Coordination Compounds 2 Question 22

####24. Two complexes [Cr(H2O)6]Cl3(A) and [Cr(NH3)6]Cl3(B) are violet and yellow coloured, respectively. The incorrect statement regarding them is

(2019 Main, 9 Jan I)

(a) Δo value for (A) is less than that of (B)

(b) both absorb energies corresponding to their complementary colours

(c) Δo values of (A) and (B) are calculated from the energies of violet and yellow light, respectively

(d) both are paramagnetic with three unpaired electrons

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Answer:

Correct Answer: 24. (d)

Solution:

  1. A ’ absorbs yellow light of less energy and emits violet light of high energy (complementary colour) because H2O is a weak field ligand. But in case of ’ B ‘, due to presence of strong field ligand (NH3), it absorbs high energy violet light and emits low energy complementary yellow colour.

Δ (CFSE) is measured with help of wavelength of the colour absorbed by the given coordination compound, as

ΔO=hv=h×cλ

Both the complexes contain three unpaired electrons. Therefore, both are paramagnetic.



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