Solution:
concept - The compound that is formed when HCL is added to powder of copper oxide is copper (II) chloride. In the double displacement type of reaction, the two ionic compounds react and their ions interchange to form a new set of ionic compounds.When dilute reacts with copper oxide, the reaction is as follows:
The soluble copper (II)chloride or cupric chloride is blue-green in colour and is responsible for the colour of the solution formed.
Hence, when dilute HCl is added to a small amount of copper oxide in a beaker, a bluish-green solution is formed. The new compound formed is Copper (II) Chloride.
Hence, the answer is Copper (II) Chloride or cuprous chloride.