Question

The blue-green colour of the solution is due to the formation of copper(II) chloride in the reaction' this is an example of which kind of chemical reaction?

Answer 1

The blue-green colour solution of copper(II) chloride:

• Copper(II) chloride$\left({\mathrm{CuCl}}_2\right)$ gets formed when copper oxide $\left(\mathrm{CuO}\right)$ undergoes a reaction with hydrochloric acid$\left(\mathrm{HCl}\right)$.
• The balanced chemical reaction for this is given as follows:

$\underset{\left(\mathrm{Copper}\mathrm{oxide}\right)}{\mathrm{CuO}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Hydrochloric}\mathrm{acid}\right)}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\left(\mathrm{Copper}\left(\mathrm{II}\right)\mathrm{chloride}\right)}{{\mathrm{CuCl}}_2\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• Copper(II) chloride$\left({\mathrm{CuCl}}_2\right)$ is light brown colour solid but, after adsorption of moisture formed during the reaction its colour changes into blue-green.

Hence, the blue-green colour of the solution which is due to the formation of copper(II) chloride in the reaction' is an example of the reaction of metallic oxide with acid.