An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?

Options

A. Baking powder
B. Lime
C. Ammonium hydroxide solution
D. Hydrochloric acid

Explanation

To solve the question, we need to determine which solution can reverse the change of an aqueous solution that turns red litmus blue. This indicates that the solution is basic in nature. To reverse this change, we need to add an acidic solution. Here’s the step-by-step solution:

### Step-by-Step Solution:

1. **Identify the Nature of the Aqueous Solution:**
- The aqueous solution turns red litmus blue, which indicates that the solution is basic (alkaline).

2. **Understand the Color Change of Litmus:**
- Red litmus paper turns blue in the presence of a base. Conversely, blue litmus paper turns red in the presence of an acid.

3. **Determine the Required Action:**
- To reverse the change from blue back to red, we need to add an acid to the basic solution.

4. **Select the Appropriate Acid:**
- Among the options provided (not specified in the question), we need to choose a solution that is acidic. Common examples include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), or acetic acid (CH₃COOH).

5. **Conclusion:**
- Adding an excess of hydrochloric acid (HCl) will effectively reverse the change, turning the blue litmus back to red.

### Final Answer:
Excess addition of hydrochloric acid (HCl) would reverse the change.

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