Which compound is volatile on heating?

Options

A. `MgCl_2`
B. `HgCl_2`
C. `ZnCl_2`
D. None of these

Explanation

To determine which compound is volatile on heating, we need to analyze the options provided:

1. **MGCl2 (Magnesium Chloride)**:
- Magnesium chloride is a solid at room temperature. Upon heating, it does not readily vaporize or sublime; instead, it tends to decompose or melt without forming vapors. Therefore, it is not considered volatile.

2. **HGDCl2 (Mercuric Chloride)**:
- Mercuric chloride, also known as corrosive sublimate, is known for its volatility. On heating, it undergoes sublimation, meaning it transitions directly from a solid to a gas without passing through a liquid phase. This property makes it volatile.

3. **ZNCl2 (Zinc Chloride)**:
- Zinc chloride is also a solid at room temperature. While it can dissolve in water, it does not readily vaporize upon heating. Thus, it is not volatile.

4. **None of these**:
- This option suggests that none of the compounds listed are volatile, which we have already determined is incorrect since HGDCl2 is indeed volatile.

Based on the analysis above, the compound that is volatile on heating is **HGDCl2 (Mercuric Chloride)**.

### Step-by-Step Solution:
1. **Identify the compounds**: Look at the given options: MGCl2, HGDCl2, ZNCl2, and none of these.
2. **Understand volatility**: Define volatility as the ability of a substance to vaporize upon heating.
3. **Analyze each compound**:
- **MGCl2**: Not volatile; does not vaporize easily.
- **HGDCl2**: Volatile; sublimes upon heating.
- **ZNCl2**: Not volatile; does not vaporize easily.
4. **Conclusion**: The only compound that is volatile on heating is **HGDCl2**.