Question

The complex ion [Co(OH2)6](3+) is blue in an aqueous solution. Estimate the crystal field splitting energy (in kJ/mol) for this ion. The complex ion [Co(OH2)6](3+) is blue in an aqueous solution. Estimate the crystal field splitting energy (in kJ/mol) for this ion.

127 kJ/mol

328 kJ/mol

302 kJ/mol

282 kJ/mol

199 kJ/mol

Answer 1

E = (h X c) / lambda

where h = plancks constant = 6.626 X 10^-34 j s
c = velocity of light = 3 X 10^8 m/s
lambda = wavelength = Blue colour = 450-495 nm

Here I am taking 470 is an averate wave lengnth = 470 X 10-9 m

so E = ( 6.626 X 10^-34 X 3 X 10^8) / 470 X 10^-9

E = 1.988 X 10^-25 / 470 X 10^-9

E = 4.20 X 10^-19 j

so for 1 ion .....energy is 4.20 X 10^-19 j

so for 6.022 X 10^23 ions ( 1 mole) ...energy is 4.20 X 10^-19 X 6.022 X 10^23 = 25.582 X 10^4 j/mole

in order to get the value in kj/mole divide it by 1000...

25.582 X 10^4/1000 = 255.82 kj/mole

So answer similar to 282 KJ/Mol

Because Blue wavelengh I have taken average 470 nm.