Question

Presence of water can be detected by:

• A. adding a drop to anhydrous copper suphate which changes its colour from white to blue
• B. by boiling and testing for the presence of $H_2$ and $O_2$
• C. by seeing its colour and transparency
• D. by checking the production of lather when mixed with soap

Answer 1

The correct option is A adding a drop to anhydrous copper suphate which changes its colour from white to blue

Anhydrous $CuS{O}_4$ is white which on reaction with $H_{2}O$ forms hydrated $CuS{O}_4$ which is blue in colour.

$\underset{\text{White colour}}{CuS{O}_4}+5H_{2}O\to \underset{\text{Blue colour}}{CuS{O}_4.5H_{2}O}$