In which of the following electrolysis in aqueous medium, mass of anode decreases and `pH` of solution remains unchanged?

Options

A. Electrolysis of aqueous `AgNO_(3)` using silver anode and copper cathode
B. Electrolysis of aqeous `CuSO_(4)` using pure copper anode and impure copper cathode.
C. Electrolysis of aqeous `AgNO_(3)` using gold anode and silver cathode
D. Electrolysis of aqeous `CuSO_(4)` using silver anode and platium cathode.

Explanation

To solve the question regarding which electrolysis in aqueous medium results in a decrease in the mass of the anode while keeping the pH of the solution unchanged, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding the Electrolysis Process**:
- In electrolysis, oxidation occurs at the anode and reduction occurs at the cathode.
- The mass of the anode decreases if the material of the anode is oxidized to form cations that dissolve into the solution.

2. **Analyzing Each Option**:
- **Option A: Electrolysis of aqueous AgNO3 using silver anode and copper cathode**:
- At the anode: \( \text{Ag} \rightarrow \text{Ag}^+ + e^- \) (mass of anode decreases)
- At the cathode: \( \text{Ag}^+ + e^- \rightarrow \text{Ag} \) (Ag is deposited)
- The pH remains unchanged because there is no generation of H\(^+\) ions.
- **Conclusion**: Mass decreases, pH unchanged. This option is valid.

- **Option B: Electrolysis of CuSO4 using copper anode**:
- At the anode: \( \text{Cu} \rightarrow \text{Cu}^{2+} + 2e^- \) (mass of anode decreases)
- At the cathode: \( \text{Cu}^{2+} + 2e^- \rightarrow \text{Cu} \) (Cu is deposited)
- The pH remains unchanged because no H\(^+\) ions are produced.
- **Conclusion**: Mass decreases, pH unchanged. This option is valid.

- **Option C: Electrolysis of AgNO3 using gold anode and silver cathode**:
- At the anode: \( \text{O}_2 + 4H_2O + 4e^- \rightarrow 4OH^- \) (oxygen is evolved, mass of gold anode remains unchanged)
- At the cathode: \( \text{Ag}^+ + e^- \rightarrow \text{Ag} \) (Ag is deposited)
- The formation of OH\(^-\) ions increases the pH.
- **Conclusion**: Mass does not decrease, pH changes. This option is invalid.

- **Option D: Electrolysis of CuSO4 using silver anode and platinum cathode**:
- At the anode: \( \text{Ag} \rightarrow \text{Ag}^+ + e^- \) (mass of anode decreases)
- At the cathode: \( \text{Cu}^{2+} + 2e^- \rightarrow \text{Cu} \) (Cu is deposited)
- The pH remains unchanged because there is no generation of H\(^+\) ions.
- **Conclusion**: Mass decreases, pH unchanged. This option is valid.

3. **Final Conclusion**:
- The valid options where the mass of the anode decreases and the pH remains unchanged are **A, B, and D**.