Which of the following compounds volatilises on heating

Options

A. `MgCl_(2)`
B. `HgCl_(2)`
C. `CaCl_(2)`
D. `FeCl_(3)`

Explanation

To determine which of the given compounds volatilizes on heating, we will analyze each option based on their chemical properties and states at room temperature.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- Magnesium chloride (MgCl2)
- Mercury chloride (HgCl2)
- Calcium chloride (CaCl2)
- Iron chloride (FeCl3)

2. **Understand Volatility**: A compound is considered volatile if it can easily convert from a solid or liquid state to a gas upon heating.

3. **Analyze Each Compound**:
- **Magnesium Chloride (MgCl2)**: This compound is typically a solid at room temperature and has a high melting point. It does not readily volatilize upon heating.
- **Mercury Chloride (HgCl2)**: This compound is known to sublimate, meaning it can transition from solid to gas without passing through a liquid phase when heated. It is also a liquid at certain temperatures, which contributes to its volatility.
- **Calcium Chloride (CaCl2)**: Similar to magnesium chloride, calcium chloride is a solid at room temperature and has a high melting point. It does not easily volatilize.
- **Iron Chloride (FeCl3)**: Iron chloride can be a solid at room temperature, and while it can decompose upon heating, it does not readily volatilize.

4. **Conclusion**: Among the options, **mercury chloride (HgCl2)** is the only compound that volatilizes upon heating due to its ability to sublimate and its physical state.

### Final Answer:
The compound that volatilizes on heating is **Mercury Chloride (HgCl2)**.

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