Question

Estimate the crystal field stabilization energy for the octahedral ion hexaaquachromium(III) , if the wavelength of maximum absorption for the ion is 575 nm.   
________kJ mol^-1

Answer 1

Similar questions done this many time before please pardon

The absorption spectrum of the complex ion [Rh(NH3)6]^3+ has maximum absorbance at 295 nm, calculate the crystal field splitting energy (in kJ/mol) for this ion

E = (h X c) / lambda

where h = plancks constant = 6.626 X 10^-34 j s

c = velocity of light = 3 X 10^8 m/s

lambda = wavelength = 295 nm = 295 X 10^-9 m

so E = ( 6.626 X 10^-34 X 3 X 10^8) / 295 X 10^-9

E = 1.988 X 10^-25 / 295 X 10^-9

E = 6.739 X 10^-19 j

so for 1 ion .....energy is 6.739 X 10^-19 j

so for 6.022 X 10^23 ions ( 1 mole) ...energy is 6.739 X 10^-19 X 6.022 X 10^23 = 40.582 X 10^4 j/mole

in order to get the value in kj/mole divide it by 1000...

40.582 X 10^4/1000 = 405.82 kj/mole