Option 1 states that iron sulphate and copper sulphate crystals have the same number of water of crystallization. This statement is incorrect. Iron sulphate crystals have six water of crystallization molecules, while copper sulphate crystals have five water of crystallization molecules. Therefore, these two compounds do not have the same number of water of crystallization.

Option 2 states that iron sulphate and zinc sulphate crystals have the same number of water of crystallization. This statement is correct. Both iron sulphate and zinc sulphate crystals have seven water of crystallization molecules each. Therefore, these two compounds have the same number of water of crystallization.

Option 3 states that zinc sulphate and copper sulphate crystals have the same number of water of crystallization. This statement is incorrect. As mentioned earlier, zinc sulphate crystals have seven water of crystallization molecules, while copper sulphate crystals have five water of crystallization molecules. Therefore, these two compounds do not have the same number of water of crystallization.

Option 4 states that iron sulphate, copper sulphate, and zinc sulphate crystals each have the same number of water of crystallization. This statement is incorrect. As already discussed, iron sulphate has six water of crystallization molecules, copper sulph