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

Answer

To solve the question, "Which of the following metal on burning in moist air does not give smell of ammonia?", we will analyze the reactions of each metal with nitrogen and water (moist air) to determine if ammonia (NH3) is produced.

### Step-by-Step Solution:

1. **Understanding the Metals**:
- We need to analyze the behavior of the given metals (A, B, C, D) when they react with nitrogen (N2) in moist air.

2. **Reactions of Metals with Nitrogen**:
- Metals from Group 1 (alkali metals) and Group 2 (alkaline earth metals) can react with nitrogen to form nitrides.
- For example, magnesium (Mg) and calcium (Ca) will react with nitrogen to form their respective nitrides.

3. **Analyzing Each Metal**:
- **Option A: Magnesium (Mg)**
- Reaction:
\[ 3Mg + N2 \rightarrow Mg3N2 \]
- In moist air:
\[ Mg3N2 + 6H2O \rightarrow 3Mg(OH)2 + 2NH3 \]
- This produces ammonia (NH3), which has a smell.

- **Option B: Calcium (Ca)**
- Reaction:
\[ 3Ca + N2 \rightarrow Ca3N2 \]
- In moist air:
\[ Ca3N2 + 6H2O \rightarrow 3Ca(OH)2 + 2NH3 \]
- This also produces ammonia (NH3), which has a smell.

- **Option C: Potassium (K)**
- Reaction:
\[ 6K + N2 \rightarrow 2K3N \]
- In moist air:
- Potassium nitride does not readily react with water to produce ammonia.
- Thus, it does not produce a smell of ammonia.

- **Option D: Lithium (Li)**
- Reaction:
\[ 6Li + N2 \rightarrow 2Li3N \]
- In moist air:
\[ Li3N + 3H2O \rightarrow 3LiOH + NH3 \]
- This also produces ammonia (NH3), which has a smell.

4. **Conclusion**:
- From the analysis, potassium (Option C) is the only metal that does not produce ammonia when burned in moist air. Therefore, the answer is **C: Potassium**.