Question

How is O₃ estimated quantitatively?

Answer 1

Quantitatively, ozone can be estimated with the help of potassium iodide. When ozone is made to react with potassium iodide solution buffered with a borate buffer (pH 9.2), iodine is liberated. This liberated iodine can be titrated against a standard solution of sodium thiosulphate using starch as an indicator. The reactions involved in the process are given below.

`2I^(-)   + H_2O + O_3 ->  2OH^(-) + I_2 + O_2`

Iodide                Ozone                     Iodine

 

`I_2     +     2Na_2S_2O_3      ->         Na_2S_4O_6  + 2 Nal`

            Sodium thiosulphate          Sodium tetrathionate