Question

Give a reason for the following:

Pale blue colour is obtained on adding ammonium hydroxide solution to copper sulphate.

Answer 1

Pale blue colour is obtained because ammonium hydroxide reacts with copper sulphate solution to form a pale blue precipitate of copper(II) hydroxide.

\[\ce{CuSO4 ​+ 2NH4​OH → Cu(OH)2​↓ + (NH4​)2​SO4​}\]

Hence, the pale blue colour is due to the formation of copper(II) hydroxide precipitate.