Skip to content

Alcohol forms a homologous… (Class 10 Science 2026, Q28)

questionbuddy.in/q/cbse-10-science-2026-31-5-1-q28-alcohol-forms-homologous-series-general

ScienceCBSE Class 10 · Board exam 2026, set 31/5/1 · 4 marks · Long answer

CBSE Class 10 Science 2026: question 28

Set in the CBSE Class 10 board exam of 2026, paper 31/5/1, section B, question 28, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q28 · 4 marks · Long answerCompetency-basedCarbon and its Compounds

Alcohol forms a homologous series with general formula –OH and –OH group as functional group. Ethanol is commonly called alcohol and is used in alcoholic drinks. It is good solvent, used in medicines, cough syrups, tonics etc.

  1. (a)

    Write structural formula and name of 4th member of alcohol homologous series.

    1 mark
  2. (b)

    What happens when ethanol is heated with alkaline ? Write chemical equation involved.

    1 mark
  3. (c)

    Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated . Write the name of this reaction.

    2 marks

  4. OR

    (c) OR

    What happens when ethanol is heated with excess concentrated sulphuric acid at 443 K ? Write chemical equation involved. What is the role of concentrated sulphuric acid in this reaction ?

    2 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/5/1.

Hints

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

Hint 1

Put n = 4 in CₙH₂ₙ₊₁OH for part (a).

Hint 2

Alkaline KMnO₄ adds oxygen; an acid + alcohol gives a sweet-smelling compound.

Hint 3

At 443 K hot concentrated H₂SO₄ takes away a water molecule from ethanol.

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) Fourth member (n = 4): (draw all C–H bonds with –OH on the end carbon).

    ½ mark

  2. Name: Butanol ().

    ½ mark

  3. (b) Ethanol is oxidised to ethanoic acid by alkaline KMnO₄ (oxidising agent).

    ½ mark

  4. ½ mark

  5. (c) (ethyl ethanoate, sweet-smelling ester)

    1 mark

  6. This reaction is called esterification.

    1 mark

  7. (c) OR – Ethanol is dehydrated to ethene.

    ½ mark

  8. ½ mark

  9. Role of conc. H₂SO₄: dehydrating agent – it removes water from ethanol.

    1 mark

Answer: (a) CH₃CH₂CH₂CH₂OH, butanol; (b) ethanoic acid formed; (c) CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O, esterification. OR: ethene formed, conc. H₂SO₄ is dehydrating agent.

Where the marks are

  • Structural formula of 4th member (½ mark)
  • Name butanol (½ mark)
  • States oxidation to ethanoic acid (½ mark)
  • Equation with alkaline KMnO₄ (½ mark)
  • Esterification equation (1 mark)
  • Names esterification (1 mark)
  • OR: ethene formed (½ mark), equation at 443 K (½ mark), dehydrating agent (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 paper2026 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.