When the temperature of reactions will increase then the effect on pH value will

Options

A. increase
B. decrease
C. first increases then decrease
D. remains same

Explanation

To solve the question regarding the effect of temperature on the pH value of a solution, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding pH**:
- pH is defined as the negative logarithm of the concentration of hydrogen ions (H⁺) in a solution.
- The formula for pH is:
\[ \text{pH} = -\log[\text{H}^+] \]

2. **Effect of Temperature on Water Dissociation**:
- When the temperature of a solution increases, the dissociation of water (H₂O) into hydrogen ions (H⁺) and hydroxide ions (OH⁻) also increases.
- The reaction can be represented as:
\[ \text{H}_2\text{O} \rightleftharpoons \text{H}^+ + \text{OH}^- \]

3. **Increase in H⁺ Ion Concentration**:
- As temperature rises, more water molecules dissociate, leading to an increase in the concentration of H⁺ ions in the solution.

4. **Impact on pH**:
- Since pH is inversely related to the concentration of H⁺ ions, an increase in H⁺ concentration will result in a decrease in pH.
- This means that as the temperature increases and H⁺ concentration rises, the pH value will drop.

5. **Conclusion**:
- Therefore, when the temperature of the reaction increases, the pH value will decrease.

### Final Answer:
- The correct answer is that the pH value will **decrease** when the temperature of the reaction increases.