In which case is a racemic mixture obtained upon mixing its mirror images ($d$ and $l$ forms) in a $1:1$ molar ratio?

Which of the following compounds is paramagnetic and colored?

An octahedral complex having molecular composition $Co \cdot 5NH_3 \cdot Cl \cdot SO_4$ has two isomers $A$ and $B$. The solution of $A$ gives a white precipitate with $AgNO_3$ solution and the solution of $B$ gives a white precipitate with $BaCl_2$ solution. The type of isomerism exhibited by the complex is,

$[Fe(NO_{2})_{3} Cl_{3}]$ and $[Fe(ONO)_{3} Cl_{3}]$ show

Which of the following isomerism is exhibited by $[CrCl_2(OH)_2(NH_3)_2]^-$?

Aqueous solution of $Ni^{2+}$ contains $[Ni(H_2O)_6]^{2+}$ and its magnetic moment is $2.83 \, BM$. When ammonia is added to it,comment on the magnetic moment of the solution.