Question

When crystals of copper sulphate are strongly heated, the residue obtained is _____________.

• A. red in colour
• B. blue in colour
• C. green in colour
• D. colourless

Answer 1

The correct option is D colourless

Copper sulphate crystals are blue in colour due to the presence of water of crystallization. The colour in only there because of the presence of water of crystallization.

When they are heated strongly anhydrous copper sulphate is formed that is white in colour(colorless). This is so because of removal of water of crystallization.

The reaction is given by,

$CuS{O}_4.5H_{2}0\left(blue\right)\to CuS{O}_4\left(white\right)+5H_{2}O$