Explanation

(b)
In $\lbrack Co(en)_{2}{Cl}_{2}\rbrack$, four isomers are possible, two geometrical isomers and two optical isomers.
[image:9_image287.emf]
Now, cis-isomer also show optical isomerism. Cis isomer exists in enantiomeric form as it is unsymmetrical.
Plane mirror
[image:9_image288.emf]