and H⁺ ions present in the solution. The electrolysis occurs between two zinc electrodes. 2. **Identifying the Electrodes**: - The cathode is the electrode where reduction occurs, and the anode is where oxidation occurs. In this case, both electrodes are zinc. 3. **Reduction Reactions at the Cathode**: - At the cathode, two possible reduction reactions can occur: - Reduction of Zn²⁺ ions: \[ \text{Zn}^{2+} + 2e^- \rightarrow \text{Zn (s)} \] - Reduction of H⁺ ions: \[ 2\text{H}^+ + 2e^- \rightarrow \text{H}_2(g) \] 4. **Comparing Standard Reduction Potentials**: - The standard reduction potential for Zn²⁺/Zn is -0.76 V. - The standard reduction potential for H⁺/H₂ is 0.00 V. - Since the standard reduction potential for H⁺ is higher (less negative) than that for Zn²⁺, hydrogen ions are more likely to be reduced to hydrogen gas. 5. **Considering Overpotential**: - The overpotential for hydrogen evolution on zinc is significant. This means that even though H⁺ ions have a higher reduction potential, the actual discharge of H⁺ may be hindered due to the overpotential, making Zn deposition more favorable under certain conditions. 6. **Conclusion**: - The assertion states that Zn is deposited at the cathode and H₂ is not evolved, which is incorrect because, under standard conditions, H₂ gas would be evolved. - The reason states that the electrode potential of Zn is more negative than that of hydrogen and that the overpotential for hydrogen evolution is quite large, which is true. ### Final Answer: - The assertion (A) is **false** and the reason (R) is **true**. Therefore, the correct conclusion is that the assertion is incorrect while the reason is correct.
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