1.

Consider the following list of reagents : Acidified K_(2)Cr_(2)O_(7), alkaline KMnO_(4), CuSO_(4), H_(2)O_(2),Cl_(2),O_(3),FeCl_(3),HNO_(3) and Na_(2)S_(2)O_(3). The total number of reagents that can oxidise aqueous iodide to iodine is

Answer»


Solution :`I^(-)` to `I_(2)` oxidation can be done by acidified `K_(2)Cr_(2)O_(7), CuSO_(4),H_(2)O_(2)`
`K_(2)Cr_(2)O_(7)+KI+H_(2)SO_(4)rarrK_(2)SO_(4)+Cr_(2)(SO_(4))_(3)+I_(2)+H_(2)O`
`2CuSO_(4)+4KIrarr 2CuI darr+I_(2)+2K_(2)SO_(4)`
`H_(2)O_(2)+2KIrarr2KOH+I_(2)`
`H_(2)O+2KI+O_(3)rarr 2KOH+O_(2)+I_(2)`
`FeCl_(3)+2KIrarr2KCl+FeCl_(2)+I_(2)`
`HNO_(3)+KIrarr KNO_(3)+I_(2)+NOuarr`
`Na_(2)S_(2)O_(3)+KI rarr "no reaction."`
Note : In `H_(2)O_(2) and O_(3),I^(-)` to `tI_(2)` oxidation will occur initially. However as concentration of KOH builds up, it will begin causing disproportionation of resulting `I_(2)` to `IO_(3)^(-)`.


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