Assertion `(A):` At the end of electrolysis using `Pt` electrodes, an aqueous solution of `CuSO_(4)` turns colourless.
Reason `(R): CuSO_(4)` changes to `Cu(OH)_(2)` during electrolysis.
(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.

Options

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.

Explanation

To solve the question, we will analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that at the end of electrolysis using platinum electrodes, an aqueous solution of CuSO₄ turns colorless.
- During electrolysis, copper ions (Cu²⁺) are reduced at the cathode, leading to the deposition of copper metal. This process removes copper ions from the solution, which contributes to the color change.

2. **Analyzing the Electrolysis Process**:
- At the cathode, Cu²⁺ ions gain electrons and are reduced to solid copper (Cu):
\[ \text{Cu}^{2+} + 2e^- \rightarrow \text{Cu (s)} \]
- At the anode, OH⁻ ions are oxidized to produce oxygen gas and water:
\[ 4\text{OH}^- \rightarrow 2\text{H}_2\text{O} + \text{O}_2 + 4e^- \]
- The remaining solution will contain sulfate ions (SO₄²⁻) and any leftover H⁺ ions from water, which do not contribute to color.

3. **Conclusion about Assertion (A)**:
- Since copper ions are being reduced and removed from the solution, the solution indeed turns colorless as the concentration of colored Cu²⁺ ions decreases.

4. **Understanding the Reason (R)**:
- The reason states that CuSO₄ changes to Cu(OH)₂ during electrolysis.
- This statement is incorrect because CuSO₄ does not convert to Cu(OH)₂ during the electrolysis process. Instead, Cu²⁺ ions are deposited as solid copper, and OH⁻ ions are involved in the oxidation reaction at the anode.

5. **Conclusion about Reason (R)**:
- The reason provided is incorrect as there is no formation of Cu(OH)₂ during the electrolysis of CuSO₄.

6. **Final Evaluation**:
- Since assertion (A) is correct and reason (R) is incorrect, the correct option is:
- **(c) If (A) is correct, but (R) is incorrect.**