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Metals are required for a… (Class 10 Science 2023, Q37)

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ScienceCBSE Class 10 · Board exam 2023, set 31/5/1 · 4 marks · Case-based

CBSE Class 10 Science 2023: question 37

Set in the CBSE Class 10 board exam of 2023, paper 31/5/1, section E, question 37, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q37 · 4 marks · Case-basedCompetency-basedMetals and Non-metals

Metals are required for a variety of purposes. For this we need their extraction from their ores. Ores mined from the earth are usually contaminated with many impurities which must be removed prior to the extraction of metals. The extraction of pure metal involves the following steps : (1) Concentration of ore (2) Extraction of the metal from the concentrated ore (3) Refining of the metal

  1. (a)

    Name an ore of Mercury and state the form in which Mercury is present in it.

    1 mark
  2. (b)

    What happens to zinc carbonate when it is heated strongly in a limited supply of air ?

    1 mark
  3. (c)

    The reaction of a metal A with is highly exothermic and is used to join railway tracks. (I) Identify the metal A and name the reaction taking place. (II) Write the chemical equation for the reaction of metal A with .

    2 marks
  4. (c)

    We cannot use carbon to obtain sodium from sodium oxide. Why ? State the reactions taking place at cathode and anode during electrolytic reduction of sodium chloride.

    2 marks

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

Mercury is extracted from a sulphide ore whose name begins with 'C'.

Hint 2

Heating a carbonate ore in limited air is calcination. Which gas is given off?

Hint 3

For (c), think of which highly reactive metal reduces iron oxide and produces enough heat to melt the iron.

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) The ore of mercury is cinnabar, . Mercury is present in it in the sulphide form.

    1 mark

  2. (b) Heating strongly in a limited supply of air is called calcination. Zinc carbonate decomposes into zinc oxide and carbon dioxide:

    1 mark

  3. (c)(I) Metal A is aluminium. The reaction is the thermit reaction.

    1 mark

  4. (c)(II)
    The molten iron produced is used to join railway tracks.

    1 mark

  5. (c) OR: Sodium is highly reactive and has a greater affinity for oxygen than carbon has. Carbon therefore cannot reduce sodium oxide to sodium, so sodium is obtained by electrolytic reduction of molten NaCl.

    1 mark

  6. At the cathode:

    ½ mark

  7. At the anode:

    ½ mark

Answer: (a) Cinnabar, HgS (sulphide form); (b) it changes to ZnO and CO₂ (calcination); (c) (I) aluminium, thermit reaction; (II) Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat. OR (c): Na has more affinity for oxygen than C; cathode Na⁺ + e⁻ → Na; anode 2Cl⁻ → Cl₂ + 2e⁻

Where the marks are

  • Names cinnabar and states that Hg is present as the sulphide, HgS (½ + ½ mark)
  • States that ZnO is formed (calcination), with the equation ZnCO₃ → ZnO + CO₂ (1 mark)
  • Identifies A as aluminium and names the thermit reaction (½ + ½ mark)
  • Writes the balanced equation Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat (1 mark)
  • OR: explains that sodium is more reactive and has more affinity for oxygen than carbon (1 mark)
  • OR: cathode reaction Na⁺ + e⁻ → Na (½ mark)
  • OR: anode reaction 2Cl⁻ → Cl₂ + 2e⁻ (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 31/5/1: 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.