Equivalent mass of ${\mathrm{Fe}}_3{\mathrm{O}}_4$ and ${\mathrm{Fe}}_2{\mathrm{O}}_3$ in the change ${\mathrm{Fe}}_3{\mathrm{O}}_4$ $⟶{\mathrm{Fe}}_2{\mathrm{O}}_3$ are

 (${\mathrm{M}}_1$ and ${\mathrm{M}}_2$ are molar mass of  ${\mathrm{Fe}}_3{\mathrm{O}}_4$ and ${\mathrm{Fe}}_2{\mathrm{O}}_3$, respectively.)

Find out how many moles of ${\mathrm{KMnO}}_4$ are needed to oxidise a mixture of $1 \mathrm{mole}$ each of ${\mathrm{FeSO}}_4, {\mathrm{FeC}}_2{\mathrm{O}}_4$ and ${\mathrm{Fe}}_2\left({\mathrm{C}}_2{\mathrm{O}}_4\right)$ completely in each medium?

The volume of $0.5 \mathrm{M} {\mathrm{H}}_2{\mathrm{SO}}_4$ required to dissolve $0.5 \mathrm{g}$ of copper $\left(\mathrm{II}\right)$ carbonate $\left({\mathrm{CuCO}}_3\right)$ is:

The equivalent weight of the metal, when $1.0 \mathrm{g}$ of metal nitrate gave $0.86 \mathrm{g}$ of metal sulphate is:

A mixture of ${\mathrm{Cu}}_2\mathrm{S}$ and $\mathrm{CuS}$ on oxidation by $\mathrm{Al}{\left({\mathrm{MnO}}_4\right)}_3$ in acidic medium gives ${\mathrm{Cu}}^{2+}$ and ${\mathrm{SO}}_2$. If molar masses of ${\mathrm{Cu}}_2\mathrm{S}, \mathrm{CuS}$ and $\mathrm{Al}{\left({\mathrm{MnO}}_4\right)}_3$ are ${\mathrm{M}}_1, {\mathrm{M}}_2$ and ${\mathrm{M}}_3$, respectively, then for this reaction which one are correct?