The total number of possible isomers of the complex compound $[Cu(NH_3)_4] [PtCl_4]$ is:

Ordinary light is converted into plane-polarized light with the help of which of the following?

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.

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

Total number of unpaired electrons in the complex ions $[Co(NH_3)_6]^{3+}$ and $[NiCl_4]^{2-}$ is...............

The magnetic moment of $[CoF_6]^{3-}$ as per spin only formula (in $BM$) is