In which of the following reactions `NH_(3)` gas evolution occurs?

Options

A. `NO_(3)^(-)+Zn+dil.H_(2)SO_(4) overset(warm)to`
B. `NH_(4)^(+)"salt"+NaOH overset(Delta)to`
C. `AlN+"steam"to`
D. `CH_(3)COONH_(3)overset(Delta)to`

Explanation

To determine in which of the following reactions NH₃ gas evolution occurs, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Option 1: NH₃ formation and neutralization**
- The reaction involves the formation of NH₃ which is then neutralized to NH₄⁺ by H₂SO₄.
- Since NH₃ is being converted to NH₄⁺ and not liberated as a gas, there is no NH₃ gas evolution in this reaction.
- **Conclusion**: This option is incorrect.

2. **Option 2: NH₄Cl + NaOH on heating**
- The reaction is: NH₄Cl + NaOH → NH₃ (gas) + NaCl + H₂O.
- Upon heating, NH₄Cl reacts with NaOH to produce NH₃ gas along with NaCl and water.
- **Conclusion**: This option is correct as NH₃ gas is evolved.

3. **Option 3: AlN + steam**
- The reaction is: AlN + 3H₂O → Al₂O₃ + 2NH₃ (gas).
- Here, aluminum nitride (AlN) reacts with steam to produce aluminum oxide and NH₃ gas.
- **Conclusion**: This option is also correct as NH₃ gas is evolved.

4. **Option 4: CH₃COONH₄ on heating**
- The reaction is: CH₃COONH₄ → CH₃COOH + NH₃ (gas).
- When ammonium acetate (CH₃COONH₄) is heated, it decomposes to form acetic acid and NH₃ gas.
- **Conclusion**: This option is correct as NH₃ gas is evolved.

### Final Conclusion:
The reactions in which NH₃ gas evolution occurs are:
- **Option 2**: NH₄Cl + NaOH on heating
- **Option 3**: AlN + steam
- **Option 4**: CH₃COONH₄ on heating

Thus, the correct options are 2, 3, and 4.

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