Identify the correct statements about the following stoichiometric equation.
$aP_4 + bOH^{-} + cH_2O \longrightarrow dPH_3 + eH_2PO_2^{-}$
$I$. $a+b+c=5$
$II$. $b+c-e=3$
$III$. The oxidation state of $P$ in $H_2PO_2^{-}$ is $+1$.

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

For the reaction $3K_2MnO_4 + 2H_2SO_4 \rightarrow 2KMnO_4 + K_2SO_4 + MnO_2 + 2H_2O$,what is the stoichiometric ratio of the reactants $K_2MnO_4$ to $H_2SO_4$?

When thiosulphate ion is oxidised by iodine,which one of the following ions is produced?

Given the redox reaction:
$X Na_2HAsO_3 + Y NaBrO_3 + Z HCl \longrightarrow NaBr + H_3AsO_4 + NaCl$
The values of $X$,$Y$,and $Z$ in the balanced equation are respectively:

For the following balanced equation,$a, b, c$ and $d$ will be respectively:
$IO_3^- + aI^- + bH^+ \to cH_2O + dI_2$