Which metals upon heating in presence of air followed by hydrolysis gives ammonia.

Options

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

Explanation

To solve the question of which metals upon heating in the presence of air followed by hydrolysis give ammonia, we will analyze each option step by step.

### Step 1: Analyze Lithium
1. **Heating Lithium in Air**: When lithium is heated in the presence of air (which contains nitrogen), it reacts with nitrogen to form lithium nitride (Li3N).
- **Reaction**:
\[ 6Li + N_2 \rightarrow 2Li_3N \]

2. **Hydrolysis of Lithium Nitride**: When lithium nitride undergoes hydrolysis, it reacts with water to produce lithium hydroxide and ammonia.
- **Reaction**:
\[ Li_3N + 3H_2O \rightarrow 3LiOH + NH_3 \]

3. **Conclusion for Lithium**: Lithium gives ammonia upon heating in air followed by hydrolysis.

### Step 2: Analyze Potassium
1. **Heating Potassium in Air**: Potassium does not react with nitrogen in the air to form potassium nitride because potassium nitride is not stable.

2. **Conclusion for Potassium**: Potassium does not produce ammonia.

### Step 3: Analyze Rubidium and Magnesium
1. **Heating Rubidium in Air**: Similar to potassium, rubidium does not react with nitrogen in the air to form rubidium nitride.

2. **Heating Magnesium in Air**: Magnesium reacts with nitrogen to form magnesium nitride (Mg3N2).
- **Reaction**:
\[ 3Mg + N_2 \rightarrow Mg_3N_2 \]

3. **Hydrolysis of Magnesium Nitride**: When magnesium nitride undergoes hydrolysis, it produces magnesium hydroxide and ammonia.
- **Reaction**:
\[ Mg_3N_2 + 6H_2O \rightarrow 3Mg(OH)_2 + 2NH_3 \]

4. **Conclusion for Magnesium**: Magnesium gives ammonia upon heating in air followed by hydrolysis.

### Step 4: Analyze Calcium and Potassium
1. **Heating Calcium in Air**: Calcium reacts with nitrogen to form calcium nitride (Ca3N2).
- **Reaction**:
\[ 3Ca + N_2 \rightarrow Ca_3N_2 \]

2. **Hydrolysis of Calcium Nitride**: When calcium nitride undergoes hydrolysis, it produces calcium hydroxide and ammonia.
- **Reaction**:
\[ Ca_3N_2 + 6H_2O \rightarrow 3Ca(OH)_2 + 2NH_3 \]

3. **Conclusion for Calcium**: Calcium gives ammonia upon heating in air followed by hydrolysis.

4. **Conclusion for Potassium**: As previously established, potassium does not produce ammonia.

### Final Conclusion:
- **Correct Options**:
- Lithium and Magnesium both produce ammonia.
- Therefore, the correct answer is **Option 3: Lithium-Magnesium**.