AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
The solution turns blue-green in colour, due to the formation of copper(II) chloride (CuCl₂).
Source: Chapter 2, Section 2.1.5 – Reaction of Metallic Oxides with Acids
The textbook explicitly states in Activity 2.7 that "the colour of the solution becomes blue-green" when copper oxide dissolves in dilute HCl, forming copper(II) chloride. Examiners expect the exact colour "blue-green" and may also award marks for naming the product formed.