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The metals produced by… (Class 10 Science 2024, Q37)

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ScienceCBSE Class 10 · Board exam 2024, set 31/1/1 · 4 marks · Case-based

CBSE Class 10 Science 2024: question 37

Set in the CBSE Class 10 board exam of 2024, paper 31/1/1, 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

The metals produced by various reduction processes are not very pure. They contain impurities, which must be removed to obtain pure metals. The most widely used method for refining impure metals is electrolytic refining.

  1. (i)

    What is the cathode and anode made of in the refining of copper by this process ?

    1 mark
  2. (ii)

    Name the solution used in the above process and write its formula.

    1 mark
  3. (iii)(A)

    How copper gets refined when electric current is passed in the electrolytic cell ?

    2 marks

  4. OR

    (iii)(B)

    You have two beakers 'A' and 'B' containing copper sulphate solution. What would you observe after about 2 hours if you dip a strip of zinc in beaker 'A' and a strip of silver in beaker 'B'? Give reason for your observations in each case.

    2 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/1/1.

Hints

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

Hint 1

In refining, the metal to be purified is made the electrode that dissolves.

Hint 2

The electrolyte must contain ions of the same metal being refined.

Hint 3

For the beakers, compare the positions of Zn, Cu and Ag in the reactivity series.

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. (i) Cathode: a thin strip of pure copper; Anode: a thick block of impure copper.

    1 mark

  2. (ii) Electrolyte: acidified copper sulphate solution, formula .

    1 mark

  3. (iii)(A) On passing current, copper from the impure anode dissolves into the electrolyte as ions and an equal amount of pure copper from the electrolyte is deposited on the cathode:
    Anode: ; Cathode: (pure).

    1 mark

  4. The soluble impurities go into the solution, while the insoluble impurities settle at the bottom below the anode as anode mud. Thus pure copper collects on the cathode.

    1 mark

  5. (iii)(B) Beaker A (zinc strip): the blue colour of the solution fades and becomes colourless; reddish-brown copper deposits on the zinc strip.

    ½ mark

  6. Reason: zinc is more reactive than copper, so it displaces copper: .

    ½ mark

  7. Beaker B (silver strip): no change is observed; the solution stays blue.

    ½ mark

  8. Reason: silver is less reactive than copper, so it cannot displace copper from copper sulphate.

    ½ mark

Answer: (i) Cathode – pure Cu, anode – impure Cu; (ii) acidified copper sulphate, CuSO₄; (iii)(A) anode Cu dissolves, pure Cu deposits on cathode, impurities form anode mud; (iii)(B) A: blue colour fades (Zn more reactive); B: no change (Ag less reactive)

Where the marks are

  • Cathode pure copper, anode impure copper (½ + ½ mark)
  • Acidified copper sulphate and formula CuSO₄ (½ + ½ mark)
  • (iii)(A) Anode copper dissolves and pure copper deposits on cathode, with electrode reactions (1 mark)
  • (iii)(A) Soluble impurities in solution, insoluble ones settle as anode mud (1 mark)
  • (iii)(B) Observation and reason for beaker A (½ + ½ mark)
  • (iii)(B) Observation and reason for beaker B (½ + 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 paper2024 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.