(show all your works and make sure that you do all questions from part a to part
ID: 1017190 • Letter: #
Question
(show all your works and make sure that you do all questions from part a to part e. Sorry for long questions, but I give thanks to anyone who help me answer all questions below from part a to part e)
a. complete the following table for each octahedral complex ion listed:
using the results from the above table:
b. write a relative spectrochemical series for the ligands in the chromium complexes above
compound wavelength of maximum absorption(nm) Splitting(kJ/mol) Splitting(kJ/photon) [Co(NH3)6]3+ 405 [CrCl6]3- 735 [Cr(CN)6]3- 381 [Cr(H2O)6]3+ 562 [Cr(NH3)6]3+ 462 [Fe(H2O)6]2+ 966 [Fe(H2O)6]3+ 730 [Ir(NH3)6]3+ 244 [Rh(NH3)6]3+ 295Explanation / Answer
a. Table
dE (kJ/photon) = hc/l
h = planck's constant
c = speed of light
l = wavelength
dE (kJ/mol) = dE (kJ/photon) x avogadro's number
compound wavelength (nm) dE splitting dE splitting
(kJ/mol) (kJ/photon)
[Co(NH3)6]3+ 405 2.95 x 10^5 4.91 x 10^-19
[CrCl6]3- 735 1.63 x 10^5 2.70 x 10^-19
[Cr(CN)6]3- 381 3.14 x 10^5 5.22 x 10^-19
[Cr(H2O)6]3+ 562 2.13 x 10^5 3.54 x 10^-19
[Cr(NH3)6]3+ 462 2.59 x 10^5 4.30 x 10^-19
[Fe(H2O)]2+ 966 1.23 x 10^5 2.06 x 10^-19
[Fe(H2O)]3+ 730 1.64 x 10^5 2.72 x 10^-19
[Ir(NH3)6]3+ 244 4.90 x 10^5 8.14 x 10^-19
[Rh(NH3)6]3+ 295 4.05 x 10^5 6.74 x 10^-19
b. Spectrochemical series (ligands) for Cr complex energy (kJ/mol) in increasing order : Cl- < H2O < NH3 < CN-
c. As the oxidation state increases for Fe from +2 to +3 the energy (kJ/mol) for splitting also increases.
d. As we go down the group from Co to Rh to Ir the splitting energy (kJ/mol) also increases accordingly.
e. with dE = 2.74 x 10^-19 J
Wavelength = hc/dE = 6.626 x 10^-34 x 3 x 10^8/2.74 x 10^-19= 7.25 x 10^-7 m = 725 nm
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