Which of the following metal can replace zinc from `ZnSO_4` solution?

Options

A. Cu
B. Hg
C. Fe
D. A1

Explanation

To determine which metal can replace zinc from a `ZnSO_4` solution, we need to analyze the reduction potentials of the metals in question. The ability of a metal to displace another metal from its salt solution is based on their respective reduction potentials, as outlined in the electrochemical series.

### Step-by-Step Solution:

1. **Identify the Reduction Potential of Zinc**:
- The reduction half-reaction for zinc is:
\[ \text{Zn}^{2+} + 2e^- \rightarrow \text{Zn} \quad \text{(E° = -0.76 V)} \]
- This indicates that zinc has a relatively low tendency to be reduced, making it a good reducing agent.

2. **List the Reduction Potentials of Other Metals**:
- For comparison, we need the reduction potentials of other metals:
- Copper:
\[ \text{Cu}^{2+} + 2e^- \rightarrow \text{Cu} \quad \text{(E° = +0.33 V)} \]
- Mercury:
\[ \text{Hg}^{2+} + 2e^- \rightarrow \text{Hg} \quad \text{(E° = +0.85 V)} \]
- Iron:
\[ \text{Fe}^{2+} + 2e^- \rightarrow \text{Fe} \quad \text{(E° = -0.44 V)} \]
- Aluminum:
\[ \text{Al}^{3+} + 3e^- \rightarrow \text{Al} \quad \text{(E° = -1.66 V)} \]

3. **Compare the Reduction Potentials**:
- The more negative the reduction potential, the stronger the reducing agent. Thus, we compare the potentials:
- Zinc: -0.76 V
- Copper: +0.33 V
- Mercury: +0.85 V
- Iron: -0.44 V
- Aluminum: -1.66 V

4. **Determine Which Metal Can Replace Zinc**:
- A metal can replace another in a solution if it has a higher (more positive) reduction potential than the metal in the solution.
- In this case, both copper (+0.33 V) and mercury (+0.85 V) have higher reduction potentials than zinc (-0.76 V), meaning they can replace zinc in the `ZnSO_4` solution.

5. **Conclusion**:
- Among the metals listed, **copper (Cu)** and **mercury (Hg)** can replace zinc from the `ZnSO_4` solution. However, aluminum cannot replace zinc because it has a more negative reduction potential (-1.66 V).

### Final Answer:
Copper (Cu) and Mercury (Hg) can replace zinc from `ZnSO_4` solution.