Answer the following questions with respect to the solutions marked 'A' and 'B' having pH values 4 and 10 respectively.
Which solution will change red litmus blue?

Answer

To determine which solution will change red litmus paper to blue, we need to analyze the pH values of the solutions marked 'A' and 'B'.

### Step-by-Step Solution:

1. **Identify the pH Values**:
- Solution A has a pH of 4.
- Solution B has a pH of 10.

2. **Understand pH Scale**:
- The pH scale ranges from 0 to 14.
- A pH less than 7 indicates an acidic solution.
- A pH of 7 is neutral.
- A pH greater than 7 indicates a basic (alkaline) solution.

3. **Classify the Solutions**:
- Since solution A has a pH of 4, it is acidic.
- Since solution B has a pH of 10, it is basic.

4. **Know the Behavior of Litmus Paper**:
- Red litmus paper turns blue in the presence of a basic solution.
- Red litmus paper remains red in acidic solutions.

5. **Determine the Effect on Red Litmus Paper**:
- When red litmus paper is placed in solution A (pH 4), it will remain red because it is acidic.
- When red litmus paper is placed in solution B (pH 10), it will turn blue because it is basic.

6. **Conclusion**:
- Therefore, the solution that will change red litmus paper to blue is solution B.

### Final Answer:
Solution B will change red litmus blue.

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