Gypsum on heating at 393K produces

Options

A. dead burnt plaster
B. Anhydrous `CaSO_4`
C. `CaSO_4 . 1/2 H_(2)O`
D. `CaSO_4 . 5 H_(2)O`

Explanation

To solve the question regarding the products formed when gypsum is heated at 393 K, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chemical Formula of Gypsum**:
Gypsum is chemically represented as \( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \).

2. **Understand the Process of Heating Gypsum**:
When gypsum is heated, it undergoes a dehydration reaction. This means that water molecules are removed from the gypsum structure.

3. **Write the Reaction for Heating Gypsum**:
When gypsum is heated at 393 K, the reaction can be represented as:
\[ \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \xrightarrow{393K} \text{CaSO}_4 \cdot \text{H}_2\text{O} + \frac{3}{2} \text{H}_2\text{O} \]
Here, one molecule of water is retained in the product, and \( \frac{3}{2} \) molecules of water are released.

4. **Identify the Product**:
The product formed after heating gypsum at 393 K is \( \text{CaSO}_4 \cdot \text{H}_2\text{O} \) (calcium sulfate hemihydrate), which is also known as plaster of Paris.

5. **Final Answer**:
Therefore, the correct answer to the question is \( \text{CaSO}_4 \cdot \text{H}_2\text{O} \).