Inorganic Chemistry
Since the iodide ion is a mild reducing agent, I − is easily oxidised to I2 by powerful oxidising agents such as chlorine:
- 2 KI(aq) + Cl2(aq) → 2 KCl + I2(aq)
This reaction is employed in the isolation of iodine from natural sources. Air will oxidize iodide, as evidenced by the observation of a purple extract when aged samples of KI are rinsed with dichloromethane. As formed under acidic conditions, hydroiodic acid (HI) is a stronger reducing agent.
Like other iodide salts, KI forms I3− when combined with elemental iodine.
- KI(aq) + I2(s) → KI3(aq)
Unlike I2, I3− salts can be highly water-soluble. Through this reaction, iodine is used in redox titrations. Aqueous KI3, "Lugol's solution," are used as disinfectants and as etchants for gold surfaces.
Potassium iodide is the precursor to silver(I) iodide, which is used for high speed photographic film:
- KI(aq) + AgNO3(aq) → AgI(s) + KNO3(aq)
Read more about this topic: Potassium Iodide, Structure, Production, Properties
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