Question

(A) A d1 octahedral complex is found to absorb visible light, with the absorption maximum occurring at 519 nm. Calculate the crystal-field splitting energy, Δ , in kJ/mol.

(b)If the complex has a formula of [M(H2O)6]3 , what effect would replacing the 6 aqua ligands with 6 F– ligands have on Δ? WIll delta increase, decrease, or remain constant?

Answer 1

a)

Given:
lambda = 5.19*10^-7 m

Find energy of 1 photon first

Given:
lambda = 5.19*10^-7 m

use:
E = h*c/lambda
=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(5.19*10^-7 m)
= 3.83*10^-19 J
This is energy of 1 photon

Energy of 1 mol = energy of 1 photon * Avogadro's number
= 3.83*10^-19*6.022*10^23 J/mol
= 2.306*10^5 J/mol
= 231 KJ/mol
Answer: 231 KJ/mol

b)
F- is weak field ligand as compared to H2O
So, splitting would be less
So, delta will decrease
Answer: decrease