Photochemical smog formed in congested metropolitan cities mainly consists of :

Options

A. Ozone, peroxyacetyl nitrate and `NO_3`
B. Smoke , peroxyacetyl nitrate and `SO_2`
C. Hydrocarbons, `SO_4` and `CO_3`
D. Hydrocarbons , ozone and `SO_2`

Answer

A

Explanation

Photochemical smog mainly consists of ozone, peroxyacetyl nitrate and different oxide of nitrogen and hydrocarbons released from different engines. Nitric oxide (NO) is formed by reaction between oxygen and nitrogen. This reacts with air forming nitrogen dioxide `(NO_2)`. This gas absorbs light due to which nitric oxide (NO) and a molecule of nascent oxygen [O] are formed.
`NO_2 to NO+[O]`
This atomic oxygen reacts with unburnt hydrocarbons to give rise to peroxy radicals which after reaction with oxygen from ozone or reacting with `NO_2` give rise to peroxyacetyl nitrate (PAN).