Question

The pollutants which come directly in the air from sources are called primary pollutants. Primary pollutants are sometimes converted into secondary pollutants. Which of the following belongs to secondary air pollutants?

Options

• CO

• Hydrocarbon

• Peroxyacetyl nitrate

• NO

Answer 1

Peroxyacetyl nitrate

Explanation:

Since \[\ce{NO2 (g) ->[hv] NO (g) + [O]}\]  .......(i)

Oxygen atoms are very reactive and combine with the O₂ in air to produce ozone.

\[\ce{[O] + O2 (g) -> O3 (g)}\]  .......(ii)

The ozone formed in the above reaction (ii) reacts rapidly with the NO(g) formed in the reaction (i) to regenerate NO₂. NO₂ is a brown gas and at sufficiently high levels can contribute to haze.

\[\ce{NO (g) + O3 (g) -> NO2 (g) + O2 (g)}\]

Ozone is a toxic gas and both NO₂ and O₃ are strong oxidizing agents and can react with the unburnt hydrocarbons in the polluted air to produce chemicals such as formaldehyde, Acrolein and peroxyacetyl nitrate (PAN) etc.