Given below are two statements : Statement I: Both [ Co ( NH 3 ) 6 ] 3+ and [ CoF ] 3- complexes are octahedral but differ in their magnetic behaviour. Statement II: [ Co ( NH 3 ) 6 ] 3+ is diamagnetic whereas [ CoF 6 ] 3- is paramagnetic. In the light of the above statements, choose the correct answer from the options given below:

Both Statement I and Statement II are true

Both Statement I and Statement II are false

Statement I is true but Statement II is false

Statement I is false but Statement II is true

Chemistry · Coordination Compounds

NEET (UG) 2024 — Question 68

Given below are two statements :

Statement I: Both $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}$ and $[\mathrm{CoF}]^{3-}$ complexes are octahedral but differ in their magnetic behaviour.

Statement II: $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}$ is diamagnetic whereas $\left[\mathrm{CoF}_{6}\right]^{3-}$ is paramagnetic.

In the light of the above statements, choose the correct answer from the options given below:

Option A:
Both Statement I and Statement II are true
Correct
Option B:
Both Statement I and Statement II are false
Option C:
Statement I is true but Statement II is false
Option D:
Statement I is false but Statement II is true

Answer: A

Step-by-step solution

In $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}, \mathrm{Co}^{3+}$ ion is having $3 \mathrm{~d}^{6}$ configuration.

Electronic configuration of $\mathrm{Co}^{3+}:$

In presence of $\mathrm{NH}_{3}$ ligand, pairing of electrons takes place and it becomes diamagnetic complex ion.

In presence of $\mathrm{NH}_{3}$ ligand :

$\therefore \quad\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}$ is octahedral with $\mathrm{d}^{2} \mathrm{sp}^{3}$ hybridisation and it is diamagnetic in nature.

In case of $\left[\mathrm{CoF}_{6}\right]^{3-}, \mathrm{Co}$ is in +3 oxidation state and it is having $3 \mathrm{~d}^{6}$ configuration.

In presence of weak field $\mathrm{F}^{-}$ ligand, pairing does not take place.

In presence of $\mathrm{F}^{-}$ ligands :

$\therefore \quad$ In $\left[\mathrm{CoF}_{6}\right]^{3-}, \mathrm{Co}^{3+}$ is $\mathrm{sp}^{3} \mathrm{~d}^{2}$ hybridised with four unpaired electrons, so it is

paramagnetic in nature.

Answer key and solution verified before publishing.

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Exam: NEET (UG) 2024
Paper: 2024 paper
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Properties and importance of Coordination Complexes

Answer: A

Step-by-step solution

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