Iodine is obtained commercially from Chile saltpetre through the reaction

Options

A. `2KI+Cl_(2)rarrI_(2)+2KCl`
B. `IO^(-)+5I^(-)+6H^(+)rarr3I_(2)+3H_(2)O`
C. `2IO_(3)^(-)+5HSO_(3)^(-)rarr3HSO_(4)^(-)+2SO_(4)^(2-)+H_(2)O+I_(2)`
D. `2I^(-)+H_(2)O_(2)rarrI_(2)+2OH^(-)`

Answer

3

Explanation

There are two different commericial method of obtaining iodine. The methods used depends on whether the source is chile saptpeter or natural brine. Iodine is manufactured from natural brines (or sea weed) by the oxidation of iodide ion with chlorine.
Chile sltpeter is mainly `NaNO_(3)`, but it contain traces of sodium iodate `(NaIO_(3))` and sodium periodate `(NaIO_(4))` . Pure `NaNO_(3)` is obtianed by dissolving saltpeter in water and crystallizing `NaNO_(3)`. Thus the iodate residues accumulate and concentrated in the mother liquor. Eventually, this concentrate is divided into two parts. One parts is reduced with `NaHSO_(3)` to give `I^(-)`. This is mixed with the unreacted part, which is filtered off as a solid and then purified by sublimation:
` 2IO_(3)^(-)+6HSO_(3)^(-)rarr2I^(-)+6SO_(4)^(2-)+6H^(+)`
`5I^(-)+IO_(3)^(-)+6H^(+)rarr3I_(2)+3H_(2)O`
`NaIO_(3)(aq.)+3NaHSO_(3)(aq.)rarrNal(aq.)+3NaHSO_(4)(aq.)`
`NaIO_(3)(aq.)+5NaI(aq.)+3H_(2)SO_(4)(aq.)rarr3I_(2)(s)+3H_(2)O(l)+3Na_(2)SO_(4)(aq.)`