Question

In adding dilute HCl to copper oxide powder, the solution formed is blue-green. Write the balanced equation of the reaction taking place.

Answer 1

Hint: You can try recalling a blue-green solution of a compound which has copper. The reaction taking place between HCl and copper oxide is a kind of displacement reaction. Now try to find the answer.

Complete step by step answer:

When dilute HCl reacts with copper oxide, the reaction is as follows:
$CuO(s)\quad +\quad 2HCl(aq)\quad \rightarrow \quad CuCl_{ 2 }(aq)\quad +\quad H_{ 2 }O(l)$
This is a double displacement reaction. The soluble copper(II)chloride is blue-green in color and is responsible for the color of the solution formed. When dilute HCl is added to a small amount of copper oxide in a beaker, a greenish-yellow gas is released and a bluish-green solution is formed.
Since the metal oxides such as a Copper oxide (CuO) are basic in nature, it reacts with acids such as HCl to form the corresponding salt and water. The reaction that occurs is called a redox reaction.

Therefore, we have written the balanced equation of the reaction taking place between dilute HCl and copper oxide powder.

Note: You should know that $CuCl_{ 2 }$ is a light brown solid, which slowly absorbs moisture to form a blue-green dihydrate. Both the anhydrous and the dihydrate forms occur naturally as the very rare minerals tolbachite and eriochalcite, respectively.
CuO is a black solid, it is one of the two stable oxides of copper, the other being $Cu_{ 2 }O$ or cuprous oxide.