In the reaction of oxalate with permanganate in acidic medium,the number of electrons involved in producing one molecule of $CO_2$ is

Only $2 \ mL$ of $KMnO_4$ solution of unknown molarity is required to reach the end point of a titration of $20 \ mL$ of oxalic acid $(2 \ M)$ in acidic medium. The molarity of $KMnO_4$ solution should be . . . . . . . . . $M$.

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:

Observe the following stoichiometric equation:
$P_4 + 3 OH^{-} + 3 H_2 O \rightarrow PH_3 + 3 X^{-}$
What is the conjugate acid of $X^{-}$?

Consider the following equations:
$2 Fe^{2+} + H_2O_2 \rightarrow x A + y B$
(in basic medium)
$2 MnO_4^{-} + 6 H^{+} + 5 H_2O_2 \rightarrow x' C + y' D + z' E$
(in acidic medium)
The sum of the stoichiometric coefficients $x, y, x', y'$ and $z'$ for products $A, B, C, D$ and $E,$ respectively,is............

In the given half-reaction $Cr_2O_7^{2-} + ZH^{+} + e^- \to Cr^{3+} + H_2O$,find the value of $Z$.