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: Defining Water of Crystallisation:
Water of crystallisation denotes water molecules chemically bonded within a compound's crystal structure, forming an essential part of its crystalline state.

Step 2: Examining Provided Compounds:
- FeSO₄ (Iron(II) sulfate) can exist as hydrated FeSO₄·7H₂O, indicating 7 molecules of crystallisation water per molecule of compound.
- CuSO₄ (Copper(II) sulfate) commonly forms CuSO₄·5H₂O, containing 5 molecules of crystallisation water.
- CaSO₄ (Calcium sulfate) typically forms CaSO₄·2H₂O, with 2 molecules of crystallisation water.
- Na₂CO₃ (Sodium carbonate) forms Na₂CO₃·10H₂O, containing 10 molecules of crystallisation water.

Step 3: Determination:
Of the compounds listed, FeSO₄ forms a crystalline structure with 7 molecules of water of crystallisation per molecule of compound, the highest quantity among the given substances. Consequently, FeSO₄ is the correct identification.