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How is ozone formed in the… (Class 10 Science 2023, Q33)

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ScienceCBSE Class 10 · Board exam 2023, set 31/5/1 · 3 marks · Short answer

CBSE Class 10 Science 2023: question 33

Set in the CBSE Class 10 board exam of 2023, paper 31/5/1, section C, question 33, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q33 · 3 marks · Short answerOur Environment

How is ozone formed in the higher levels of the atmosphere ? "Damage to the ozone layer is a cause of concern." Justify this statement.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/5/1.

Hints

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

Hint 1

Ozone is O₃ and ordinary oxygen is O₂. What must first break apart?

Hint 2

What supplies the energy to break O₂ in the upper atmosphere?

Hint 3

What does the ozone layer protect us from?

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. Formation: in the upper atmosphere, high-energy UV radiation splits oxygen molecules into free (nascent) oxygen atoms:

    1 mark

  2. These free oxygen atoms combine with oxygen molecules to form ozone:

    1 mark

  3. Justification: the ozone layer absorbs harmful UV radiation from the Sun. If it is damaged (for example by CFCs), more UV radiation reaches the Earth and causes harm such as skin cancer in human beings.

    1 mark

Answer: UV splits O₂ into O atoms, which combine with O₂ to form O₃; damage lets UV reach the Earth, causing skin cancer and other harm

Where the marks are

  • UV splits O₂ into oxygen atoms (1 mark)
  • O + O₂ → O₃ (1 mark)
  • Damage lets harmful UV reach the Earth, e.g. skin cancer (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Our Environment, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/5/1: 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.