Formula of plaster of Paris is

Options

A. `CaSO_(2).2H_(2)O`
B. `2(CaSO_(4).1//2H_(2)O)`
C. `2CaO. H_(2)O`
D. `CaCO_(3)`

Explanation

To determine the formula of plaster of Paris, we need to understand its chemical composition. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the main component
Plaster of Paris is primarily composed of calcium sulfate.

### Step 2: Determine the hydration state
Plaster of Paris is a hemihydrate form of calcium sulfate. This means it contains water in its structure but not in the same proportion as in fully hydrated forms.

### Step 3: Write the chemical formula
The chemical formula for plaster of Paris is:
\[ \text{CaSO}_4 \cdot \frac{1}{2} \text{H}_2\text{O} \]
This indicates that for every molecule of calcium sulfate, there is half a molecule of water associated with it.

### Step 4: Simplify the formula
To express it in a more common format, we can write it as:
\[ \text{CaSO}_4 \cdot 1/2 \text{H}_2\text{O} \]
This can also be represented as:
\[ \text{CaSO}_4 \cdot 1.5 \text{H}_2\text{O} \]
However, the most recognized and accepted formula is:
\[ \text{CaSO}_4 \cdot 1/2 \text{H}_2\text{O} \]

### Step 5: Conclusion
Thus, the formula of plaster of Paris is:
\[ \text{CaSO}_4 \cdot \frac{1}{2} \text{H}_2\text{O} \]