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A light green coloured… (Class 10 Science 2025, Q21)

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ScienceCBSE Class 10 · Board exam 2025, set 31/6/1 · 2 marks · Very short answer

CBSE Class 10 Science 2025: question 21

Set in the CBSE Class 10 board exam of 2025, paper 31/6/1, section B, question 21, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21 · 2 marks · Very short answerMetals and Non-metals

A light green coloured solution of sulphate salt of metal 'P' is taken in a beaker, a rod of another metal 'Q' is put in this solution as shown the following figures :

Identify the metals 'P' and 'Q' and write its chemical equation for the reaction that occurs. State the conclusion of this reaction in terms of reactivity series of metals.

Figure in the paper: Two beakers with a rod labelled Q dipping into the solution. Left beaker: solution labelled PSO4 (Light Green Solution). An arrow labelled 'After about 1 hour' points to the right beaker: solution labelled QSO4 (Colourless Solution), with rod Q still in the solution. See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/6/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Which common metal sulphate solution is light green in colour?

Hint 2

The colour disappears, so the metal ion in solution has been replaced by the ion of a metal whose sulphate is colourless.

Hint 3

Only a metal placed higher in the reactivity series can push another metal out of its salt solution.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. A light green solution of a sulphate is iron(II) sulphate, so metal P = Iron (Fe).

    ½ mark

  2. The solution turns colourless, so a colourless sulphate forms. Metal Q = Zinc (Zn) (magnesium is also acceptable).

    ½ mark

  3. Reaction: . This is a displacement reaction.

    ½ mark

  4. Conclusion: a more reactive metal displaces a less reactive metal from its salt solution. Zinc is above iron in the reactivity series, so it is more reactive than iron.

    ½ mark

Answer: P = Fe, Q = Zn; ; Zn is more reactive than Fe, so it displaces Fe.

Where the marks are

  • Identifies P as iron (½ mark)
  • Identifies Q as zinc or magnesium (½ mark)
  • Writes the correct displacement equation (½ mark)
  • States that the more reactive metal displaces the less reactive one, i.e. Zn is above Fe (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Metals and Non-metals, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/6/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.