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← JEE Main 2022 · 25 Jun · Shift 1
ChemistryInteger+4 / -1Question 89 of 90

JEE Main 2022 · 25 Jun · Shift 1, Chemistry question 89

If [Cu(H2O)4]2+\mathrm{[Cu(H_2O)_4]^{2+}} absorbs a light of wavelength 600 nm for d-d transition, then the value of octahedral crystal field splitting energy for [Cu(H2O)6]2+\mathrm{[Cu(H_2O)_6]^{2+}} will be ______ ×10−21\times10^{-21} J. [Nearest integer]

(Given : h=6.63×10−34h=6.63\times10^{-34} Js and c=3.08×108 ms−1c=3.08\times10^8\ \mathrm{ms^{-1}})

Answer and worked solution

Official answer: 746

Tetrahedral splitting. Δt=hcλ\Delta_t=\dfrac{hc}\lambda. With c=3.0×108c=3.0\times10^8: Δt=6.63×10−34×3×108600×10−9=3.315×10−19\Delta_t=\dfrac{6.63\times10^{-34}\times3\times10^8}{600\times10^{-9}}=3.315\times10^{-19} J.

Octahedral. Δo=94Δt≈7.46×10−19\Delta_o=\frac94\Delta_t\approx7.46\times10^{-19} J =746×10−21=746\times10^{-21} J.

Note. The paper prints c=3.08×108c=3.08\times10^8 m s−1^{-1}, which would give about 766; the keyed 746 uses 3.0×1083.0\times10^8.

Answer: 746

Topics:Crystal field theory
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