Indicate the number of unpaired electrons in $K_3[Fe(CN)_6]$ and $K_4[Fe(CN)_6]$.

The octahedral complex $[Co(NH_3)_5SO_4]Cl$ exists in two isomeric forms $X$ and $Y$. Isomer $X$ reacts with $AgNO_3$ to give a white precipitate,but does not react with $BaCl_2$. Isomer $Y$ gives a white precipitate with $BaCl_2$ but does not react with $AgNO_3$. Isomers $X$ and $Y$ are $.....$

$A$ reaction of cobalt $(III)$ chloride and ethylenediamine in a $1:2$ mole ratio generates two isomeric products $A$ (violet coloured) and $B$ (green coloured). $A$ can show optical activity,but $B$ is optically inactive. What type of isomers do $A$ and $B$ represent?

Choose the complexes which are paramagnetic from the following:
$(i)$ $K_4[Fe(CN)_6]$
(ii) $K_3[Cr(CN)_6]$
(iii) $K_3[Fe(CN)_6]$
(iv) $K_2[Ni(CN)_4]$

Which of the following coordination compounds would exhibit optical isomerism?

Coordination isomerism is formed by the interchange of ligands between which of the following?