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 solve the question of which metal, when burned in moist air, does not produce the smell of ammonia, we will analyze the reactions of each of the given metals with nitrogen and water vapor present in moist air.

### Step-by-Step Solution:

1. **Identify the Metals**: The metals given are magnesium (Mg), calcium (Ca), potassium (K), and lithium (Li).

2. **Understand the Concept of Moist Air**: Moist air contains both nitrogen (N₂) and water vapor (H₂O). The reactions of metals with these components will determine if ammonia (NH₃) is produced.

3. **Reaction of Magnesium with Moist Air**:
- Magnesium reacts with nitrogen to form magnesium nitride (Mg₃N₂).
- When magnesium nitride reacts with water (from moist air), it produces magnesium hydroxide (Mg(OH)₂) and ammonia (NH₃).
- **Conclusion**: Magnesium produces ammonia.

4. **Reaction of Calcium with Moist Air**:
- Calcium reacts with nitrogen to form calcium nitride (Ca₃N₂).
- When calcium nitride reacts with water, it forms calcium hydroxide (Ca(OH)₂) and ammonia (NH₃).
- **Conclusion**: Calcium produces ammonia.

5. **Reaction of Potassium with Moist Air**:
- Potassium does not react with nitrogen under normal conditions.
- Since there is no reaction with nitrogen, potassium does not produce ammonia when burned in moist air.
- **Conclusion**: Potassium does not produce ammonia.

6. **Reaction of Lithium with Moist Air**:
- Lithium reacts with nitrogen to form lithium nitride (Li₃N).
- When lithium nitride reacts with water, it produces lithium hydroxide (LiOH) and ammonia (NH₃).
- **Conclusion**: Lithium produces ammonia.

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

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

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