Question

Give two tests for identification of water vapour.

Answer 1

Two tests for the identification of water vapours are as follows:

1. In the presence of water vapours, the anhydrous white Copper sulphate (CuSO₄) powder turns into blue crystals of Copper sulphate pentahydrate (CuSO4.5H₂O).

$$\begin{gathered} {\mathrm{CuSO}}_4\left(\mathrm{s}\right)\stackrel{\mathrm{water}\mathrm{vapours}}{\to }{\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right) \\ (\mathrm{Copper}\mathrm{sulphate})(\mathrm{Copper}\mathrm{sulphate}) \\ \left(\mathrm{anhydrous}\right)\left(\mathrm{hydrated}\right) \end{gathered}$$

2. In the presence of water vapours, the blue Cobalt chloride (CoCl₂) powder turns pink due to the formation of hydrated salt Cobalt chloride hexahydrate (CoCl₂.6H₂O).

When dry Cobalt chloride (blue) comes in contact with water vapours, it turns pink indicating the presence of water vapours.