When chromite ore $\mathrm{FeCr}_2\mathrm{O}_4$ is fused with $\mathrm{NaOH}$ in presence of air, a yellow coloured compound(A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound(B) on reaction with $\mathrm{KCl}$ forms a orange coloured crystalline compound (C).(i) Write the formulae of the compounds (A), (B) and (C).(ii) Write one use of compound (C). ORComplete the following chemical equations:(i) $\mathrm{MnO}_4^{-}+3\mathrm{S}_2\mathrm{O}_3^{2-}+\mathrm{H}_2\mathrm{O}\rightarrow$ ?(ii) $\mathrm{Cr}_2\mathrm{O}_7^{2-}+3\mathrm{Sn}^{2+}+14\mathrm{H}^{+}\rightarrow$ ?