JEE MAIN - Chemistry (2021 - 26th August Evening Shift - No. 8)
Arrange the following Cobalt complexes in the order of increasing Crystal Field Stabilization Energy (CFSE) value.
Complexes : $$\mathop {{{[Co{F_6}]}^{3 - }}}\limits_A ,\mathop {{{[Co{{({H_2}O)}_6}]}^{2 + }}}\limits_B ,\mathop {{{[Co{{(N{H_3})}_6}]}^{3 + }}}\limits_C and \mathop {{{[Co{{({en})}_3}]}^{3 + }}}\limits_D $$
Choose the correct option :
Complexes : $$\mathop {{{[Co{F_6}]}^{3 - }}}\limits_A ,\mathop {{{[Co{{({H_2}O)}_6}]}^{2 + }}}\limits_B ,\mathop {{{[Co{{(N{H_3})}_6}]}^{3 + }}}\limits_C and \mathop {{{[Co{{({en})}_3}]}^{3 + }}}\limits_D $$
Choose the correct option :
A < B < C < D
B < A < C < D
B < C < D < A
C < D < B < A
Explanation
(i) CFSE $$\propto$$ charge or oxidation no. of central metal ion.
(ii) CFSE $$\propto$$ strength of ligand
en > NH3 > H2O > F$$-$$
$$\therefore$$ order of CFSE
$$\mathop {{{[Co{{(en)}_3}]}^{ + 3}}}\limits^{III} > \mathop {{{[Co{{(N{H_3})}_6}]}^{ + 3}}}\limits^{III} > \mathop {{{[Co{F_6}]}^{ - 3}}}\limits^{III} > \mathop {{{[Co{{({H_2}O)}_6}]}^{ + 2}}}\limits^{III} $$
(ii) CFSE $$\propto$$ strength of ligand
en > NH3 > H2O > F$$-$$
$$\therefore$$ order of CFSE
$$\mathop {{{[Co{{(en)}_3}]}^{ + 3}}}\limits^{III} > \mathop {{{[Co{{(N{H_3})}_6}]}^{ + 3}}}\limits^{III} > \mathop {{{[Co{F_6}]}^{ - 3}}}\limits^{III} > \mathop {{{[Co{{({H_2}O)}_6}]}^{ + 2}}}\limits^{III} $$
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