$2 IO_3^- + x I^- + 12 H^+ \rightarrow 6 I_2 + 6 H_2 O$. What is the value of $x$?

Assign $A, B, C, D$ from the given type of reaction.
$3Mg_{(s)} + N_{2(g)} \longrightarrow Mg_3N_{2(s)}$

Balance the following redox reactions by the ion-electron method:
$(a)$ $MnO_4^-(aq) + I^{-}(aq) \rightarrow MnO_2(s) + I_2(s)$ (in basic medium)
$(b)$ $MnO_4^-(aq) + SO_2(g) \rightarrow Mn^{2+}(aq) + HSO_4^-(aq)$ (in acidic solution)
$(c)$ $H_2O_2(aq) + Fe^{2+}(aq) \rightarrow Fe^{3+}(aq) + H_2O(l)$ (in acidic solution)
$(d)$ $Cr_2O_7^{2-} + SO_2(g) \rightarrow Cr^{3+}(aq) + SO_4^{2-}(aq)$ (in acidic solution)

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

$A_2O_x$ 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?

Write the balanced chemical equations for the following reactions:
$(1)$ Reaction of $Cr_2O_7^{2-}$ with $Fe^{2+}$ in acidic medium.
$(2)$ Reaction of $MnO_4^-$ with $Fe^{2+}$ in acidic medium.