Ammonia gas can not be dried over

Options

A. Quick lime
B. Conc `H_(2)SO_(4)`
C. `P_(2)O_(5)`
D. `CaCl_(2)`

Answer

### Step-by-Step Solution:

1. **Understanding the Properties of Ammonia:**
- Ammonia (NH₃) is a basic gas that can react with acids and certain compounds.

2. **Identifying Drying Agents:**
- Common drying agents include quick lime (calcium oxide), concentrated sulfuric acid, phosphorous pentoxide (P₂O₅), and calcium chloride (CaCl₂).

3. **Quick Lime as a Drying Agent:**
- Quick lime can absorb moisture to form calcium hydroxide (Ca(OH)₂) without reacting with ammonia.
- Since both quick lime and ammonia are basic, they do not react with each other.

4. **Concentrated Sulfuric Acid:**
- Concentrated sulfuric acid is an acidic compound. When ammonia is passed over it, a chemical reaction occurs:
\[ \text{NH}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{(NH}_4)_2\text{SO}_4 \]
- This reaction produces ammonium sulfate, indicating that ammonia cannot be dried over concentrated sulfuric acid.

5. **Phosphorous Pentoxide:**
- Phosphorous pentoxide is also an acidic oxide. When ammonia interacts with it, the following reaction occurs:
\[ \text{NH}_3 + \text{P}_2\text{O}_5 \rightarrow \text{(NH}_4)_3\text{PO}_4 \]
- This reaction forms ammonium phosphate, which shows that ammonia cannot be dried over phosphorous pentoxide.

6. **Calcium Chloride:**
- Calcium chloride is another drying agent that can absorb moisture. However, it can react with ammonia to form ammonium chloride:
\[ \text{NH}_3 + \text{CaCl}_2 + \text{H}_2\text{O} \rightarrow \text{NH}_4\text{Cl} + \text{Ca(OH)}_2 \]
- This indicates that ammonia cannot be dried over calcium chloride either.

7. **Conclusion:**
- Therefore, ammonia gas cannot be dried over concentrated sulfuric acid, phosphorous pentoxide, or calcium chloride due to the chemical reactions that occur. The only drying agent that does not react with ammonia is quick lime.

### Final Answer:
Ammonia gas cannot be dried over concentrated sulfuric acid, phosphorous pentoxide, or calcium chloride due to their reactivity with ammonia.

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