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With the help of suitable… (Class 10 Science 2023, Q28)

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ScienceCBSE Class 10 · Board exam 2023, set 31/2/1 · 3 marks · Short answer

CBSE Class 10 Science 2023: question 28

Set in the CBSE Class 10 board exam of 2023, paper 31/2/1, section C, question 28, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q28 · 3 marks · Short answerMetals and Non-metals

With the help of suitable chemical equations, list the two main differences between roasting and calcination. How is metal reduced from the product obtained after roasting/calcination of the ore ? Write the chemical equation for the reaction involved.

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

One process is for ores containing sulphur, the other for carbonates.

Hint 2

Compare how much air is supplied in each process.

Hint 3

Both give a metal oxide. Which cheap reducing agent converts zinc oxide to zinc?

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. Difference 1: Roasting is done for sulphide ores, while calcination is done for carbonate ores.

    ½ mark

  2. Difference 2: In roasting, the ore is heated strongly in excess of air. In calcination, the ore is heated strongly in the absence or limited supply of air.

    ½ mark

  3. Equations:

    • Roasting:
    • Calcination:
    1 mark

  4. Reduction: The metal oxide obtained is reduced to the metal by heating it with a reducing agent such as carbon (coke).

    ½ mark

  5. ½ mark

Answer: Roasting: sulphide ores, excess air (2ZnS + 3O₂ → 2ZnO + 2SO₂). Calcination: carbonate ores, limited/no air (ZnCO₃ → ZnO + CO₂). The oxide is reduced by carbon: ZnO + C → Zn + CO.

Where the marks are

  • Difference based on type of ore (½ mark)
  • Difference based on supply of air (½ mark)
  • Correct roasting and calcination equations (½ + ½ mark)
  • Reduction of the oxide using carbon (½ mark)
  • Correct reduction equation (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Metals and Non-metals, 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.