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 occurring at 503 nm. Calculate the crystal -field splitting energy, delta, in kJ/mol.. Incorrect. Energy, E, is related to wavelength, lambda, by where h is Planck's constant, h = 6.626 times 10^-34 J - s, and c is the speed of light, c = 2.998 times 10^8 m/s. If the complex has a formula of [M(H_2O)_6]^3+, what effect would replacing the 6 aqua ligands with 6 Cal ligands have on delta? delta will decrease delta will increase delta will remain constant

Explanation / Answer

The octahedral complex has 2 sets of d orbitals based on their relative energies, t2g and eg. d1 octahedral complex absorbs light of wavelength = 503 nm = 503 * 10^-9 m

After absorbing the energy, the single electron goes from ground state (t2g) to excited state (eg) and that energy difference between the ground state and excite state (difference in t2g and eg orbitals) is called the crystal field splitting energy.

Here, the ground state configuration t2g^1 eg^0 h t2g^0 eg^1 (excited state), hence the transition energy is therefore a direct measure of i.e. the crystal field splitting energy

So, crystal field splitting energy per photon = hc/ = (6.626 * 10^-34 J . s * 2.998 * 10^8 m/s)/503 * 10^-9 m = 3.95 * 10^-22 kJ

Hence, crystal field splitting energy per mole = 3.95 * 10^-22 kJ * 6.023 * 10^23 mol^-1 = 238 kJ/mol

Part B: According to spectrochemical series, based on ligand strength, H2O is comparatively a strong field ligand than Cl-. Hence, replacing H2O with Cl-, the t2g electrons can easily excite to the eg level and thus decreases the value.

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