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1. The ligand splitting for aqueous octahedral complexes of Co 2+ and Co 3+ are

ID: 795368 • Letter: 1

Question

1.      The ligand splitting for aqueous octahedral complexes of  Co2+  and Co3+ are 8400 cm-1 and 16750 cm-1, and the electron pairing energy is approx.  22000 cm-1 for both complexes.  Determine the ligand field stabilization energy and  magnetic moment for  both complexes.  Then explain which complex is stable in aqueous solution.

The ligand splitting for aqueous octahedral complexes of Co2+ and Co3+ are 8400 cm-1 and 16750 cm-1, and the electron pairing energy is approx. 22000 cm-1 for both complexes. Determine the ligand field stabilization energy and magnetic moment for both complexes. Then explain which complex is stable in aqueous solution.

Explanation / Answer

unpaired electrons in Co2+ = 5, and Co3+ = 6

MM of Co2+ = sqrt(n(n+2)) = sqrt(5*7) = 5.92 and that of Co3+ = 6.93 BM

LFSE of Co2+ = 0, and that of Co3+ = -3/5*16750 = -10050 cm^-1

So, Co3+ is more stable because of less LFSE.