Which of the following aqueous solution produces metal after electrolysis?

Options

A. `K_2Cr_2O_7`
B. `KMnO_4`
C. `CH_3COONa`
D. `CuCl_2`

Answer

To determine which aqueous solution produces a metal after electrolysis, we need to analyze the electrochemical behavior of the ions present in each solution.

### Step-by-Step Solution:

1. **Identify the Solutions**: The question provides several aqueous solutions. We need to identify the metal ions present in each solution.

2. **Understand Electrolysis**: During electrolysis, reduction occurs at the cathode (negative electrode), where cations gain electrons to form neutral metals.

3. **Consider Water's Role**: In aqueous solutions, water dissociates into H⁺ and OH⁻ ions. The presence of H⁺ ions means that hydrogen gas can also be produced at the cathode if no other metal ions can be reduced more easily.

4. **Electrode Potentials**: Each metal ion has a specific standard electrode potential. The more positive the electrode potential, the easier it is for that ion to be reduced. We will compare the electrode potentials of the metal ions in the given solutions.

5. **Evaluate Each Solution**:
- **Potassium Dichromate (K₂Cr₂O₇)**: Contains K⁺ ions. The reduction potential for K⁺ is -2.93 V.
- **Potassium Permanganate (KMnO₄)**: Contains K⁺ ions. The reduction potential is also -2.93 V.
- **Sodium Acetate (CH₃COONa)**: Contains Na⁺ ions. The reduction potential for Na⁺ is -2.71 V.
- **Copper(II) Chloride (CuCl₂)**: Contains Cu²⁺ ions. The reduction potential for Cu²⁺ is +0.34 V.

6. **Determine the Most Favorable Reduction**: Among the ions present, Cu²⁺ has the highest (most positive) reduction potential. Therefore, it will be reduced to form copper metal at the cathode.

7. **Conclusion**: The aqueous solution that produces a metal after electrolysis is Copper(II) Chloride (CuCl₂), which will deposit copper metal at the cathode.

### Final Answer:
The correct answer is **D) CuCl₂**.

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