Total number of reagents give below reacted with `KI_((aq))` to produce `I_(2):`
`CuSO_(4)" "Hg(NO_(3))_(2)`
`"Concentrate"H_(2)SO_(4)"Concentrate"H_(3)PO_(4)`
`KMnO_(4)//H^(+)" "K_(2)Cr_(2)O_(7)//H^(+)`
`Cl_(2)` water acidify bleaching powder
`Pb(NO_(3))_(2)NaNo_(2)+HCl("dil.")`

Answer

3

Explanation

`I^(-)` ions are oxidised to `I_(2)` on reacting with an oxidising agent. The oxidising agents among the following are :
`2Cu^(2+)+4I^(-) to Cu_(2)I_(2)+I_(2)`
`{:(2MnO_(4)^(-)+16H^(+)+10I^(-)),(" "darr),(2Mn^(2+)+5I_(2)+8H_(2)O),(Cr_(2)O_(7)^(2-)+14H^(+)+6I^(-)),(" "darr),(overset(3+)(2Cr)+7H_(2)O+3I_(2)):}`