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Answer the following. (Class 12 Chemistry 2026, Q26)

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ChemistryCBSE Class 12 · Board exam 2026, set 56/5/1 · 3 marks · Short answer

CBSE Class 12 Chemistry 2026: question 26

Set in the CBSE Class 12 board exam of 2026, paper 56/5/1, section C, question 26, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q26 · 3 marks · Short answerCoordination Compounds

Answer the following.

  1. (a)

    A coordination compound is mixed with excess of solution, two moles of AgCl are precipitated per mole of the compound. Write the structural formula of the coordination compound.

    1 mark
  2. (b)

    Write the oxidation state and hybridisation of the central metal in the following complex :
    [Atomic number of Fe = 26]

    1 mark
  3. (c)

    Why is coloured ? [Atomic number of Ni = 28]

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 56/5/1.

Hints

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

Hint 1

Only chloride ions outside the square brackets precipitate with AgNO₃.

Hint 2

Water is a weak-field ligand; decide whether inner (n−1)d or outer nd orbitals are used.

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) Two moles of AgCl per mole means two are ionisable, i.e. outside the coordination sphere. The third Cl and five complete the coordination number 6. Structural formula: .

    1 mark

  2. (b) Oxidation state of Fe in : , so +3.

    ½ mark

  3. Fe³⁺ is . is a weak-field ligand, so the electrons do not pair and the outer 4d orbitals are used. Hybridisation: sp³d² (outer-orbital, high-spin, octahedral).

    ½ mark

  4. (c) Ni²⁺ is with two unpaired electrons. It absorbs light in the visible region, which promotes an electron from to (d–d transition). The complementary colour (green) is seen.

    1 mark

Answer: (a) [Cr(H₂O)₅Cl]Cl₂·H₂O; (b) +3, sp³d²; (c) d–d transition of unpaired 3d electrons (3d⁸)

Where the marks are

  • Correct structural formula [Cr(H₂O)₅Cl]Cl₂·H₂O (1 mark)
  • Oxidation state +3 (½ mark)
  • sp³d² hybridisation (½ mark)
  • Colour due to d–d transition / unpaired d electrons (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 paper2026 board paper, set 56/5/1: 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.