When $H_2S$ is passed through acidified $KMnO_4,$ we get

In the balanced chemical reaction,$IO_3^- + a\;I^{-} + b\;H^{+} \to c\;H_2O + d\;I_2$,$a$,$b$,$c$,and $d$ respectively correspond to

Which of the following reagents causes the aqueous colored solution of acidic $KMnO_4$ to become colorless?

For the balanced redox reaction $aZn + b \, HNO_3 \to c \, Zn(NO_3)_2 + d \, NH_4NO_3 + 3H_2O$,the value of $b$ 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 . . . . . . . . . $M$.

Phenolphthalein does not act as an indicator for the titration between