The brown ring test for $NO_2^-$ and $NO_3^-$ ions is due to the formation of which of the following complex ions?

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:

$A$ pink coloured aqueous solution of $Co(NO_3)_2$ turns blue on the addition of $HCl$ gradually. This colour change happens due to the formation of

$CuSO_4$ decolourises on addition of $KCN$,the product is

Which of the following gives the maximum number of ions in aqueous solution?

$A$ solution contains $2.675 \ g$ of $CoCl_3 \cdot 6NH_3$ $(M = 267.5 \ g/mol)$. When passed through a cation exchanger,the chloride ions liberated are treated with excess $AgNO_3$ to yield $4.78 \ g$ of $AgCl$ $(M = 143.5 \ g/mol)$. What is the formula of the coordination compound?