Question

Consider the following compounds:
FeSO₄ ; CuSO₄ ; CaSO₄ ; Na₂CO₃
The compound having the maximum number of water of crystallisation in its crystalline form in one molecule is:

• A. FeSO₄
• B. CuSO₄
• C. CaSO₄
• D. Na₂CO₃

Answer 1

The Correct Option is A

Step 1: Understanding water of crystallisation:
Water of crystallisation refers to the water molecules that are chemically bound within the crystalline structure of a compound. These water molecules are an integral part of the crystalline form of the substance.

Step 2: Analyzing the given compounds:
- FeSO₄ (Iron(II) sulfate) can form hydrated compounds like FeSO₄·7H₂O, meaning it contains 7 molecules of water of crystallisation in one molecule.
- CuSO₄ (Copper(II) sulfate) commonly forms CuSO₄·5H₂O, which contains 5 molecules of water of crystallisation.
- CaSO₄ (Calcium sulfate) typically forms CaSO₄·2H₂O, containing 2 molecules of water of crystallisation.
- Na₂CO₃ (Sodium carbonate) forms Na₂CO₃·10H₂O, containing 10 molecules of water of crystallisation.

Step 3: Conclusion:
Among the given compounds, FeSO₄ forms a crystalline compound with 7 molecules of water of crystallisation in one molecule, which is the highest among the listed compounds. Therefore, the correct answer is FeSO₄.