Question

(a) How is Ozonised oxygen prepared in the laboratory? Give reason.
(b) Give the composition of "Oleum".

Answer 1

(a) A slow dry stream of oxygen is passed through a silent electrical discharge. Oxygen is converted to ozone. The product is known as ozonized oxygen. It contains about 10% ozone. If more than 10% of ozone is required, a battery of ozonisers is used in which pure ozone is condensed in a container surrounded by liquid oxygen. In place of silent electrical discharge, one can also use ultraviolet radiations. Conversion of oxygen to ozone is endothermic process. Use of a silent electrical discharge prevents decomposition. Ozone is explosive and highly reactive.
$3O_2\to 2O_3$
(b) "Oleum" is fuming sulphuric acid. Its composition is $H_2{S}_2{O}_7$.
$H_{2}S{O}_4+S{O}_3\to H_2{S}_2{O}_7$