Section B: Give a very short answer to the question given below.
 
21.a. A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution. 
 
i. Write the name of the compound formed and its colour.
ii. Write a balanced chemical equation for the reaction involved.
 
i. Name of the compound formed and its colour:  The compound formed is copper(II) chloride (CuCl₂), which is typically in colour when in solution.
 
ii. Balanced chemical equation: The balanced chemical equation for the reaction between copper oxide and hydrochloric acid is:

In this reaction Copper oxide (CuO), a black solid, reacts with hydrochloric acid (HCl), a colorless liquid. The products are copper(II) chloride (CuCl₂), which is a blue-green solution, and water (H₂O), a colorless liquid.