Which one of the following solutions will turn red litmus blue?

Options

A. Lemon juice
B. Acetic acid
C. Sodium hydroxide
D. Hydrochloric acid

Answer

To determine which solution will turn red litmus paper blue, we need to identify whether the solutions are acidic or basic. Here's a step-by-step solution:

### Step 1: Understand the role of litmus paper
Litmus paper is an indicator used to test whether a solution is acidic or basic. Red litmus paper turns blue in the presence of a base and remains red in the presence of an acid.

### Step 2: Identify the nature of the solutions
We need to analyze the solutions provided in the question. Common solutions include:
- Lemon juice
- Acetic acid
- Hydrochloric acid
- Sodium hydroxide

### Step 3: Classify the solutions
- **Lemon juice**: This is acidic due to citric acid.
- **Acetic acid**: This is also an acid (vinegar).
- **Hydrochloric acid**: This is a strong acid.
- **Sodium hydroxide**: This is a base.

### Step 4: Determine which solution will turn red litmus blue
Since red litmus paper turns blue in the presence of a base, we look for the only base among the options. Sodium hydroxide is the only base listed.

### Conclusion
The solution that will turn red litmus paper blue is **sodium hydroxide**.

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