Which of the following statements is correct about an aqueous solution of an acid and a base?
(i) higher the pH stronger the acid
(ii) Higher the pH, weaker the acid, (iii) Lower the pH, stronger the base ,(iv) Lower the pH, weaker the base

Options

A. (i) and (iii)
B. (ii) and (iii)
C. (i) and (iv)
D. (ii) and (iv)

Explanation

To determine which statements about an aqueous solution of an acid and a base are correct, we can analyze each option based on our understanding of the pH scale.

### Step-by-Step Solution:

1. **Understanding pH Scale**:
- The pH scale ranges from 0 to 14.
- A pH of 7 is neutral (pure water).
- pH values less than 7 indicate acidic solutions (stronger acids have lower pH values).
- pH values greater than 7 indicate basic solutions (stronger bases have higher pH values).

2. **Analyzing Each Statement**:
- **Statement (i)**: "Higher the pH stronger the acid."
- This is incorrect. Higher pH values indicate weaker acids. Strong acids have lower pH values.
- **Statement (ii)**: "Higher the pH, weaker the acid."
- This is correct. As pH increases, the acidity decreases, indicating a weaker acid.
- **Statement (iii)**: "Lower the pH, stronger the base."
- This is incorrect. Lower pH values indicate acidic solutions, not basic. Stronger bases correspond to higher pH values.
- **Statement (iv)**: "Lower the pH, weaker the base."
- This is correct. Lower pH values indicate stronger acids and thus a weaker base.

3. **Conclusion**:
- The correct statements are (ii) and (iv). Therefore, the answer to the question is that statements (ii) and (iv) are correct.

### Final Answer:
The correct statements about an aqueous solution of an acid and a base are:
- (ii) Higher the pH, weaker the acid.
- (iv) Lower the pH, weaker the base.