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(i) Write the name and… (Class 10 Science 2024, Q34B)

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ScienceCBSE Class 10 · Board exam 2024, set 31/1/1 · 5 marks · Long answer

CBSE Class 10 Science 2024: question 34(B)

Set in the CBSE Class 10 board exam of 2024, paper 31/1/1, 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

(i) Write the name and structure of an organic compound 'X' having two carbon atoms in its molecule and its name is suffixed with '-ol'.
(ii) What happens when 'X' is heated with excess concentrated sulphuric acid at 443 K? Write chemical equation for the reaction stating the conditions for the reaction. Also state the role played by concentrated sulphuric acid in the reaction.
(iii) Name and draw the electron dot structure of hydrocarbon produced in the above reaction.

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

Hints

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

Hint 1

A two-carbon compound ending in '-ol' is an alcohol.

Hint 2

Hot concentrated sulphuric acid removes water from the alcohol. What unsaturated hydrocarbon is left?

Hint 3

In ethene, the carbons share two pairs of electrons with each other.

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) X is ethanol, .

    ½ mark

  2. Structure: , i.e. .

    ½ mark

  3. (ii) Ethanol is dehydrated to ethene.

    ½ mark

  4. 1 mark

  5. Role of concentrated : it acts as a dehydrating agent and removes water from ethanol.

    1 mark

  6. (iii) Hydrocarbon formed: ethene, .

    ½ mark

  7. Electron dot structure: the two C atoms share two electron pairs (a double bond, written ). Each C also shares one electron pair with each of two H atoms. In summary: , with every C having an octet.

    1 mark

Answer: (i) Ethanol, CH₃CH₂OH; (ii) ethene forms: C₂H₅OH → (conc. H₂SO₄, 443 K) C₂H₄ + H₂O, with H₂SO₄ as dehydrating agent; (iii) ethene, H₂C::CH₂ electron dot structure

Where the marks are

  • Names ethanol (½ mark) and gives its structure (½ mark)
  • States ethene is formed (½ mark)
  • Equation with conditions conc. H₂SO₄ and 443 K (1 mark; ½ deducted if conditions missing)
  • Conc. H₂SO₄ acts as dehydrating agent (1 mark)
  • Names ethene (½ mark) and draws correct electron dot structure (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 paper2024 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.