Chlorine gas is not produced by heating:

Options

A. `SOCl_(2)`
B. `PbCl_(4)`
C. `FeCl_(3)`
D. `Hg_(2)Cl_(2)`

Explanation

To solve the question of which compound does not produce chlorine gas when heated, we will analyze each of the given compounds step by step.

### Step-by-Step Solution:

1. **Identify the Compounds**: We need to evaluate the following compounds:
- SOCl2 (Thionyl Chloride)
- PbCl4 (Lead Tetrachloride)
- FeCl3 (Iron Chloride)
- Hg2Cl2 (Mercury(I) Chloride)

2. **Analyze SOCl2 (Thionyl Chloride)**:
- When SOCl2 is heated, it decomposes into sulfur dioxide (SO2) and chlorine gas (Cl2).
- **Reaction**: SOCl2 → SO2 + Cl2
- **Conclusion**: Chlorine gas is produced.

3. **Analyze PbCl4 (Lead Tetrachloride)**:
- When PbCl4 is heated, it decomposes into lead chloride (PbCl2) and chlorine gas (Cl2).
- **Reaction**: PbCl4 → PbCl2 + Cl2
- **Conclusion**: Chlorine gas is produced.

4. **Analyze FeCl3 (Iron Chloride)**:
- When FeCl3 is heated, it can decompose to form iron (Fe) and chlorine gas (Cl2).
- **Reaction**: 2FeCl3 → 2Fe + 3Cl2
- **Conclusion**: Chlorine gas is produced.

5. **Analyze Hg2Cl2 (Mercury(I) Chloride)**:
- When Hg2Cl2 is heated, it decomposes to form mercury (Hg) and mercury(II) chloride (HgCl2).
- **Reaction**: Hg2Cl2 → 2Hg + Cl2
- **Conclusion**: Chlorine gas is not produced.

6. **Final Conclusion**:
- Among the compounds analyzed, Hg2Cl2 (Mercury(I) Chloride) does not produce chlorine gas when heated.
- Therefore, the correct answer is **Hg2Cl2**.