The difference of number of water molecules in gypsum and plaster of Pairs is

Options

A. `(5)/(2)`
B. `2`
C. `(1)/(2)`
D. `1(1)/(2)`

Answer

To find the difference in the number of water molecules between gypsum and plaster of Paris, we can follow these steps:

### Step 1: Identify the formulas
- The formula for gypsum is **CaSO₄·2H₂O**.
- The formula for plaster of Paris (POP) is **CaSO₄·(1/2)H₂O**.

### Step 2: Determine the number of water molecules in each compound
- In gypsum, the number of water molecules is **2** (from the formula CaSO₄·2H₂O).
- In plaster of Paris, the number of water molecules is **1/2** (from the formula CaSO₄·(1/2)H₂O).

### Step 3: Calculate the difference in the number of water molecules
To find the difference, we subtract the number of water molecules in plaster of Paris from the number of water molecules in gypsum:

\[ \text{Difference} = \text{Number of water molecules in gypsum} - \text{Number of water molecules in plaster of Paris} \]

\[ \text{Difference} = 2 - \frac{1}{2} \]

### Step 4: Simplify the calculation
To perform the subtraction, we can convert 2 into a fraction:

\[ 2 = \frac{4}{2} \]

Now, we can subtract:

\[ \text{Difference} = \frac{4}{2} - \frac{1}{2} = \frac{4 - 1}{2} = \frac{3}{2} \]

### Conclusion
The difference in the number of water molecules between gypsum and plaster of Paris is **3/2**.

### Final Answer
The correct option is **D: 3/2**.

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