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Write the reactions of… (Class 12 Chemistry 2026, Q25)

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ChemistryCBSE Class 12 · Board exam 2026, set 56/1/1 · 3 marks · Short answer

CBSE Class 12 Chemistry 2026: question 25

Set in the CBSE Class 12 board exam of 2026, paper 56/1/1, section C, question 25, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q25 · 3 marks · Short answerBiomolecules

Write the reactions of D-Glucose with the following :
(a) HI
(b) water
(c) Conc.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 56/1/1.

Hints

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

Hint 1

HI is a strong reducing agent; bromine water and nitric acid are oxidising agents.

Hint 2

Bromine water oxidises only the aldehyde group; conc. HNO₃ oxidises the primary alcohol group as well.

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) Prolonged heating with HI reduces glucose to n-hexane, showing that its six C atoms are in a straight chain:

    1 mark

  2. (b) The mild oxidant bromine water oxidises the –CHO group to give gluconic acid:

    1 mark

  3. (c) Conc. oxidises both the –CHO and the terminal –CH₂OH groups to –COOH, giving saccharic (glucaric) acid:

    1 mark

Answer: (a) n-hexane; (b) gluconic acid; (c) saccharic acid

Where the marks are

  • Reaction with HI giving n-hexane (1 mark)
  • Reaction with Br₂ water giving gluconic acid (1 mark)
  • Reaction with conc. HNO₃ giving saccharic acid (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Biomolecules, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 56/1/1: 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.