Q1. [2] § 1.1.1 Writing a Chemical Equation § 1.1.2 Balanced Chemical Equations § 1.2.5 Oxidation and Reduction
(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.
Previously asked in CBSE board exam
2023 31/4/1 Q21 (A)
Generated by claude-sonnet-4-6 · 2026-06-14 10:29 · grounding rag
Model Answer
(i) The compound formed is copper(II) chloride. Its colour is blue-green.
(ii) Balanced chemical equation:
$$\text{CuO}(s) + 2\text{HCl}(aq) \rightarrow \text{CuCl}_2(aq) + \text{H}_2\text{O}(l)$$
Source: Chapter 2, Section 2.1.5 (Reaction of Metallic Oxides with Acids)
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Explanation
- The passage (Activity 2.7) explicitly states the solution turns blue-green due to formation of copper(II) chloride — use the exact name and colour.
- The balanced equation follows the general pattern: Metal oxide + Acid → Salt + Water. Ensure coefficient 2 before HCl to balance the equation — this is a commonly tested balancing point.
- State symbols (s), (aq), (l) add marks if included.
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