Iodine - ₅₃I: reactions of 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