What is the value of $n$-factor of $[Fe(CN)_6]^{-4}$ in the given reaction?
$[Fe(CN)_6]^{-4} \xrightarrow{MnO_4^-/H^{+}} Fe^{+3} + CO_2 + NO_3^-$

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

When sulphur dioxide is passed in an acidified $K_{2}Cr_{2}O_{7}$ solution,the oxidation state of sulphur is changed from

Assign $A, B, C, D$ from the given type of reaction.
$3PbS + 8HNO_3 \text{ (dil.)} \longrightarrow 3Pb(NO_3)_2 + 3S \downarrow + 2NO + 4H_2O$

Which of the following reactions of $KMnO_4$ occurs in acidic medium?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Pb_3O_4 + 8HCl \xrightarrow{\text{Warm}} 3PbCl_2 + Cl_2 + 4H_2O$