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Answer the following. (Class 12 Chemistry SQP 2023-24, Q22)

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ChemistryCBSE Class 12 · Sample paper, session 2023-24 · 3 marks · Short answer

CBSE Class 12 Chemistry sample paper 2023-24: question 22

From the official CBSE sample question paper for 2023-24, section C, question 22, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q22 · 3 marks · Short answerCoordination Compounds

Answer the following.

  1. (a)

    Write the formula for the following coordination compound
    Bis(ethane-1,2-diamine) dihydroxidochromium(III) chloride

    0 marks
  2. (b)

    Does ionization isomer for the following compound exist? Justify your answer.

    0 marks
  3. (c)

    Is the central metal atom in coordination complexes a Lewis acid or a Lewis base? Explain.

    0 marks

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.

Hints

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

Hint 1

Balance the charges: Cr(III), two neutral en, two OH⁻ and the chloride counter ion.

Hint 2

Ionisation isomers exchange a ligand with the ion outside the square bracket. What is outside here?

Hint 3

Ligands donate lone pairs, so what must the metal be doing?

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) , i.e. . Check: Cr is +3, two OH⁻ give –2, so the complex ion is +1 and needs one Cl⁻.

    1 mark

  2. (b) No. Ionisation isomers arise when a ligand inside the coordination sphere swaps places with a counter ion outside it. Here the ion outside the sphere is Hg²⁺, a metal cation that cannot act as a ligand, so no such exchange (and no ionisation isomer) is possible.

    1 mark

  3. (c) The central metal atom/ion is a Lewis acid. It accepts lone pairs of electrons from the ligands (Lewis bases) into its vacant orbitals, forming coordinate bonds.

    1 mark

Answer: (a) [Cr(en)₂(OH)₂]Cl; (b) No – the counter ion Hg²⁺ cannot exchange with a ligand; (c) Lewis acid (electron-pair acceptor)

Where the marks are

  • Correct formula [Cr(en)₂(OH)₂]Cl (1 mark)
  • No ionisation isomer, since only a ligand–counter-ion exchange gives one and Hg²⁺ is not a ligand (1 mark)
  • Lewis acid, as it accepts electron pairs from ligands (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Coordination Compounds, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2023-24: 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.