Question 22.8: Crystal Field Splitting Energy The complex ion [Cu(NH3)6]2+ ...
Crystal Field Splitting Energy
The complex ion [Cu(NH_3)_6]^{2+} is blue in aqueous solution. Estimate the crystal field splitting energy (in kJ /mol) for this ion.
Begin by consulting the color wheel (Figure 22.15) to determine approximately what wavelength is being absorbed.
Because the solution is blue, you can deduce that orange light is absorbed since orange is the complementary color to blue.
Estimate the absorbed wavelength. The color orange ranges from 580 to 650 nm, so you can estimate the average wavelength as 615 nm.
Calculate the energy corresponding to this wavelength, using E = hc/λ . This energy corresponds to ∆
E=\frac{(6.626 \times 10^{-34} J .\cancel{s})(3.00 \times 10^8 \cancel{m}/\cancel{s})}{(615 \cancel{nm})(1 \times 10^{-9} \cancel{m}.\cancel{nm})}
E = 3.23 \times 10^{-19} / J = ∆Convert J/ion into kJ/mol.
\Delta =\frac{(3.23 \times 10^{-19} \cancel{J}/\cancel{ion})(6.02 \times 10^{23} \cancel{ion}/mol)}{(1000 \cancel{J}/kJ)}
∆ = 195 kJ/mol
