In the reaction $Zn + 2H^{+} + 2Cl^{-} \to Zn^{2+} + 2Cl^{-} + H_2$,the spectator ion is

$KMnO_4$ acts as an oxidising agent in acidic medium. The number of moles of $KMnO_4$ that will be needed to react with one mole of sulphide ion $(S^{2-})$ in acidic solution is . . . . . . (in $/5$)?

Write the balanced chemical equation for the following reaction:
$Cl_2O_7$ in the gaseous state combines with an aqueous solution of hydrogen peroxide $(H_2O_2)$ in an acidic medium to give chlorite ion $(ClO_2^-)$ and oxygen gas $(O_2)$. (Balance by the ion-electron method)

Assign $A, B, C, D$ from the given type of reaction.
$Na_2CO_3 + PbSO_4 \longrightarrow PbCO_3 \downarrow + Na_2SO_4$

How many moles of $KMnO_4$ are required to oxidize $1 \ mol$ of $Fe(C_2O_4)$ in an acidic medium?

What is the number of electrons gained by $Cl$ atom when $n$ mole of $ClO_4^-$ is transformed into $n$ mole of $ClO_2^-$ ion?