How many moles of $KMnO_4$ will be reduced by $1$ mole of $KI$ in an alkaline medium?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$CuSO_4 + Zn_{(s)} \longrightarrow ZnSO_4 + Cu$

What is the stoichiometric coefficient of the oxalate ion after balancing the following redox reaction?
$MnO_4^- + C_2O_4^{2-} + H^+ \rightarrow Mn^{2+} + CO_2 + H_2O$

Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$2NaBr + MnO_2 + 2H_2SO_4 \longrightarrow MnSO_4 + Na_2SO_4 + Br_2 + 2H_2O$

Consider the following reaction:
$xMnO_4^{-} + yC_2O_4^{2-} + zH^{+} \rightarrow xMn^{2+} + 2yCO_2 + \frac{z}{2}H_2O$
The values of $x, y$ and $z$ in the reaction are,respectively: