Answer the following. (a) Write the IUPAC name of the following complex : K_3[Cr(C_2O_4)_3] (b) Differentiate between homoleptic complex and heterolyptic complex. (c) Which type of isomerism is exhibited by the following complex : [Pt(NH_3)_2Cl_2]

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

CBSE Class 12 Chemistry 2026: question 25

Set in the CBSE Class 12 board exam of 2026, paper 56/5/1, section C, question 25, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q25 · 3 marks · Short answerCoordination Compounds

Answer the following.

(a)
Write the IUPAC name of the following complex : $K_{3} [Cr (C_{2} O_{4})_{3}]$
1 mark
(b)
Differentiate between homoleptic complex and heterolyptic complex.
1 mark
(c)
Which type of isomerism is exhibited by the following complex : $[Pt (N H_{3})_{2} C l_{2}]$
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

Oxalate as a ligand is 'oxalato'; work out the oxidation state of Cr from the three K⁺ ions.

Hint 2

For a square planar $M A_{2} B_{2}$ complex, think about whether like ligands sit side by side or opposite each other.

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.

(a) $K_{3} [Cr (C_{2} O_{4})_{3}]$ : Potassium trioxalatochromate(III).
1 mark
(b) In a homoleptic complex the metal is bound to only one kind of donor group, e.g. $[Co (N H_{3})_{6}]^{3 +}$ . In a heteroleptic complex the metal is bound to more than one kind of donor group, e.g. $[Co (N H_{3})_{4} C l_{2}]^{+}$ .
1 mark
(c) Square planar $[Pt (N H_{3})_{2} C l_{2}]$ (type $M A_{2} B_{2}$ ) shows geometrical (cis–trans) isomerism.
1 mark

Answer: (a) Potassium trioxalatochromate(III); (b) one kind vs more than one kind of ligand; (c) geometrical (cis–trans) isomerism

Where the marks are

Correct IUPAC name (1 mark)
Correct distinction between homoleptic and heteroleptic (1 mark)
Geometrical / cis–trans isomerism (1 mark)

Revise the chapter

Chapter: Coordination Compounds (notes, formulas, where marks are lost and every past question)
Topic: IUPAC Nomenclature of Coordination Compounds

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.

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CBSE Class 12 Chemistry 2026: question 25

Hints

Step-by-step solution

Revise the chapter

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