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An acid 'X' and an alcohol… (Class 10 Science 2023, Q34a)

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ScienceCBSE Class 10 · Board exam 2023, set 31/2/1 · 5 marks · Long answer

CBSE Class 10 Science 2023: question 34(a)

Set in the CBSE Class 10 board exam of 2023, paper 31/2/1, section D, question 34(a), for 5 marks. Try it first; the hints and our step-by-step solution are below.

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

An acid 'X' and an alcohol 'Y' react with each other in the presence of an acid catalyst to form a sweet smelling substance 'Z'. Identify 'X', 'Y' and 'Z'. Write the chemical equation for the reaction involved and name it. The substance 'Z' on treatment with sodium hydroxide produces back the alcohol 'Y' and sodium ethanoate. Write the chemical equation for the reaction involved and name it, giving justification for the name.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/2/1.

Hints

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

Hint 1

Sweet-smelling compounds formed from an acid and an alcohol belong to which family?

Hint 2

Sodium ethanoate is produced, so the acid must contain two carbon atoms.

Hint 3

Base hydrolysis of esters is used in a common household product. Which one?

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. X is ethanoic acid (acetic acid), .

    ½ mark

  2. Y is ethanol, .

    ½ mark

  3. Z is ethyl ethanoate, , a sweet-smelling ester.

    ½ mark

  4. 1 mark

  5. This reaction is called esterification.

    ½ mark

  6. 1 mark

  7. This reaction is called saponification.

    ½ mark

  8. Justification: hydrolysis of an ester by an alkali gives the alcohol and the sodium salt of the acid. The same reaction is used to make soap from fats and oils, hence the name saponification.

    ½ mark

Answer: X = CH₃COOH (ethanoic acid), Y = C₂H₅OH (ethanol), Z = CH₃COOC₂H₅ (ethyl ethanoate); esterification; saponification (used in making soap)

Where the marks are

  • Identifies X, Y and Z (½ mark each)
  • Equation for esterification (1 mark)
  • Names esterification (½ mark)
  • Equation of ester with NaOH (1 mark)
  • Names saponification (½ mark)
  • Justification: the reaction is used in preparing soap (½ 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 paper2023 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.