The gas which is highly soluble in water and turns red litmus blue is

Options

A. `N_2`
B. `SO_2`
C. `NH_3`
D. `O_2`

Explanation

To solve the question "The gas which is highly soluble in water and turns red litmus blue is," we can follow these steps:

### Step 1: Identify the Properties of the Gas
We need to find a gas that is:
1. Highly soluble in water.
2. Capable of turning red litmus paper blue.

### Step 2: Understand the Concept of Litmus Paper
Litmus paper is used to test the acidity or basicity of a solution:
- Red litmus paper turns blue in the presence of a base.
- Blue litmus paper turns red in the presence of an acid.

### Step 3: Consider Common Gases
Common gases that are soluble in water include:
- Ammonia (NH3)
- Carbon dioxide (CO2)
- Hydrogen chloride (HCl)
- Sulfur dioxide (SO2)

### Step 4: Analyze Each Gas
- **Ammonia (NH3)**:
- Highly soluble in water.
- Forms ammonium hydroxide (NH4OH) when dissolved, which is a base. This will turn red litmus paper blue.

- **Carbon dioxide (CO2)**:
- Soluble in water but forms carbonic acid (H2CO3), which is acidic and would turn blue litmus paper red.

- **Hydrogen chloride (HCl)**:
- Highly soluble in water and forms hydrochloric acid, which is also acidic and would turn blue litmus paper red.

- **Sulfur dioxide (SO2)**:
- Soluble in water and forms sulfurous acid (H2SO3), which is acidic and would turn blue litmus paper red.

### Step 5: Conclusion
From the analysis, the only gas that is highly soluble in water and turns red litmus blue is **Ammonia (NH3)**.

### Final Answer
The gas which is highly soluble in water and turns red litmus blue is **Ammonia (NH3)**.

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