In acid solution,the reaction $MnO_4^- \to Mn^{2+}$ involves

In the reactions given below,identify the species undergoing oxidation and reduction:
$(i)$ $H_{2}S_{(g)} + Cl_{2(g)} \rightarrow 2HCl_{(g)} + S_{(s)}$
$(ii)$ $3Fe_{3}O_{4(s)} + 8Al_{(s)} \rightarrow 9Fe_{(s)} + 4Al_{2}O_{3(s)}$
$(iii)$ $2Na_{(s)} + H_{2(g)} \rightarrow 2NaH_{(s)}$

Identify the correct statement for the following reaction:
$3 \ Mg + N_2 \longrightarrow Mg_3N_2$

Observe the following reaction:
$2 KClO_{3(s)} \xrightarrow{\Delta} 2 KCl_{(s)} + 3 O_{2(g)}$
In this reaction:

Addition of iron filings to $CuSO_4$ solution causes the precipitation of $Cu$ due to the:

What is a reduction reaction? Give its examples.