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Anirudh took two… (Class 10 Science SQP 2024-25, Q27A)

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ScienceCBSE Class 10 · Sample paper, session 2024-25 · 3 marks · Short answer

CBSE Class 10 Science sample paper 2024-25: question 27(A)

From the official CBSE sample question paper for 2024-25, section C, question 27(A), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27(A) · 3 marks · Short answerCompetency-basedMetals and Non-metals

Anirudh took two metal oxides; aluminium oxide and magnesium oxide as shown in the pictures given below. But he forgot to label them. How will you guide/ help Anirudh to identify the oxides and label them?

Figure in the paper: Two photographs of white powders in petri dishes. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

Think about how each oxide behaves with water.

Hint 2

One of these oxides is basic and the other is amphoteric.

Hint 3

Which oxide would react with sodium hydroxide?

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. Shake a little of each powder with water and test the liquid with red and blue litmus. Magnesium oxide dissolves slightly to form magnesium hydroxide, which is basic and turns red litmus blue:

    1 mark

  2. Aluminium oxide is insoluble in water, so its liquid causes no change in either red or blue litmus.

    1 mark

  3. Confirm with dilute NaOH. Aluminium oxide is amphoteric and dissolves: . Magnesium oxide is basic and does not react with the alkali. Label the powder that turned red litmus blue (and did not dissolve in NaOH) MgO, and the other Al₂O₃.

    1 mark

Answer: MgO solution turns red litmus blue; Al₂O₃ is insoluble (no litmus change) and, being amphoteric, dissolves in NaOH while MgO does not.

Where the marks are

  • MgO with water gives a basic solution that turns red litmus blue (1 mark)
  • Al₂O₃ is insoluble in water, so no litmus change (1 mark)
  • Amphoteric Al₂O₃ reacts with NaOH (and acid), whereas MgO reacts only with acid; labels correctly (1 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 paperSample paper 2024-25: 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.