Answer the following. (i) Name a commercially important carbon compound having functional group -OH and write its molecular formula. (ii) Write chemical equation to show its reaction with (1) Sodium metal (2) Excess conc. sulphuric acid (3) Ethanoic acid in the presence of an acid catalyst (4) Acidified potassium dichromate. Also write the name of the product formed in each case.

ScienceCBSE Class 10 · Board exam 2024, set 31/2/1 · 5 marks · Long answer

CBSE Class 10 Science 2024: question 34(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/2/1, 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.

(i)
Name a commercially important carbon compound having functional group $- OH$ and write its molecular formula.
0 marks
(ii)
Write chemical equation to show its reaction with (1) Sodium metal (2) Excess conc. sulphuric acid (3) Ethanoic acid in the presence of an acid catalyst (4) Acidified potassium dichromate. Also 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 2024 board paper, set 31/2/1.

Hints

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

Hint 1

Think of the alcohol found in beverages and used as a common solvent.

Hint 2

For each reagent, decide what it does: Na displaces H, conc. H₂SO₄ removes water, a carboxylic acid forms an ester, and K₂Cr₂O₇ oxidises.

Hint 3

Ethanol gives sodium ethoxide, ethene, an ester and ethanoic acid in turn. Balance each equation.

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.

(i) A commercially important carbon compound with the $- OH$ (alcohol) functional group is ethanol (ethyl alcohol).
½ mark
(i) Molecular formula of ethanol: $C_{2} H_{5} OH$ .
½ mark
(ii)(1) Reaction with sodium metal. Hydrogen gas is evolved: $2 C_{2} H_{5} OH + 2Na \to 2 C_{2} H_{5} ONa + H_{2} ↑$
½ mark
Product: sodium ethoxide ( $C_{2} H_{5} ONa$ ), along with hydrogen gas.
½ mark
(ii)(2) Heating with excess concentrated sulphuric acid at 443 K. The acid acts as a dehydrating agent and removes water: $C_{2} H_{5} OH Excess conc. H_{2} S O_{4} 443 K C H_{2} = C H_{2} + H_{2} O$
½ mark
Product: ethene ( $C H_{2} = C H_{2}$ ).
½ mark
(ii)(3) Reaction with ethanoic acid in the presence of an acid catalyst (esterification): $C_{2} H_{5} OH + C H_{3} COOH Acid catalyst C H_{3} COO C_{2} H_{5} + H_{2} O$
½ mark
Product: ethyl ethanoate, a sweet-smelling ester ( $C H_{3} COO C_{2} H_{5}$ ).
½ mark
(ii)(4) Oxidation by acidified potassium dichromate, which acts as an oxidising agent: $C H_{3} C H_{2} OH Acidified K_{2} C r_{2} O_{7} C H_{3} COOH$
½ mark
Product: ethanoic acid ( $C H_{3} COOH$ ).
½ mark

Answer: (i) Ethanol, C₂H₅OH; (ii) (1) sodium ethoxide + H₂; (2) ethene; (3) ethyl ethanoate (ester); (4) ethanoic acid

Where the marks are

Names ethanol (½ mark)
Writes its formula C₂H₅OH (½ mark)
Equation with Na (½ mark) and names sodium ethoxide (½ mark)
Equation of dehydration with excess conc. H₂SO₄ at 443 K (½ mark) and names ethene (½ mark)
Esterification equation (½ mark) and names the ester, ethyl ethanoate (½ mark)
Oxidation equation with acidified K₂Cr₂O₇ (½ mark) and names ethanoic acid (½ mark)

Revise the chapter

Chapter: Carbon and its Compounds (notes, formulas, where marks are lost and every past question)

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 31/2/1: 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.

CBSE Class 10 Science 2024: question 34(b)

Hints

Step-by-step solution

Revise the chapter

More questions from Carbon and its Compounds