How many moles of electrons are required to reduce $2.5 \ mol$ of $Cr_2O_7^{2-}$ to $Cr^{3+}$?

After balancing the equation,$C_2O_4^{2-} + H^+ + MnO_4^- \longrightarrow CO_2 + Mn^{2+} + H_2O$,the coefficient of $CO_2$ is:

$KMnO_4$ acts as an oxidising agent in acidic medium. The number of moles of $KMnO_4$ that will be needed to react with one mole of sulphide ion $(S^{2-})$ in acidic solution is . . . . . . (in $/5$)?

$6 Fe_3O_4 + 2 MnO_4^- + H_2O \to 9 Fe_2O_3 + 2 MnO_2 + 2 OH^-$ Calculate the equivalent weight of $Fe_3O_4$ in the above equation.

The number of moles of $KMnO_4$ reduced by one mole of $KI$ in alkaline medium is:

Assign $A, B, C, D$ from the given type of reaction.
$Ba(OH)_2 + SO_2 \longrightarrow BaSO_3 \downarrow + H_2O$