Question

A d1 octahedral complex is found to absorb visible light, with the absorption maximum occurring at 505 nm. Calculate the crystal-field splitting energy, Δ , in kJ/mol.

Answer 1

we know that

Energy is given by

E = h x c / lamda

now

lamda = wavelength = 505 nm

lamda = 505 x 10-9 m

h = plancks constant = 6.626 x 10-34

c= speed of light = 3 x 10^8

so

E = 6.626 x 10-34 x 3 x 10^8 / 505 x 10-9

E = 3.936 x 10-19

now

this energy is only for one atom

we know that

1 mole of a compound contains avagadro number of atooms

so

energy per mole = energy per atom x avagadro number

so

energy per mole = 3.936 x 10-19 x 6.023 x 10^23

energy per mole = 237079 J

energy per mole = 237.079 kJ

so

the energy is 237.079 kJ/mol