NEET Solved Paper 2014 Question 27
Question: Among the following complexes, the one which shows zero crystal field stabilisation energy (CFSE) is [AIPMT 2014]
Options:
A) $ {{[Mn{{(H _2O)}_6}]}^{3+}} $
B) $ {{[Fe{{(H _2O)}_6}]}^{3+}} $
C) $ {{[Co{{(H _2O)}_6}]}^{2+}}, $
D) $ {{[Co{{(H _2O)}_6}]}^{3+}} $
Show Answer
Answer:
Correct Answer: B
Solution:
The CFSE for octahedral complex is given by
$ CFSE=[-0.4t _{2g}{e^{-}}+0.6e _{g}{e^{-}}] $ For $ M{n^{3+}}[3d^{4}]\to \ t_2g^{3}\ e_g^{1} $
$ \therefore $ $ CFSE=[-0.4,\times 3+0.6\times 1] $ = 0.6 For $ F{e^{3+}}[3d^{5}]\to t_2g^{3}e_g^{2} $
$ CFSE=[-(0.4\times 3)+(0.6\times 2)]=0 $ For $ C{o^{2+}}[3d^{7}]\to t_2g^{5}e_g^{2} $
$ CFSE=[(-0.4\times 5)+(2\times 0.6)]=-0.8 $ For $ C{o^{3+}}[3d^{6}]\to t_2g^{4}e_g^{2} $
$ CFSE=[(-0.4\times 4)+(2\times 0.6)]=-0.4 $
