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1 gram of solid sodium… (Class 10 Science 2024, Q21a)

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ScienceCBSE Class 10 · Board exam 2024, set 31/4/1 · 2 marks · Very short answer

CBSE Class 10 Science 2024: question 21(a)

Set in the CBSE Class 10 board exam of 2024, paper 31/4/1, section B, question 21(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(a) · 2 marks · Very short answerAcids, Bases and Salts

1 gram of solid sodium chloride was taken in a clean and dry test tube and concentrated sulphuric acid was added to it.
(i) Name the gas evolved in the reaction.
(ii) What will be observed when this gas is tested with (I) dry, and (II) wet blue litmus paper ? Write your conclusion about the nature (acidic/basic) of this gas.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/4/1.

Hints

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

Hint 1

Think about which part of NaCl combines with H⁺ from the acid to form a gas.

Hint 2

Acids show their acidic property only when they can produce H⁺ ions, and that needs water.

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. (i) Concentrated sulphuric acid reacts with sodium chloride to give hydrogen chloride (HCl) gas: .

    ½ mark

  2. (ii)(I) With dry blue litmus paper there is no change in colour, because dry HCl gas does not release ions.

    ½ mark

  3. (ii)(II) Wet blue litmus paper turns red, because HCl dissolves in the water on the paper and forms ions.

    ½ mark

  4. Conclusion: HCl gas is acidic in nature. It shows its acidic behaviour only in the presence of water.

    ½ mark

Answer: (i) Hydrogen chloride (HCl) gas; (ii) (I) dry blue litmus shows no change, (II) wet blue litmus turns red; the gas is acidic.

Where the marks are

  • Names HCl gas (½ mark)
  • Dry blue litmus shows no colour change (½ mark)
  • Wet blue litmus turns red (½ mark)
  • Concludes that the gas is acidic (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Acids, Bases and Salts, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/4/1: 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.