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Answer the following. (Class 10 Science 2025, Q34B)

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ScienceCBSE Class 10 · Board exam 2025, set 31/5/1 · 5 marks · Long answer

CBSE Class 10 Science 2025: question 34(B)

Set in the CBSE Class 10 board exam of 2025, paper 31/5/1, section D, question 34(B), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q34(B) · 5 marks · Long answerCarbon and its Compounds

Answer the following.

  1. (a)

    Write the molecular formula of ethyne and draw its electron dot structure.

    0 marks
  2. (b)

    Write chemical equation to show the reaction of ethanol with (i) Sodium metal (ii) Ethanoic acid (in the presence of an acid) (iii) Acidified potassium dichromate. Write the name of the product formed in each case.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/5/1.

Hints

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

Hint 1

Ethyne is an alkyne; how many electron pairs must the two carbons share?

Hint 2

Sodium gives off a gas with ethanol; an acidified oxidising agent turns an alcohol into a carboxylic acid.

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) Molecular formula of ethyne: ().

    1 mark

  2. (a) Electron dot structure: the two carbon atoms share three pairs of electrons (a triple bond), and each carbon shares one pair with a hydrogen atom: . Each C then has 8 electrons and each H has 2.

    1 mark

  3. (b)(i) . Products: sodium ethoxide and hydrogen gas.

    1 mark

  4. (b)(ii) . Product: ethyl ethanoate (ester).

    1 mark

  5. (b)(iii) . Product: ethanoic acid (oxidation of ethanol).

    1 mark

Answer: (a) C₂H₂, H:C:::C:H; (b)(i) sodium ethoxide + H₂; (ii) ethyl ethanoate; (iii) ethanoic acid

Where the marks are

  • Molecular formula C₂H₂ (1 mark)
  • Electron dot structure showing triple bond (1 mark)
  • Reaction with Na, sodium ethoxide (1 mark)
  • Esterification, ethyl ethanoate (1 mark)
  • Oxidation to ethanoic acid (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Carbon and its Compounds, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/5/1: 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.