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Science (086) — AI-generated practice question

AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.

Q1. [1] straightforward exam-ready
When iron nails are placed in copper sulphate solution, the blue colour of the solution gradually fades. Which of the following correctly explains this observation? (A) Iron dissolves in copper sulphate to form a blue precipitate (B) Copper is displaced by iron, and iron sulphate solution is formed (C) Copper sulphate undergoes photochemical decomposition (D) A double displacement reaction produces iron oxide
  1. A Iron dissolves in copper sulphate to form a blue precipitate
  2. B Iron displaces copper from copper sulphate, forming iron sulphate
  3. C Copper sulphate undergoes thermal decomposition
  4. D A double displacement reaction forms iron oxide
Generated by claude-sonnet-4-6 · 2026-06-26 00:53 · grounding rag
Model Answer

(B) Iron displaces copper from copper sulphate, forming iron sulphate: $\text{Fe}(s) + \text{CuSO}_4(aq) \rightarrow \text{FeSO}_4(aq) + \text{Cu}(s)$. Since FeSO₄ is pale green, the blue colour fades.

Source: Chapter 1, Section 1.2.3 Displacement Reaction

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Explanation

This is a displacement reaction — iron (more reactive) displaces copper from CuSO₄. The blue colour is due to Cu²⁺ ions; as they are replaced by Fe²⁺ (iron sulphate, which is light green/colourless), the blue fades. Options C and D are wrong reaction types; Option A is incorrect because no blue precipitate forms.

Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.