Plaster of Paries is obtained

Options

A. by adding water to calcium sulphate
B. by adding sulphuric acid to calcium hydroxide
C. by heating gypsum to a very high temperature
D. by heating gypsum to `100^(@)C` .

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks how Plaster of Paris is obtained. Plaster of Paris is a material used in construction and art, and it is derived from gypsum.

2. **Identifying Gypsum**: Gypsum is a mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.

3. **Heating Gypsum**: To obtain Plaster of Paris, gypsum must be heated. The heating process involves removing water from the gypsum. Specifically, gypsum is heated to about 100 degrees Celsius.

4. **Chemical Reaction**: The chemical reaction that occurs when gypsum is heated is:
\[ \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \xrightarrow{\text{heat}} \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} + \frac{3}{2}\text{H}_2\text{O} \]
This reaction shows that when gypsum is heated, it loses water and forms Plaster of Paris, which is calcium sulfate hemihydrate (CaSO4·0.5H2O).

5. **Conclusion**: Therefore, Plaster of Paris is obtained by heating gypsum at 100 degrees Celsius.

**Final Answer**: Plaster of Paris is obtained by heating gypsum (CaSO4·2H2O) at 100 degrees Celsius.

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