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Account for the following… (Class 10 Science 2026, Q26)

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ScienceCBSE Class 10 · Board exam 2026, set 31/4/1 · 3 marks · Short answer

CBSE Class 10 Science 2026: question 26

Set in the CBSE Class 10 board exam of 2026, paper 31/4/1, section B, question 26, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q26 · 3 marks · Short answerChemical Reactions and Equations

Account for the following:
(a) White silver chloride turns grey when exposed to sunlight.
(b) Lead (II) nitrate on heating releases brown fumes.
(c) Bags of oil and fat containing food items are flushed with nitrogen gas.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/4/1.

Hints

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

Hint 1

All three involve either decomposition or oxidation. Which one is which?

Hint 2

Grey colour comes from a metal, and brown fumes come from an oxide of nitrogen.

Hint 3

What spoils oily food when it is left exposed to air?

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) Sunlight decomposes silver chloride into grey silver metal and chlorine gas (photolytic decomposition):

    1 mark

  2. (b) On heating, lead(II) nitrate decomposes and gives off nitrogen dioxide, which is seen as brown fumes:

    1 mark

  3. (c) Nitrogen is unreactive and displaces oxygen from the bag. This prevents oxidation of the oils and fats, so the food does not become rancid and its taste and smell are kept.

    1 mark

Answer: (a) AgCl decomposes in sunlight into grey Ag and Cl. (b) Pb(NO) decomposes to give brown NO gas. (c) Nitrogen prevents oxidation (rancidity) of fats and oils.

Where the marks are

  • Explains the decomposition of AgCl to form silver in sunlight (1 mark)
  • Identifies the brown fumes as NO from decomposition of lead nitrate (1 mark)
  • States that nitrogen prevents oxidation or rancidity of fats (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Chemical Reactions and Equations, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/4/1: 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.