Which of the following has the maximum molar conductivity?

An aqueous solution of $CoCl_2$ on addition of excess of concentrated $HCl$ turns blue due to the formation of:

Aluminium trifluoride is insoluble in anhydrous $HF$ but dissolves on addition of $NaF$. Aluminium trifluoride precipitates out of the resulting solution when gaseous $BF_3$ is bubbled through. Give reasons.

Which of the following complexes is the most stable: $[Fe(H_2O)_6]^{3+}$,$[Fe(CN)_6]^{3-}$,$[Fe(C_2O_4)_3]^{3-}$,or $[FeCl_6]^{3-}$?

The molar ionic conductance of the octahedral complexes:
$(i)$ $PtCl_4 \cdot 5 NH_3$ $(ii)$ $PtCl_4 \cdot 4 NH_3$ $(iii)$ $PtCl_4 \cdot 3 NH_3$ $(iv)$ $PtCl_4 \cdot 2 NH_3$
Follow the order:

$HgCl_2$ is a covalent compound,sparingly soluble in water. The solubility increases by the addition of chloride ions due to: