X reacts with dilute nitric acid to form 'laughing gas' . What is X ?

Options

A. `Cu`
B. `P_4`
C. `S_8`
D. `Zn`

Answer

To determine the substance X that reacts with dilute nitric acid (HNO3) to produce 'laughing gas' (N2O), we can analyze the reactions of various substances with dilute nitric acid.

### Step-by-Step Solution:

1. **Identify 'Laughing Gas':**
- 'Laughing gas' is chemically known as nitrous oxide, with the formula N2O.

2. **Consider Possible Reactants:**
- We need to evaluate different substances (let's denote them as A, B, C, D, etc.) to see which one reacts with dilute HNO3 to produce N2O.

3. **Test Option A: Copper (Cu)**
- Reaction: \( Cu + 4HNO_3 \rightarrow Cu(NO_3)_2 + 2NO + 2H_2O \)
- Products: Copper nitrate, nitrogen monoxide (NO), and water.
- **Conclusion:** No N2O is produced. So, A is incorrect.

4. **Test Option B: Phosphorus (P4)**
- Reaction: \( P_4 + 10HNO_3 \rightarrow 4H_3PO_4 + 6NO_2 + 2H_2O \)
- Products: Phosphoric acid, nitrogen dioxide (NO2), and water.
- **Conclusion:** No N2O is produced. So, B is incorrect.

5. **Test Option C: Sulfur (S8)**
- Reaction: \( S_8 + 16HNO_3 \rightarrow 8H_2SO_4 + 8NO_2 + 4H_2O \)
- Products: Sulfuric acid, nitrogen dioxide (NO2), and water.
- **Conclusion:** No N2O is produced. So, C is incorrect.

6. **Test Option D: Zinc (Zn)**
- Reaction: \( Zn + 4HNO_3 \rightarrow Zn(NO_3)_2 + 2H_2O + N_2O \)
- Products: Zinc nitrate, water, and nitrous oxide (N2O).
- **Conclusion:** N2O is produced. So, D is correct.

7. **Final Answer:**
- The substance X that reacts with dilute nitric acid to form 'laughing gas' (N2O) is **Zinc (Zn)**.