JEE Main 2025 Apr 2 Shift 1, Chemistry Q15: Colour, Magnetism And Stability Of Co-ordination Compounds

JEE Main2025Apr 2, Shift 1Chemistry

Given below are two statements :

Statement (I) : In octahedral complexes, when $Δ_{o} < P$ high spin complexes are formed. When $Δ_{o} > P$ low spin complexes are formed.

Statement (II) : In tetrahedral complexes because of $Δ_{t} < P$ , low spin complexes are rarely formed.

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

A
Statement I is correct but Statement II is incorrect.
B
Both Statement I and Statement II are incorrect
C
Statement I is incorrect but Statement II is correct
D
Both Statement I and Statement II are correct

Solution

Whether an octahedral complex is high spin or low spin is decided by comparing the crystal-field splitting $Δ_{o}$ with the pairing energy $P$ :

If $Δ_{o} < P$ : pairing costs more than promotion to $e_{g}$ , so electrons spread out — high spin.

If $Δ_{o} > P$ : it is cheaper to pair in $t_{2 g}$ — low spin.

Statement I is therefore correct.

For a tetrahedral geometry, $Δ_{t} \approx \frac{4}{9} Δ_{o}$ , which is almost always smaller than $P$ . Pairing is rarely favoured, so tetrahedral complexes are almost always high spin, and low-spin tetrahedral complexes are rare.

Statement II is therefore also correct.

$∴$ Option (4) is correct.

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JEE Main 2025 Apr 2 Shift 1, Chemistry Q15: Colour, Magnetism And Stability Of Co-ordination Compounds

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