Assertion: pH of water increases on increasing temperature.
Reason: `H_(2)O rarr H^(+) + OH^(-)` is an exothermic process.

Options

A. Both assertion and reason are correct and reason is correct explanation of assertion.
B. Both assertion and reason are correct and reason is not correct explanation of assertion.
C. Assertion is true & reason is false.
D. Both assertion and reason are incorrect.

Explanation

To solve the question, we need to analyze the assertion and the reason provided:

**Assertion**: The pH of water increases on increasing temperature.
**Reason**: The dissociation of water (H₂O → H⁺ + OH⁻) is an exothermic process.

### Step-by-Step Solution:

1. **Understanding pH and Temperature**:
- pH is defined as \( \text{pH} = -\log[H^+] \), where \([H^+]\) is the concentration of hydrogen ions in solution.
- As temperature increases, the dissociation of water into \(H^+\) and \(OH^-\) ions occurs more readily.

2. **Equilibrium Constant and Temperature**:
- The dissociation of water can be represented as:
\[ H_2O \rightleftharpoons H^+ + OH^- \]
- The equilibrium constant \(K_w\) for this reaction is given by:
\[ K_w = [H^+][OH^-] \]
- As temperature increases, \(K_w\) also increases, indicating that the concentration of both \(H^+\) and \(OH^-\) ions increases.

3. **Effect on pH**:
- Since both \(H^+\) and \(OH^-\) ions increase with temperature, the concentration of \(H^+\) ions increases.
- An increase in \([H^+]\) leads to a decrease in pH, because pH is inversely related to the concentration of hydrogen ions.

4. **Evaluating the Assertion**:
- The assertion states that the pH of water increases with temperature. However, we have established that the pH actually decreases as temperature increases due to the increase in \([H^+]\).
- Therefore, the assertion is **false**.

5. **Evaluating the Reason**:
- The reason states that the dissociation of water is an exothermic process. However, the dissociation of water is actually an **endothermic** process, meaning it requires energy input to proceed.
- Therefore, the reason is also **false**.

6. **Conclusion**:
- Since both the assertion and the reason are false, the correct answer is that both the assertion and reason are incorrect.

### Final Answer:
**Option D**: Both assertion and reason are incorrect.