A' is an aqueous acid , 'B' is an aqueous base. If they are diluted separately , then

Options

A. pH of A increases and pH of B decreases
B. pH of A increases and pH of B decreases till pH in each case is 7
C. pH of A and B increase
D. pH of B and A decrease

Answer

To solve the question regarding the effects of dilution on an aqueous acid (A) and an aqueous base (B), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Dilution**:
- When an acid or base is diluted, the volume of the solution increases while the number of moles of the acid or base remains constant.

2. **Effect of Dilution on Acid (A)**:
- For an aqueous acid, dilution leads to an increase in volume, which decreases the concentration of hydrogen ions (H⁺) in the solution.
- The relationship between pH and the concentration of H⁺ ions is given by the formula:
\[ \text{pH} = -\log[\text{H}^+] \]
- As the concentration of H⁺ decreases, the pH value increases.

3. **Effect of Dilution on Base (B)**:
- For an aqueous base, dilution also increases the volume, which decreases the concentration of hydroxide ions (OH⁻).
- The relationship between pOH and the concentration of OH⁻ ions is given by the formula:
\[ \text{pOH} = -\log[\text{OH}^-] \]
- As the concentration of OH⁻ decreases, the pOH value increases, which in turn affects the pH since:
\[ \text{pH} + \text{pOH} = 14 \]
- Therefore, if pOH increases, pH must decrease.

4. **Conclusion**:
- After dilution, the pH of the acid (A) increases, while the pH of the base (B) decreases.
- Hence, the correct answer is that the pH of A increases and the pH of B decreases.

### Final Answer:
- The pH of the acid (A) increases, and the pH of the base (B) decreases upon dilution.