Question

What would you observe in the following case:

Concentrated Sulphuric acid is added dropwise to the crystals of hydrated Copper Sulphate.

Answer 1

Dehydration of hydrated copper sulphate:

• When concentrated Sulphuric acid ( ${\mathrm{H}}_2{\mathrm{SO}}_4$) is added dropwise to the crystals of hydrated Copper sulphate $\left({\mathrm{CuSO}}_{4·}5{\mathrm{H}}_2\mathrm{O}\right)$, it changes the colour of hydrated copper Sulphate from blue to white.
• ${\mathrm{H}}_2{\mathrm{SO}}_4$ acts as a dehydrated agent, it removes the water molecule from the compound and forms the anhydrous Copper sulphate which has white colour.

Balanced chemical equation:

$\underset{\mathrm{Hydrated}\mathrm{Copper}\mathrm{sulphate}}{{\mathrm{CuSO}}_4·5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)}\stackrel{\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }\underset{\mathrm{Anhydrous}\mathrm{Copper}\mathrm{sulphate}}{{\mathrm{CuSO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

Hence, a change in the color of hydrated Copper sulphate from blue to white is observed.