Question

To a small amount of copper oxide in a beaker, when we add dilute hydrochloric acid slowly with stirring, the change in the colour of the solution is due to the formation of ______.

विकल्प

• Copper (II) oxide, which is black in colour.

• Copper (I) chloride, which is blue in colour.

• Copper (II) chloride, which is blue-green in colour.

• Copper (I) oxide, which is black in colour.

Answer 1

To a small amount of copper oxide in a beaker, when we add dilute hydrochloric acid slowly with stirring, the change in the colour of the solution is due to the formation of copper (II) chloride, which is blue-green in colour.

Explanation:

When black copper (II) oxide reacts with dilute hydrochloric acid, a neutralisation reaction occurs. The copper oxide dissolves to form copper (II) chloride (CuCl₂) and water, which imparts a characteristic blue-green colour to the resulting solution. 

The chemical equation for this reaction is:

\[\ce{CuO_{(s)} + 2HCl_{(aq)} -> CuCl2_{(aq)} + H2O_{(l)}}\]