$1 \mathrm{mol}$ of iron $\left(\mathrm{Fe}\right)$ reacts completely with $0.65 {\mathrm{molO}}_2$ to give a mixture of only $\mathrm{FeO}$ and ${\mathrm{Fe}}_2{\mathrm{O}}_3.$ Mole ratio of ferrous oxide to ferric oxide is :-

$28{\mathrm{NO}}_3^{-}+3{\mathrm{As}}_2{ \mathrm{S}}_3+4{\mathrm{H}}_2\mathrm{O}\to 6{\mathrm{AsO}}_4{}^{3-}+28\mathrm{NO}+9{\mathrm{SO}}_4{}^{2-}+{\mathrm{H}}^{+}$

What will be the equivalent mass of ${\mathrm{As}}_2{\mathrm{S}}_3$ in above reaction

When arsenic sulphide is boiled with $\mathrm{NaOH}$, sodium arsenite and sodium thioarsenite are formed according to reaction:

${\mathrm{xAs}}_2{\mathrm{S}}_3+\mathrm{yNaOH}⟶{\mathrm{xNa}}_3{\mathrm{AsO}}_3+{\mathrm{xNa}}_3{\mathrm{AsS}}_3+\frac{\mathrm{y}}{2}{\mathrm{H}}_2\mathrm{O}$

What are the values of $\mathrm{x}$ and $\mathrm{y}$?

$0.10 \mathrm{g}$ of a sample containing ${\mathrm{CuCO}}_3$ and some inert impurity was dissolved in dilute sulphuric acid and volume made up to $50 \mathrm{mL}.$ This solution was added into $50 \mathrm{mL}$ of $0.04 \mathrm{MKI}$ solution where copper precipitates as $\mathrm{CuI}$ and ${\mathrm{I}}^{-}$is oxidized into ${\mathrm{I}}_3^{-}.$ A $10 \mathrm{mL}$ portion of this solution is taken for analysis, filtered and made up free ${\mathrm{I}}_3^{-}$ and then treated with excess of acidic permanganate solution. Liberated iodine required $20 \mathrm{mL}$ of $2.5 \mathrm{mM}$ sodium thiosulphate solution to reach the end point.

Determine weight percentage of ${\mathrm{CuCO}}_3$ in the original sample,