Question

What would be the color of the solution when dilute HCl is added to copper(II) oxide?

Answer 1

Solution:

When dilute hydrochloric acid (HCl) is added to copper(II) oxide (CuO):

$\mathrm{HCl}\left(\mathrm{aq}\right)+\mathrm{CuO}\left(\mathrm{s}\right)\to {\mathrm{CuCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)$,

the formation of copper chloride (${\mathrm{CuCl}}_2$) leads to the solution acquiring bluish-green color.

Hence, the solution will acquire a bluish-green color due to ${\mathrm{CuCl}}_2$.