How many compounds liberate `NH_(3)` on heating from the following ?
`(NH_(4))_(2)SO_(4),(NH_(4))_(2)CO_(3),NH_(4)Cl,NH_(4)NO_(3),(NH_(4))_(2)Cr_(2)O_(7)`

Explanation

To determine how many compounds liberate `NH3` on heating from the given list, we will analyze each compound step by step.

### Step-by-Step Solution:

1. **Analyze Ammonium Sulfate `(NH4)2SO4`:**
- When ammonium sulfate is heated, it decomposes to form ammonia and ammonium hydrogen sulfate.
- **Reaction:**
\[ (NH_4)_2SO_4 \rightarrow NH_3 + NH_4HSO_4 \]
- **Conclusion:** Ammonium sulfate liberates `NH3` on heating.

2. **Analyze Ammonium Carbonate `(NH4)2CO3`:**
- Upon heating, ammonium carbonate decomposes to produce ammonia, water, and carbon dioxide.
- **Reaction:**
\[ (NH_4)_2CO_3 \rightarrow NH_3 + H_2O + CO_2 \]
- **Conclusion:** Ammonium carbonate liberates `NH3` on heating.

3. **Analyze Ammonium Chloride `NH4Cl`:**
- When ammonium chloride is heated, it decomposes to form ammonia and hydrochloric acid.
- **Reaction:**
\[ NH_4Cl \rightarrow NH_3 + HCl \]
- **Conclusion:** Ammonium chloride liberates `NH3` on heating.

4. **Analyze Ammonium Nitrate `NH4NO3`:**
- Heating ammonium nitrate results in the formation of nitrous oxide and water, without producing ammonia.
- **Reaction:**
\[ NH_4NO_3 \rightarrow N_2O + H_2O \]
- **Conclusion:** Ammonium nitrate does not liberate `NH3` on heating.

5. **Analyze Ammonium Dichromate `(NH4)2Cr2O7`:**
- Upon heating, ammonium dichromate decomposes to form nitrogen gas, chromium(III) oxide, and water, without producing ammonia.
- **Reaction:**
\[ (NH_4)_2Cr_2O_7 \rightarrow N_2 + Cr_2O_3 + H_2O \]
- **Conclusion:** Ammonium dichromate does not liberate `NH3` on heating.

### Final Count:
- The compounds that liberate `NH3` on heating are:
1. Ammonium sulfate `(NH4)2SO4`
2. Ammonium carbonate `(NH4)2CO3`
3. Ammonium chloride `NH4Cl`

Thus, **3 compounds** liberate `NH3` on heating.

### Summary:
The answer is **3 compounds** liberate `NH3` on heating.