Question

The $CFSE$ for $\left]\right(CoCl{)}_6{]}^{4-}$ complex is $18000c{m}^{-1}$. The $△$ for $[CoC{l}_4{]}^{2-}$ will be

• A. $18000c{m}^{-1}$
• B. $16000c{m}^{-1}$
• C. $8000c{m}^{-1}$
• D. $2000c{m}^{-1}$

Answer 1

Answer: (C)

$8000c{m}^{-1}$

$\left[\right(CoC{l}_6{]}^{4-}$ and $[CoC{l}_4{]}^{2-}$ have octahedral and tetrahedral geometries respectively.

For $\left[\right(CoC{l}_6{]}^{4-}$, the CFSE ${\Delta }_o=18000c{m}^{-1}$.

The relationship between the crystal field stabilization energies for octahedral and tetrahedral field is ${\Delta }_t=\frac{4}{9}{\Delta }_o$.

Substitute value in the above expression.
$[CoC{l}_4{]}^{2-}=\frac{4}{9}\times 18000c{m}^{-1}=8000c{m}^{-1}$.