[આપેલ છે :પરમાણ્વીય દળ:-$Cr =52$ $amu$ અને $Cl =35\, amu ]$
\(=\frac{x \times 18}{(12+6 \times 16+35 \times 3+52)} \times 100=13.5\)
\(\Rightarrow \quad x=\frac{265 \times 13.5}{18 \times 100} \simeq 2\)
$(I)$ $\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Br}_{2}$
$(II)$ $ \mathrm{Na}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]$
$(III)$ $\mathrm{Na}_{3}\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\left(\Delta_{0}>\mathrm{P}\right)$
$(IV)$ $\left(\mathrm{Et}_{4} \mathrm{N}\right)_{2}\left[\mathrm{CoCl}_{4}\right]$