Q1. [2]
One student was comparing the reactivity of different metals for his science project. He added iron filings in four test tubes A, B, C and D containing aqueous solutions of ZnSO₄, CuSO₄, FeSO₄ and Al₂(SO₄)₃.
Read the following passage and answer the questions that follow :
- (i) In which of the test tubes will he observe the reaction to be the most vigorous and why ? [1]
- (ii) Write a balanced equation for the reaction involved. [1]
Previously asked in CBSE board exam
2026 31/2/1 Q25
Generated by claude-sonnet-4-6 · 2026-06-15 06:46 · grounding stimulus
Model Answer
(i) Test tube B (containing CuSO₄) will show the most vigorous reaction, because iron is more reactive than copper and can displace it from its salt solution. The difference in reactivity between Fe and Cu is the greatest among the four options.
(ii) Balanced equation:
$$\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}$$
---
Explanation
- Iron cannot displace Zn or Al (both more reactive than Fe), and FeSO₄ already contains Fe, so no reaction occurs in A, C, D.
- Examiners expect you to justify the choice using the reactivity series — just naming the test tube without reason loses the mark.
- The balanced equation must show correct formulae and be properly balanced; state symbols are a bonus but not mandatory for full marks here.
If a question refers to an image, map, graph or diagram that is not shown here, open the Study Guide single page app, go to
Library and find the actual CBSE question paper. The original papers are also available on the CBSE website:
cbse.gov.in.