$A$ few drops of $KMnO_4$ solution are added to an acidic solution containing an anion. Which of the following,if present,will $NOT$ cause a change in the color of the $KMnO_4$ solution?

$X + H_2SO_4 \to Y$ (colorless gas) and $Y + K_2Cr_2O_7 + H_2SO_4 \to$ green solution. Then $X$ and $Y$ are respectively ........

In the reaction of sulphur with concentrated sulphuric acid,the oxidised product is $X$ and the reduced product is $Y$. $X$ and $Y$ are respectively:

Assign $A, B, C, D$ from the given type of reaction.
$KMnO_4 + NaNO_3 \longrightarrow$ No reaction

The colour of an iodine solution is discharged by shaking it with an aqueous solution of:

Balance the following redox reactions using the oxidation number and ion-electron method:
$(1) \ Zn + NO_3^- + H^+ \to Zn^{2+} + N_2O + H_2O$
$(2) \ I^- + O_2 + H_2O \to I_2 + OH^-$
$(3) \ MnO_4^- + C_2H_5OH \to Mn^{2+} + CH_3COOH$