The number of electrons involved in the reduction of $Cr_2O_7^{2-}$ in acidic solution to $Cr^{3+}$ is

$MnO_4^- + C_2O_4^{2-} + H^+ \to Mn^{2+} + CO_2 + H_2O$ :
What are the correct stoichiometric coefficients for the balanced redox reaction?

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

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Ca(OH)_2 + SO_2 \longrightarrow CaSO_3 \downarrow + H_2O$

What is the result of the reaction between $KMnO_4$ and $HCl$?

Balance the following redox reactions using the oxidation number and ion-electron method:
$(1) H_2S + Fe^{3+} \to Fe^{2+} + S + H^{+}$
$(2) Cu + NO_3^{-} \to Cu^{2+} + NO_2$
$(3) Sn + NO_3^{-} + H^{+} \to Sn^{2+} + NH_4^{+} + H_2O$
$(4) As + NO_3^{-} + H^{+} \to AsO_4^{3-} + NO_2 + H_2O$