Which of the following give no residue on heating?

Options

A. `NH_(4)NO_(3)`
B. `NH_(4)NO_(2)`
C. `(NH_(4))_(2)Cr_(2)O_(7)`
D. `NH_(4)Cl`

Explanation

To determine which of the following compounds give no residue upon heating, we need to analyze the thermal decomposition of each compound listed in the options.

### Step-by-Step Solution:

1. **Analyze NH4NO3 (Ammonium Nitrate)**:
- Upon heating, ammonium nitrate decomposes to form nitrous oxide (N2O) and water (H2O).
- Reaction:
\[ 2 NH_4NO_3 \rightarrow N_2O + 2 H_2O \]
- Both products are gases, so there is no residue left after heating.

2. **Analyze NH4NO2 (Ammonium Nitrite)**:
- When ammonium nitrite is heated, it decomposes to form nitrogen gas (N2) and water (H2O).
- Reaction:
\[ NH_4NO_2 \rightarrow N_2 + 2 H_2O \]
- Again, both products are gases, resulting in no residue.

3. **Analyze (NH4)2Cr2O7 (Ammonium Dichromate)**:
- Upon heating, ammonium dichromate decomposes to form nitrogen gas (N2), chromium(III) oxide (Cr2O3), and water (H2O).
- Reaction:
\[ (NH_4)_2Cr_2O_7 \rightarrow N_2 + Cr_2O_3 + 4 H_2O \]
- Here, Cr2O3 is a solid residue, meaning this compound does leave a residue upon heating.

4. **Analyze NH4Cl (Ammonium Chloride)**:
- When ammonium chloride is heated, it decomposes to form ammonia gas (NH3) and hydrogen chloride gas (HCl).
- Reaction:
\[ NH_4Cl \rightarrow NH_3 + HCl \]
- Both products are gases, so there is no residue left after heating.

### Conclusion:
The compounds that give no residue upon heating are:
- NH4NO3 (Option 1)
- NH4NO2 (Option 2)
- NH4Cl (Option 4)

Thus, the final answer is **Options 1, 2, and 4**.