Question

What happens when crystals of Blue vitriol are added to the beaker containing concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$? Explain the observation.

Answer 1

Part 1: Dehydrating agent

• Dehydrating agents: The substance that can even remove chemically combined water from the compound is called a dehydrating agent.
• Some of the well-known dehydrating agents are concentrated Sulfuric acid, concentrated Phosphoric acid and hot Aluminium oxide, etc.

Part 2: Reaction of blue vitriol with concentrated Sulphuric acid

• Now when crystals of Blue vitriol(Copper sulphate pentahydrate) are treated with concentrated Sulphuric acid, the water of crystallization is removed from it.

$\underset{(\mathrm{Copper}\mathrm{Sulphate}\mathrm{pentahydrate})}{{\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}\stackrel{(\mathrm{conc}.){\mathrm{H}}_2{\mathrm{SO}}_4}{\to }\underset{(\mathrm{Copper}\mathrm{sulphate})}{{\mathrm{CuSO}}_4\left(\mathrm{s}\right)}+\underset{\left(\mathrm{water}\right)}{\underbrace{5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}}$.

• The blue colour of the crystal fades away and white color powder is obtained.