An acidic solution of copper (II) sulphate containing some contaiminations of zinc and iron (II) ions was electrolysed till all the copper is deposited. If electrolysis is further continued for sometime, the product liberated at cathode is

Options

A. `Fe`
B. `Zn`
C. `H_(2)`
D. Alloy of `Zn` and `Fe`

Explanation

To solve the problem, we need to analyze the electrolysis of an acidic solution of copper(II) sulfate (CuSO₄) containing zinc (Zn²⁺) and iron(II) (Fe²⁺) ions. We will determine what product is liberated at the cathode after all the copper has been deposited.

### Step-by-Step Solution:

1. **Identify the Components in the Solution:**
The solution contains:
- Copper ions (Cu²⁺)
- Zinc ions (Zn²⁺)
- Iron(II) ions (Fe²⁺)
- Hydrogen ions (H⁺) due to the acidic nature of the solution.

2. **Electrolysis Process:**
During electrolysis, the following reactions can occur:
- At the cathode, reduction takes place.
- The ions present in the solution can be reduced to form different products.

3. **Reduction Potentials:**
The standard reduction potentials (E°) for the relevant half-reactions are:
- Cu²⁺ + 2e⁻ → Cu (E° = +0.34 V)
- Zn²⁺ + 2e⁻ → Zn (E° = -0.76 V)
- Fe²⁺ + 2e⁻ → Fe (E° = -0.44 V)
- 2H⁺ + 2e⁻ → H₂ (E° = 0.00 V)

4. **Determine Which Species Gets Reduced:**
- Initially, Cu²⁺ ions are reduced at the cathode to deposit copper metal.
- After all the copper is deposited, we need to consider the remaining ions: Zn²⁺, Fe²⁺, and H⁺.
- Comparing the reduction potentials, H⁺ has the highest reduction potential (0.00 V), followed by Fe²⁺ (-0.44 V), and then Zn²⁺ (-0.76 V).

5. **Continuation of Electrolysis:**
- Since H⁺ has the highest reduction potential, it will be the next species to get reduced at the cathode after all the Cu has been deposited.
- The reduction reaction for H⁺ is:
\[ 2H^+ + 2e^- \rightarrow H_2(g) \]

6. **Conclusion:**
Therefore, after all the copper has been deposited, the product liberated at the cathode upon further electrolysis will be hydrogen gas (H₂).

### Final Answer:
The product liberated at the cathode is hydrogen gas (H₂).