Question

On heating the blue solid, hydrated copper(II) sulphate, ................. is given off :

• A. $N{O}_2$
• B. Steam
• C. $HCl$
• D. Oxygen

Answer 1

The correct option is B Steam

On heating the blue solid, hydrated copper(II) sulphate, steam is given off and the white solid of anhydrous copper(II) sulphate is formed. When the white solid is cooled and water added, blue hydrated copper(II) sulphate is reformed i.e. a reversible reaction.

$CuS{O}_4.5H_{2}O\left(s\right)\to CuS{O}_4\left(s\right)+5H_{2}O\left(g\right)$

The dehydration decomposition to give the white solid is the forward reaction and the 're-hydration' to reform the blue crystals is the backward reaction.