Chemistry - Chemical Equilibrium Question with Solution | TestHub

${\mathrm{Fe}}_{\mathrm{aq}}^{+3}+{\mathrm{SCN}}_{\mathrm{aq}}^{-}\rightleftharpoons [\mathrm{Fe}(\mathrm{SCN}){]}_{\mathrm{aq}}^{+2}$

yellow deep red

$F{e}^{+3}+N{a}_2{C}_2{O}_4\to {\left[Fe{\left(C_2{O}_4\right)}_3\right]}_{aq}^{-3}\dots \left(1\right)$

light green

$HgC{l}_2+SC{N}^{-}\to \underset{\text{ colourless solution }}{{\left[\mathrm{Hg}(\mathrm{SCN}{)}_4\right]}^{-2}}.\dots \dots \left(2\right)$

Due to the reaction of ${\mathrm{Na}}_2{\mathrm{C}}_2{\mathrm{O}}_4$ or ${\mathrm{Hg}}_{(\mathrm{aq})}^{+2}$; the conc. of ${\mathrm{Fe}}^{+3}$ or ${\mathrm{SCN}}^{-}$decreases. So, equilibrium reaction should shift backward, that will reduce the deep red colour of the solution