The composition formula of
i) Gypsum :
ii) plaster of paris :
iii) Glauber's Salt:

Answer

To find the composition formulas for the given compounds, we can follow these steps:

### Step 1: Identify the composition formula of Gypsum
- Gypsum is a mineral composed of calcium sulfate dihydrate. Its chemical formula is:
\[ \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \]

### Step 2: Identify the composition formula of Plaster of Paris
- Plaster of Paris is made from gypsum that has been heated to remove water. Its chemical formula is:
\[ \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \quad \text{(or more commonly written as } \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \text{ in some contexts)} \]
However, the more accurate representation is:
\[ \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \]

### Step 3: Identify the composition formula of Glauber's Salt
- Glauber's Salt is sodium sulfate decahydrate. Its chemical formula is:
\[ \text{Na}_2\text{SO}_4 \cdot 10\text{H}_2\text{O} \]

### Summary of Composition Formulas
- Gypsum: \(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\)
- Plaster of Paris: \(\text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O}\) (or \(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\) in some contexts)
- Glauber's Salt: \(\text{Na}_2\text{SO}_4 \cdot 10\text{H}_2\text{O}\)