Question

Which of the following salts does not contain water of crystallisation?

Answer 1

The water of crystallisation denotes the number of water molecules present in the crystal structure of salts.

The table given below is showing the chemical formula of the given chemical compounds.
$$\begin{array}{ccc}\text{Chemical compound}& \text{Formula}& \text{No. of water molecules}\\ \text{Common salt}& \text{NaCl}& \text{0}\\ \text{Blue vitriol}& {\text{CuSO}}_4.5{\text{H}}_2\text{O}& \text{5}\\ \text{Green vitriol}& \text{Fe}{\text{SO}}_4.7{\text{H}}_2\text{O}& \text{7}\\ \text{Gypsum}& {\text{CaSO}}_4.2{\text{H}}_2\text{O}& \text{2}\end{array}$$
So from the table, it is clear that only common salt does not contain water of crystallisation.