$3Br_2 + 6CO_3^{2-} + 3H_2O \to 5Br^- + BrO_3^- + 6HCO_3^-$
In the above reaction,

Nitrous acid was disproportionated to form water,$HNO_3$ and $X$. In another reaction,sodium nitrite was reacted with $H_2SO_4$ to form $NaHSO_4, HNO_3$,water and $Y$. What are $X$ and $Y$ respectively?

Given below are two statements :
Statement $I$: $S_8$ solid undergoes disproportionation reaction under alkaline conditions to form $S^{2-}$ and $S_2O_3^{2-}$.
Statement $II$: $ClO_4^{-}$ can undergo disproportionation reaction under acidic condition.
In the light of the above statements,choose the most appropriate answer from the options given below :

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$H_2O_2 \xrightarrow{R.T} H_2O + \frac{1}{2} O_2$

Auto-oxidation of bleaching powder gives:

Which anion can undergo both oxidation and reduction?