Gypsum ion heating at `120-130^(@)C` gives:

Options

A. anhydrous salt
B. hemihydrate
C. monohydrate
D. dihydrate

Explanation

To solve the question regarding the heating of gypsum at `120-130°C`, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chemical Composition of Gypsum**:
- Gypsum is chemically known as calcium sulfate dihydrate, with the formula \( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \).

2. **Understand the Heating Process**:
- When gypsum is heated, it undergoes a dehydration process where water molecules are removed.

3. **Determine the Temperature Range**:
- The question specifies heating gypsum at a temperature of `120-130°C`. This range is crucial as it indicates the extent of dehydration.

4. **Identify the Product of Heating**:
- At `120-130°C`, gypsum loses one of its water molecules, resulting in the formation of calcium sulfate hemihydrate, which has the formula \( \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \).

5. **Conclusion**:
- Therefore, when gypsum is heated at `120-130°C`, the product formed is calcium sulfate hemihydrate.

### Final Answer:
When gypsum is heated at `120-130°C`, it gives calcium sulfate hemihydrate, represented as \( \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \).

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