Ammonia gas can evolve by heating :

Options

A. `NaNO_3` with zinc dust and sodium hydroxide
B. `NaNO_2` with dil `HNO_3`
C. dry `(NH_4)_2Cr_2O_7`
D. ammonium chloride with lime water

Explanation

### Step-by-Step Solution

1. **Understanding the Question**: The question asks which reactions can produce ammonia gas (NH3) upon heating.

2. **Analyzing the First Reaction**:
- Reaction: NaNO3 + Zn + NaOH → NH3 + Na2ZnO2 + H2O
- Upon heating, this reaction produces ammonia.
- **Conclusion**: This reaction evolves ammonia gas.

3. **Analyzing the Second Reaction**:
- Reaction: NaNO2 + HNO3 → NaNO3 + NO2 + NO + H2O
- This reaction does not produce ammonia gas.
- **Conclusion**: This reaction does not evolve ammonia gas.

4. **Analyzing the Third Reaction**:
- Reaction: (NH4)2Cr2O7 (ammonium dichromate) → N2 + 4H2O + Cr2O3 upon heating.
- This reaction does not produce ammonia gas.
- **Conclusion**: This reaction does not evolve ammonia gas.

5. **Analyzing the Fourth Reaction**:
- Reaction: NH4Cl + Ca(OH)2 (lime water) → NH3 + H2O + CaCl2 upon heating.
- This reaction produces ammonia gas.
- **Conclusion**: This reaction evolves ammonia gas.

6. **Final Conclusion**:
- The reactions that evolve ammonia gas upon heating are:
- Option 1: NaNO3 + Zn + NaOH
- Option 4: NH4Cl + Ca(OH)2

### Final Answer
The correct options are 1 and 4.

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