a d^1 octahedral complex is found to absorb visible light, with the absorption m

Question

a d^1 octahedral complex is found to absorb visible light, with the absorption maximum occuring at 511 nm.

a) calculate the crystal-field splitting energy, delta, in kj/mol.

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:

b) delta?: 1.delta will increase, 2. delta will decrease. 3. delta will remain constant.

c) the observed color complex? 1. color shifts toward a longer wavelenght, 2. there is no effect on color. 3. color shifts toward a shorter wavelength.

Explanation / Answer

first, calculate the energy that corresponds to the wavelength in question

C = wavelength x frequency
E = planck's constant x frequency, C = speed of light = 3x10^8m/s
planck's constant = 6.626x10-34J-s
wavelength is in meters.....take nm and either divide by 1x10^9nm/m or add "x10^-9" after the number, example 244nm = 244x10^-9m, shortcut
so
C / wavelength = E / planck's constant
solving for E, we get E = C x planck's constant / wavelength
E = 3x10^8m/s x 6.626x10^-34J-s / 244x10^-9m = 8.147x10^-16J

next, convert J/ion to kJ/mole
8.147x10^-16J/ion x 6.022x10^23 ions/mole / 1000J/kJ = 4.902x10^5kJ

do this for the other 2 wavelengths
comparison of periods Co = 3rd, Rh = 4th, Ir = 5. Ir > Rh > Co in size

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