Question

How can you identify the presence of water vapours?

Answer 1

The presence of water vapour can be identified using two standard chemical tests:

1. Anhydrous Copper Sulphate Test:

When water vapour comes into contact with white anhydrous copper sulphate, it turns blue due to the formation of hydrated copper sulphate.

\[ \text{CuSO}_4\text{ (white)} + 5\text{H}_2\text{O} \longrightarrow \text{CuSO}_4 \cdot 5\text{H}_2\text{O}\text{ (blue)} \]

2. Cobalt Chloride Paper Test:

Dry, blue cobalt chloride paper turns pink when exposed to moisture or water vapour.

\[ \text{CoCl}_2\text{ (blue)} + 6\text{H}_2\text{O} \longrightarrow \text{CoCl}_2 \cdot 6\text{H}_2\text{O}\text{ (pink)} \]