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The emission of brown fumes in… (Class 10 Science 2023, Q2)

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ScienceCBSE Class 10 · Board exam 2023, set 31/1/1 · 1 mark · MCQ

CBSE Class 10 Science 2023: question 2

Set in the CBSE Class 10 board exam of 2023, paper 31/1/1, section A, question 2, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q2 · 1 mark · MCQCompetency-basedChemical Reactions and Equations

The emission of brown fumes in the given experimental set-up is due to

  1. (A)thermal decomposition of lead nitrate which produces brown fumes of nitrogen dioxide.
  2. (B)thermal decomposition of lead nitrate which produces brown fumes of lead oxide.
  3. (C)oxidation of lead nitrate forming lead oxide and nitrogen dioxide.
  4. (D)oxidation of lead nitrate forming lead oxide and oxygen.

Figure in the paper: A test tube held with tongs, inclined, containing lead nitrate being heated by a burner; brown fumes are emitted from the mouth of the test tube. Labels: Brown fumes, Lead nitrate, Burner. See it in the official paper.

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

Hints

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

Hint 1

Is heating a single compound to break it apart an oxidation or a decomposition?

Hint 2

Which product of this reaction is a brown gas?

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. On heating, lead nitrate breaks down into simpler substances. This is thermal decomposition, not oxidation:

  2. The brown fumes are nitrogen dioxide (). Lead oxide is a yellow solid and oxygen is colourless. So the answer is (A).

    1 mark

Answer: Option (A)

Where the marks are

  • Identifies brown fumes as from thermal decomposition, option (A) (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 paper2023 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.