JEE Main 2021 — Chemistry Inorganic Chemistry

2021integermedium

The spin-only magnetic moment value for the complex ${[\mathrm{Co}(\mathrm{CN}{)}_{6}]}^{4-}$ is...... $\mathrm{BM}$ . (nearest integer value)

[At. no. of $\mathrm{Co}=27$ ]

Official previous-year question

Held on 20 Jul 2021 · Verified 6 Jul 2026.

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Solution

${[\mathrm{Co}(\mathrm{CN}{)}_{6}]}^{4-}$

$x+6\times (-1)=-4$

$x=+2$

${\mathrm{Co}}^{2+}:[\mathrm{Ar}]3{d}^{7}$ and ${\mathrm{CN}}^{-}$ is a strong field ligand which can pair electron of central atom.

JEE Main 2021 Chemistry, Coordination Compounds — solution figure

It has one unpaired electron (n) in $4d-$ subshell. So spin only magnetic moment $(\mu )=$

$\sqrt{n(n+2)}B\cdot M$

where $n=$ number of unpaired electrons.

$\mu =\sqrt{3}$ $B.M$

$\mu =1.73\mathrm{BM}\simeq 2\mathrm{BM}$

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JEE Main Inorganic Chemistry in other years

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JEE Main 2021 — Chemistry Inorganic Chemistry

2021integermedium

The spin-only magnetic moment value for the complex ${[\mathrm{Co}(\mathrm{CN}{)}_{6}]}^{4-}$ is...... $\mathrm{BM}$ . (nearest integer value)

[At. no. of $\mathrm{Co}=27$ ]

Official previous-year question

Held on 20 Jul 2021 · Verified 6 Jul 2026.

Did you get this right?

Solution

${[\mathrm{Co}(\mathrm{CN}{)}_{6}]}^{4-}$

$x+6\times (-1)=-4$

$x=+2$

${\mathrm{Co}}^{2+}:[\mathrm{Ar}]3{d}^{7}$ and ${\mathrm{CN}}^{-}$ is a strong field ligand which can pair electron of central atom.

JEE Main 2021 Chemistry, Coordination Compounds — solution figure

It has one unpaired electron (n) in $4d-$ subshell. So spin only magnetic moment $(\mu )=$

$\sqrt{n(n+2)}B\cdot M$

where $n=$ number of unpaired electrons.

$\mu =\sqrt{3}$ $B.M$

$\mu =1.73\mathrm{BM}\simeq 2\mathrm{BM}$

Your note

JEE Main Inorganic Chemistry in other years

Keep practicing Inorganic Chemistry

Work through every JEE Main Inorganic Chemistry PYQ, year by year.

Browse all Chemistry topics

JEE Main 2021 — Chemistry Inorganic Chemistry

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

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Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry

JEE Main 2021 — Chemistry Inorganic Chemistry

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry