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Answer the following. (Science 2026 31/1/1 Q29a)

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

CBSE Class 10 Science 2026: question 29(a)

Set in the CBSE Class 10 board exam of 2026, paper 31/1/1, section B, question 29(a), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q29(a) · 5 marks · Short answerCarbon and its Compounds

Answer the following.

  1. (i)

    Give reasons for the following: (I) Covalent compounds are poor conductor of electricity. (II) Soap does not form lather in hard water. (III) Carbon shows catenation but silicon does not.

    3 marks
  2. (ii)

    Write chemical equations for the following: (I) Oxidation of ethanol by acidified K2Cr2O7. (II) Hydrogenation of ethene.

    2 marks

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

Hints

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

Hint 1

Electric current needs mobile charged particles.

Hint 2

Compare the strengths of C–C and Si–Si bonds.

Hint 3

Acidified dichromate is an oxidising agent; hydrogenation needs a nickel catalyst.

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)(I) Covalent compounds are formed by sharing of electrons, so they do not form ions (charged particles). With no ions to carry charge, they are poor conductors of electricity.

    1 mark

  2. (i)(II) Hard water contains calcium and magnesium salts. Soap reacts with these salts to form an insoluble precipitate called scum, so the soap is used up and does not form lather easily.

    1 mark

  3. (i)(III) C–C bonds are very strong and stable because carbon is a small atom, so carbon can form long chains (catenation). Si–Si bonds are much weaker, so silicon does not form long stable chains.

    1 mark

  4. (ii)(I) (ethanol is oxidised to ethanoic acid)

    1 mark

  5. (ii)(II) (ethene is hydrogenated to ethane)

    1 mark

Answer: (i) (I) No ions formed; (II) Ca/Mg salts form scum with soap; (III) C–C bonds strong, Si–Si bonds weak; (ii) CH₃CH₂OH → CH₃COOH; CH₂=CH₂ + H₂ → CH₃CH₃ (Ni)

Where the marks are

  • No ions/charged particles in covalent compounds (1 mark)
  • Scum formed with Ca²⁺/Mg²⁺ salts (1 mark)
  • Strong C–C bond versus weak Si–Si bond (1 mark)
  • Oxidation equation (1 mark)
  • Hydrogenation equation with Ni (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 31/1/1: 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.