- Take a small amount of copper oxide in a beaker and add dilute hydrochloric acid slowly while stirring.
- Note the colour of the solution. What has happened to the copper oxide?
✅ Answer: The solution becomes blue-green colour and the copper oxide dissolves. The colour is due to the formation of copper(II) chloride (CuCl2).
CuO + 2HCl → CuCl2 + H2O