Reaction of $Br_2$ with $Na_2CO_3$ in aqueous solution gives sodium bromide and sodium bromate with evolution of $CO_2$ gas. The number of sodium bromide molecules involved in the balanced chemical equation is

$A_2O_x$ is oxidised to $AO_3^-$ by $MnO_4^-$ in acidic medium. If $1.5 \times 10^{-3} \text{ mole of } A_2O_x$ requires $40 \text{ mL}$ of $0.03 \text{ M } KMnO_4$ solution in acidic medium,which of the following statement$(s)$ is/are correct?

In which reaction is there a change in the oxidation state?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$I_2 + S_2O_3^{2-} \longrightarrow I^{-} + S_4O_6^{2-}$

Which among the following species acts as a self-indicator?

$5H_2O_2 + XClO_2 + 2OH^- \to XCl^- + YO_2 + 6H_2O$
In the above balanced reaction,the reaction is balanced when,