Assertion (A): [Mn(CN)_6]³- has a magnetic moment of two unpaired electrons while [MnCl_6]³- has a paramagnetic moment of four unpaired electrons. Reason (R): [Mn(CN)_6]³- is inner orbital complexes involving d²sp³ hybridisation, on the other hand, [MnCl_6]³- is outer orbital complexes involving sp³d² hybridisation. Select the most appropriate answer from the options given below: (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true but R is not the correct explanation of A. (C) A is true but R is false. (D) A is false but R is true.

ChemistryCBSE Class 12 · Sample paper, session 2024-25 · 1 mark · Assertion-reason

CBSE Class 12 Chemistry sample paper 2024-25: question 13

From the official CBSE sample question paper for 2024-25, section A, question 13, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q13 · 1 mark · Assertion-reasonCompetency-basedCoordination Compounds

Assertion (A): $[M n (C N)_{6}]^{3 -}$ has a magnetic moment of two unpaired electrons while $[M n C l_{6}]^{3 -}$ has a paramagnetic moment of four unpaired electrons.
Reason (R): $[M n (C N)_{6}]^{3 -}$ is inner orbital complexes involving $d^{2} s p^{3}$ hybridisation, on the other hand, $[M n C l_{6}]^{3 -}$ is outer orbital complexes involving $s p^{3} d^{2}$ hybridisation.

Select the most appropriate answer from the options given below:

(A)Both A and R are true and R is the correct explanation of A
(B)Both A and R are true but R is not the correct explanation of A.
(C)A is true but R is false.
(D)A is false but R is true.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

Write the d-electron count of Mn $^{3 +}$ .

Hint 2

Compare CN $^{-}$ and Cl $^{-}$ as field strength ligands.

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.

Mn $^{3 +}$ is $3 d^{4}$ . CN $^{-}$ is a strong field ligand, so the electrons pair as $t_{2 g}^{4}$ , leaving 2 unpaired. Two inner d orbitals are free, giving $d^{2} s p^{3}$ .
Cl $^{-}$ is a weak field ligand, so there is no pairing and 4 electrons stay unpaired. Outer d orbitals are used, giving $s p^{3} d^{2}$ . A and R are both true and R explains A. Option (A).
1 mark

Answer: Option (A)

Where the marks are

Links ligand strength and hybridisation to the unpaired electrons (1 mark)

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

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 2024-25: every question, by section.

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CBSE Class 12 Chemistry sample paper 2024-25: question 13

Hints

Step-by-step solution

Revise the chapter

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