In ${K_4}[Fe(CN)_6]$,$Fe$ is in the form of

Consider the following complexes:
$(a) K_2PtCl_6$
$(b) PtCl_4 \cdot 2NH_3$
$(c) PtCl_4 \cdot 3NH_3$
$(d) PtCl_4 \cdot 5NH_3$
Their electrical conductances in aqueous solutions are:

Which complex absorbs the wavelength of red light?

Which of the following complexes has the highest stability at $298 \ K$?

The yellow compound $PbCrO_4$ dissolves upon treatment with a hot $NaOH$ solution. The lead-containing product formed is a:

The $IR$ stretching frequencies of free $CO$ and $CO$ in $[V(CO)_6]^-$,$[Cr(CO)_6]$ and $[Mn(CO)_6]^+$ are $2143 \, cm^{-1}$,$1860 \, cm^{-1}$,$2000 \, cm^{-1}$ and $2090 \, cm^{-1}$,respectively. Then the correct statement about metal carbonyls is: