A' is an important constituent of cement which i responsible for setting of cement. What is the number of water of crystallisation present in 'A'?

Options

A. 2
B. 1
C. 1
D. 44198

Answer

To solve the question regarding the number of water of crystallization present in 'A', which is an important constituent of cement responsible for its setting, we can follow these steps:

### Step-by-Step Solution:

1. **Identify 'A':**
- The question mentions that 'A' is an important constituent of cement responsible for its setting. This constituent is known to be gypsum.

2. **Chemical Composition of Gypsum:**
- Gypsum is chemically known as calcium sulfate dihydrate. Its chemical formula is CaSO₄·2H₂O.

3. **Understanding Water of Crystallization:**
- The term "water of crystallization" refers to the water molecules that are integrated into the crystal structure of a compound. In the case of gypsum, the "dihydrate" indicates that there are two water molecules associated with each formula unit of calcium sulfate.

4. **Count the Water Molecules:**
- From the formula CaSO₄·2H₂O, we can see that there are 2 water molecules (2H₂O) associated with each molecule of gypsum.

5. **Conclusion:**
- Therefore, the number of water of crystallization present in 'A' (gypsum) is 2.

### Final Answer:
The number of water of crystallization present in 'A' (gypsum) is **2**.

---