What happens to the colour of litmus paper when a drop of acid falls on it ?

Options

A. colour fades
B. from blue it turns red
C. from red it turns blue
D. remains unchanged

Explanation

To answer the question, "What happens to the colour of litmus paper when a drop of acid falls on it?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Litmus Paper**: Litmus paper is a pH indicator used to determine whether a solution is acidic or basic. It comes in two colors: blue and red.

2. **Effect of Acid on Blue Litmus Paper**: When a drop of acid is placed on blue litmus paper, the blue paper changes its color to red. This indicates that the solution is acidic.

3. **Effect of Acid on Red Litmus Paper**: If a drop of acid is placed on red litmus paper, there is no change in color; the red litmus paper remains red. This shows that the red litmus paper is already indicating an acidic condition.

4. **Conclusion**: Therefore, the main effect of adding acid to litmus paper is that blue litmus paper turns red, while red litmus paper remains unchanged.

### Final Answer:
When a drop of acid falls on blue litmus paper, it turns red. Red litmus paper remains red when acid is added.

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