JEE Main 2025 — Chemistry Inorganic Chemistry

2025mcqeasy

Which one of the following complexes will have $\Delta_0=0$ and $\mu=5.96$ B.M.?

Official previous-year question

Held on 4 Apr 2025 · Verified 6 Jul 2026.

Options

A
$\left[\mathrm{Fe}(\mathrm{CN})_6\right]^4$
B
$\left[\mathrm{CO}\left(\mathrm{NH}_3\right)_6\right]^{3+}$
C
$\left[\mathrm{FeF}_6\right]^4$
D
$\left[\mathrm{Mn}(\mathrm{SCN})_6\right]^4$

Did you get this right?

Solution

(1) $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} \quad \mathrm{Co}^{3+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0$

JEE Main 2025 Chemistry, Coordination Compounds — solution figure 1

$=[-0.4 \times 6+0.6 \times(0)] \Delta_0=-2.4 \Delta_0$

(2)

$\begin{aligned}
& {\left[\mathrm{Mn}(\mathrm{SCN})_6\right]^4} \

& \mathrm{Mn}^{2+} \Rightarrow 3 \mathrm{d}^5 4 \mathrm{s}^0
\end{aligned}$ JEE Main 2025 Chemistry, Coordination Compounds — solution figure 2

$\begin{aligned}
& \mu=\sqrt{35} \text { B.M. }=5.96 \text { B.M. } \

& \mathrm{CFSE}=(-0.4 \times 3+0.6 \times 2) \Delta_0
\end{aligned}$

So $\Delta_0=0$

(3)

$\begin{aligned}<br />& {\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{-4} \quad \mathrm{Fe}^{2+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0}<br />\end{aligned}$ JEE Main 2025 Chemistry, Coordination Compounds — solution figure 3

$\mathrm{CFSE}=-2.4 \Delta_0$

(4) $\left[\mathrm{FeF}_6\right]^{4-}$

$\mathrm{Fe}^{2+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0$ JEE Main 2025 Chemistry, Coordination Compounds — solution figure 4

$\begin{aligned}
& \mu=\sqrt{24} \text { B.M. }=4.89 \text { B.M. } \

& \text { CFSE }=(-0.4 \times 4+0.6 \times 2) \Delta_0=-1.2 \Delta_0
\end{aligned}$

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JEE Main 2025 — Chemistry Inorganic Chemistry

2025mcqeasy

Which one of the following complexes will have $\Delta_0=0$ and $\mu=5.96$ B.M.?

Official previous-year question

Held on 4 Apr 2025 · Verified 6 Jul 2026.

Options

A
$\left[\mathrm{Fe}(\mathrm{CN})_6\right]^4$
B
$\left[\mathrm{CO}\left(\mathrm{NH}_3\right)_6\right]^{3+}$
C
$\left[\mathrm{FeF}_6\right]^4$
D
$\left[\mathrm{Mn}(\mathrm{SCN})_6\right]^4$

Did you get this right?

Solution

(1) $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} \quad \mathrm{Co}^{3+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0$

JEE Main 2025 Chemistry, Coordination Compounds — solution figure 1

$=[-0.4 \times 6+0.6 \times(0)] \Delta_0=-2.4 \Delta_0$

(2)

$\begin{aligned}
& {\left[\mathrm{Mn}(\mathrm{SCN})_6\right]^4} \

& \mathrm{Mn}^{2+} \Rightarrow 3 \mathrm{d}^5 4 \mathrm{s}^0
\end{aligned}$ JEE Main 2025 Chemistry, Coordination Compounds — solution figure 2

$\begin{aligned}
& \mu=\sqrt{35} \text { B.M. }=5.96 \text { B.M. } \

& \mathrm{CFSE}=(-0.4 \times 3+0.6 \times 2) \Delta_0
\end{aligned}$

So $\Delta_0=0$

(3)

$\mathrm{CFSE}=-2.4 \Delta_0$

(4) $\left[\mathrm{FeF}_6\right]^{4-}$

$\mathrm{Fe}^{2+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0$ JEE Main 2025 Chemistry, Coordination Compounds — solution figure 4

$\begin{aligned}
& \mu=\sqrt{24} \text { B.M. }=4.89 \text { B.M. } \

& \text { CFSE }=(-0.4 \times 4+0.6 \times 2) \Delta_0=-1.2 \Delta_0
\end{aligned}$

JEE Main 2025 — Chemistry Inorganic Chemistry

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JEE Main 2025 — Chemistry Inorganic Chemistry

Options

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