Consider the following list of reagents, Acidified  ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$, alkaline${\mathrm{KMnO}}_4, {\mathrm{CuSO}}_4, {\mathrm{H}}_2{\mathrm{O}}_{2,} {\mathrm{Cl}}_2, {\mathrm{O}}_3,$  ${\mathrm{FeCl}}_3, {\mathrm{HNO}}_3 \mathrm{and} {\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3.$
The total number of reagents that can oxidize aqueous iodide to iodine is ------------

KEY = 7
$\left(\mathrm{i}\right) {\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7 + 7{\mathrm{H}}_2{\mathrm{SO}}_4 + 6\mathrm{KI} \to 4{\mathrm{K}}_2{\mathrm{SO}}_4 + {\mathrm{Cr}}_2 {\left({\mathrm{SO}}_4\right)}_3 + 3{\mathrm{I}}_2 + 7{\mathrm{H}}_2\mathrm{O}$ 
$\left(\mathrm{ii}\right) 2{\mathrm{CuSO}}_4 + \mathrm{KI} \to {\mathrm{Cu}}_2{\mathrm{I}}_2 + {\mathrm{I}}_2 + 2{\mathrm{K}}_2{\mathrm{SO}}_4$
$\left(\mathrm{iii}\right) 2\mathrm{KI} + {\mathrm{H}}_2{\mathrm{O}}_2 \to 2\mathrm{KOH} + {\mathrm{I}}_2$
$\left(\mathrm{iv}\right) 2\mathrm{KI} + {\mathrm{Cl}}_2 \to 2\mathrm{KCl} + {\mathrm{I}}_2$
$\left(\mathrm{v}\right) 2\mathrm{KI} + {\mathrm{O}}_3 + {\mathrm{H}}_2\mathrm{O}\to 2\mathrm{KOH} + {\mathrm{I}}_2 + {\mathrm{O}}_2$
$\left(\mathrm{vi}\right) 2{\mathrm{FeCl}}_3 + 2\mathrm{KI}\to 2{\mathrm{FeCl}}_2 + {\mathrm{I}}_2 + 2\mathrm{KCl}$
$\left(\mathrm{vii}\right) 8{\mathrm{HNO}}_3 + 6\mathrm{KI}\to 6{\mathrm{KNO}}_3 + 2\mathrm{NO} + 4{\mathrm{H}}_2\mathrm{O} + 3{\mathrm{I}}_2$
$\left(\mathrm{viii}\right) 2{\mathrm{KMnO}}_4 + \mathrm{KI} + {\mathrm{H}}_2\mathrm{O}\to {\mathrm{KIO}}_3 + 2{\mathrm{MnO}}_2 + 2\mathrm{KOH}$
$\left(\mathrm{ix}\right) {\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3 \mathrm{will} \mathrm{not} \mathrm{react} \mathrm{with} \mathrm{KI}$