Question

Chlorine reacts with water according to the equation: `Cl_2 + H_2O -> HCIO + H^+ + Cl^-`. Given this, how do you write an equation to show how iodine reacts with water?

Answer 1

See explanation.

Explanation:

Iodine is strongly reactive, even though it is less extreme for iodine than for other halogens. Iodine cannot be found as an element, but rather as`I_2` molecules, as `I^-` ions, or as iodate (a salt of iodinic acid with `IO_3^-` anion).

When iodine is added to water, the following reaction results:

`I_2(l) + H_2O(l) -> OI^(-)(aq) + 2H^+(aq) + I^(-)(aq)`

`I_2` molecules and water molecules react to substances such as hypoiodite `"OI"^(-)`. The reaction can move both ways of the equilibrium, depending on the pH of the solution.

Iodine may also occur as

`I_3^(-)(aq), HIO(aq), IO^(-)(aq), HIO_3(aq)`

Iodine can bind to many different substances, for example, other halogens. The compounds that are formed behave differently when they come in contact with water.

Solubility of iodine and iodine compounds

Water solubility of iodine is determined by temperature `(20^@C)` and pressure `("1 bar")`, and is relatively low. Iodine is better soluble in iodine solutions. The following reaction mechanism occurs:

`I_2 + I^-) -> [I_3]^-`