For the balanced equation $NO_2^- + H_2O \to NO_3^- + 2H^+ + ne^-$,the value of $n$ is .......

Complete the following reactions:
$(a) \ Cr_2O_7^{2-} + X \to 2CrO_4^{2-} + H_2O$
$(b) \ Cr_2O_7^{2-} + 14H^+ + X \to 2Cr^{3+} + 7H_2O$
$(c) \ 6I^- \to X + 6e^-$

Assign $A, B, C, D$ from the given type of reaction.
$2NaI + 2H_2SO_4 \,(Conc.) \longrightarrow Na_2SO_4 + I_2 + SO_2 + 2H_2O$

Calculate the equivalent weight of $KMnO_4$ in acidic,basic,and neutral media.

Write the balanced chemical equations for the following reactions:
$(1)$ Reaction between $MnO_4^-$ and $I^-$ in neutral or faintly alkaline solution.
$(2)$ Reaction between $MnO_4^-$ and $C_2O_4^{2-}$ in acidic medium $(H^+)$.

Identify the type of reaction for the following chemical equation: $CuO + H_2 \longrightarrow Cu + H_2O$