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

**Step-by-Step Solution:**

1. **Understanding the Components:**
- Let’s denote the aqueous acid as A (HA) and the aqueous base as B (BOH).
- When diluted, the acid will dissociate into H⁺ (hydronium ions) and A⁻ (conjugate base), while the base will dissociate into B⁺ (cations) and OH⁻ (hydroxide ions).

2. **Dilution of Acid (A):**
- When the acid is diluted, the concentration of H⁺ ions decreases.
- The pH of a solution is calculated using the formula:
\[ \text{pH} = -\log[\text{H}^+] \]
- As the concentration of H⁺ ions decreases, the pH increases. This indicates that the solution becomes less acidic.

3. **Dilution of Base (B):**
- When the base is diluted, the concentration of OH⁻ ions also decreases.
- The relationship between pH and pOH is given by:
\[ \text{pH} + \text{pOH} = 14 \]
- As the concentration of OH⁻ decreases, the pOH increases, which means the pH decreases. This indicates that the solution becomes less basic.

4. **Final Observations:**
- After dilution:
- The pH of the acid (A) increases (becomes less acidic).
- The pH of the base (B) decreases (becomes less basic).
- Both pH values will approach 7 but will not reach it exactly.

5. **Conclusion:**
- Therefore, the correct option is that the pH of A will increase and the pH of B will decrease.