In the presence of water, sulphur is oxidized by ozone to yield

The presence of sulphur in gun powder

Photochemical smog is due to the presence of : oxides of sulphur, oxides of nitrogen, lead, chlorofluorocarbons

RCH = CH_(2) adds on water in the presence of dilute sulphuric acid or phosphoric acid to form

Action of water in the presence of sulphuric acid with the following alkenes (i) (ii) CH_(3)-CH=H_(2) gives

Chlorine dioxide reacts with ozone to yield

The presence of ozone in troposphere