Which of the following is the most suitable drying agent for ammonia gas

Options

A. Calcium oxide
B. Anhydrous calcium chloride
C. Phosphorus pentoxide
D. Conc. sulphuric acid

Explanation

To determine the most suitable drying agent for ammonia gas (NH3), we need to analyze the properties of various drying agents and their interactions with ammonia.

### Step-by-Step Solution:

1. **Identify the Drying Agents**: The options given for drying agents include:
- Calcium oxide (CaO)
- Calcium chloride (CaCl2)
- Phosphorus pentoxide (P2O5)
- Sulfuric acid (H2SO4)

2. **Understand the Function of a Drying Agent**: A drying agent is a substance that absorbs moisture from gases or liquids. For a drying agent to be effective for ammonia, it should not react chemically with ammonia.

3. **Analyze Each Drying Agent**:
- **Calcium Oxide (CaO)**: This is a strong drying agent that does not react with ammonia. It simply absorbs water vapor, making it suitable for drying ammonia gas.
- **Calcium Chloride (CaCl2)**: This compound can react with ammonia, forming ammonium chloride (NH4Cl), which makes it unsuitable as a drying agent for ammonia.
- **Phosphorus Pentoxide (P2O5)**: Although it is a powerful dehydrating agent, it can also react with ammonia, forming phosphoric acid and other compounds, thus it is not suitable.
- **Sulfuric Acid (H2SO4)**: While concentrated sulfuric acid is a good drying agent, it can react with ammonia to form ammonium sulfate, making it ineffective for drying ammonia gas.

4. **Conclusion**: Since calcium oxide does not react with ammonia and effectively absorbs moisture, it is the most suitable drying agent for ammonia gas.

### Final Answer:
The most suitable drying agent for ammonia gas is **Calcium Oxide (CaO)**.