Which oxide will turn red litmus solution blue ?

Options

A. `MgO`
B. `SO_2`
C. `CO_2`
D. `NO_2`

Explanation

To determine which oxide will turn red litmus solution blue, we need to understand the properties of acids and bases, specifically how they interact with litmus paper.

### Step-by-Step Solution:

1. **Understanding Litmus Paper**:
- Litmus paper is a pH indicator used to test whether a solution is acidic or basic.
- Red litmus paper turns blue in basic solutions and remains red in acidic solutions.

2. **Identifying the Oxides**:
- The question provides several oxides:
- A) MgO (Magnesium oxide)
- B) SO2 (Sulfur dioxide)
- C) CO2 (Carbon dioxide)
- D) NO2 (Nitrogen dioxide)

3. **Analyzing Each Oxide**:
- **MgO (Magnesium Oxide)**:
- When MgO reacts with water, it forms magnesium hydroxide (Mg(OH)2), which is a base.
- Since it is basic, it will turn red litmus paper blue.

- **SO2 (Sulfur Dioxide)**:
- When SO2 reacts with water, it forms sulfurous acid (H2SO3), which is acidic.
- This will keep red litmus paper red.

- **CO2 (Carbon Dioxide)**:
- When CO2 reacts with water, it forms carbonic acid (H2CO3), which is also acidic.
- This will also keep red litmus paper red.

- **NO2 (Nitrogen Dioxide)**:
- When NO2 reacts with water, it forms nitric acid (HNO3), which is acidic.
- This will keep red litmus paper red as well.

4. **Conclusion**:
- Among the given options, only magnesium oxide (MgO) produces a basic solution when reacted with water, thus turning red litmus paper blue.
- Therefore, the correct answer is **A) MgO (Magnesium oxide)**.

### Final Answer:
The oxide that will turn red litmus solution blue is **Magnesium Oxide (MgO)**.

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