Chemical reactions of the elements
Reaction of iodine with air
Iodine, I2 is not reactive towards with oxygen, O2, or nitrogen, N2. However, iodine does react with ozone, O3, the second allotrope of oxygen, to form the unstable yellow I4O9, the nature of which is perhaps I(IO3)3.
Reaction of iodine with water
Iodine, I2, reacts with water to produce hypoiodite, OI-. The position of the equilibrium depends very much upon the pH of the solution.
I2(l) + H2O(l) ⇌ OI-(aq) + 2H+(aq) + I-(aq)
Reaction of iodine with the halogens
Iodine, I2, reacts with fluorine, F2, at room temperature to form the pentafluoride iodine(V) fluoride. At 250°C the same reaction affords the heptafluoride iodine(VII) fluoride. With careful control of the reaction conditions, (-45°C, suspension in CFCl3), it is posible to isolate the trifluoride iodine(III) fluoride.
I2(s) + 5F2(g) → 2IF5(l) [colourless]
I2(g) + 7F2(g) → 2IF7(g) [colourless]
I2(s) + 3F2(g) → 2IF3(s) [yellow]
Iodine, I2, reacts with bromine, Br2, form the very unstable, low melting solid, interhalogen species iodine(I) bromide.
I2(s) + Br2(l) → 2IBr(s)
Iodine reacts with chlorine at -80°C with excess liquid chlorine to form "iodine trichloride", iodine (III) chloride, actually I2Cl6. Iodine reacts with chlorine in the presence of water to form iodic acid.
I2(s) + 3Cl2(l) + I2Cl6(s) [yellow]
I2(s) + 6H2O(l) + 5Cl2(g) → 2HIO3(s) + 10HCl(g)
Reaction of iodine with acids
Iodine reacts with hot concentrated nitric acid to form iodic acid. The iodic acid crystallizes out on cooling
3I2(s) + 10HNO3(aq) → 6HIO3(s) + 10NO(g) + 2H2O(l)
Reaction of iodine with bases
Iodine, I2, reacts with hot aqueous alkali to produce iodate, IO3-. Only one sixth of the total iodine is converted in this reaction.
3I2(g) + 6OH-(aq) → IO3-(aq) + 5I-(aq) + 3H2O