Which of the following metal on burning in moist air does not give smell of ammonia?

Options

A. Mg
B. Ca
C. K
D. Li

Explanation

To determine which metal does not give the smell of ammonia when burned in moist air, we will analyze the reactions of each metal with nitrogen and water.

### Step-by-Step Solution:

1. **Understanding the Components**:
- In moist air, there are two key components: nitrogen (N2) and water (H2O).
- When metals react with these components, they can form metal nitrides and hydroxides, which may release ammonia (NH3).

2. **Analyzing Each Metal**:
- **Magnesium (Mg)**:
- Reaction with nitrogen:
\[ 3Mg + N_2 \rightarrow Mg_3N_2 \]
- Reaction with water:
\[ Mg_3N_2 + 6H_2O \rightarrow 3Mg(OH)_2 + 2NH_3 \]
- Result: Produces ammonia (NH3), which gives a smell of ammonia.

- **Calcium (Ca)**:
- Reaction with nitrogen:
\[ 3Ca + N_2 \rightarrow Ca_3N_2 \]
- Reaction with water:
\[ Ca_3N_2 + 6H_2O \rightarrow 3Ca(OH)_2 + 2NH_3 \]
- Result: Produces ammonia (NH3), which gives a smell of ammonia.

- **Lithium (Li)**:
- Reaction with nitrogen:
\[ 6Li + N_2 \rightarrow 2Li_3N \]
- Reaction with water:
\[ Li_3N + 3H_2O \rightarrow 3LiOH + NH_3 \]
- Result: Produces ammonia (NH3), which gives a smell of ammonia.

- **Potassium (K)**:
- Reaction with nitrogen:
- Potassium does not react significantly with nitrogen at room temperature.
- Therefore, it does not form a nitride.
- When potassium reacts with water, it forms potassium hydroxide (KOH) without producing ammonia:
\[ 2K + 2H_2O \rightarrow 2KOH + H_2 \]
- Result: Does not produce ammonia, hence no smell of ammonia.

3. **Conclusion**:
- Among the metals analyzed, only potassium does not produce ammonia when burned in moist air.

### Final Answer:
The metal that does not give a smell of ammonia when burned in moist air is **Potassium (K)**.