CBSE10 Questions & Answers

Q001

Year 2026 Set SET1 18. 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 : N (A) Copper(II) oxide, which is black in colour. (B) (C) Copper(I) chloride, which is blue in colour. Copper(I) chloride, which is blue-green in colour. (D) Copper(I) oxide, which is black in colour.

Problem

When a small amount of copper oxide is added to a beaker containing dilute hydrochloric acid, the change in the color of the solution is due to the formation of:

Solution

Step 1: The reaction between copper oxide (CuO) and hydrochloric acid (HCl) can be represented by the following balanced chemical equation:

$$ CuO + 2 HCl \rightarrow CuCl + H_2O $$

Step 2: In this reaction, copper oxide reacts with hydrochloric acid to form copper chloride (CuCl) and water (H₂O).

Final Answer: The change in the color of the solution is due to the formation of copper(I) chloride (CuCl), which is blue in color.