Question

The blue coloured copper sulphate crystals turn white when treated with sulphuric acid. This is due to the nature of the acid.

• A. dehydrating
• B. oxidising
• C. reducing
• D. colour changing

Answer 1

The correct option is A dehydrating

Sulphuric acid is a dehydrating agent. Copper sulphate crystals are blue in colour. This blue colour is due to the presence of water of crystallisation. When sulphuric acid is added to this, it removes the water of crystallisation making it anhydrous. This changes the colour from blue to white.
${\mathrm{CuSO}}_4.5H_{2}O\left(s\right)+\mathrm{Conc}.H_2{\mathrm{SO}}_4\to {\mathrm{CuSO}}_4\left(s\right)+5H_{2}O\left(g\right)$