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State reasons for the… (Class 10 Science 2024, Q27)

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ScienceCBSE Class 10 · Board exam 2024, set 31/3/1 · 3 marks · Short answer

CBSE Class 10 Science 2024: question 27

Set in the CBSE Class 10 board exam of 2024, paper 31/3/1, section C, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerMetals and Non-metals

State reasons for the following :
(a) Zinc oxide is an amphoteric oxide.
(b) Sodium metal is stored in bottle filled with kerosene oil.
(c) In the reactions of nitric acid with metals, generally hydrogen gas is not evolved.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/3/1.

Hints

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

Hint 1

Amphoteric means showing both acidic and basic behaviour.

Hint 2

Why would a very reactive metal be dangerous if left open to air?

Hint 3

What does an oxidising agent do to hydrogen?

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) Zinc oxide reacts with both acids and bases to give salt and water, so it is amphoteric. For example: and .

    1 mark

  2. (b) Sodium is very reactive. In open air it reacts vigorously with oxygen and moisture and may catch fire. Keeping it under kerosene cuts off contact with air and water and prevents accidental fire.

    1 mark

  3. (c) Nitric acid is a strong oxidising agent. It oxidises the hydrogen produced to water, while itself being reduced to oxides of nitrogen. So gas is generally not evolved. (Mg and Mn with very dilute are exceptions.)

    1 mark

Answer: (a) ZnO reacts with both acids and bases to give salt and water. (b) Na reacts vigorously with air/moisture and catches fire; kerosene prevents contact. (c) HNO₃ is a strong oxidising agent and oxidises H₂ to water.

Where the marks are

  • ZnO reacts with acids as well as bases forming salt and water (1 mark)
  • Sodium reacts vigorously with air and catches fire; kerosene prevents contact (1 mark)
  • HNO₃ is a strong oxidising agent that oxidises H₂ to H₂O (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 paper2024 board paper, set 31/3/1: 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.