Question

Read the following statements regarding the PAN (peroxyacyl nitrates) and select the correct ones.
(i) It is a secondary pollutant present in photochemical smog.
(ii) It is produced by photochemical reactions between hydrocarbons and nitrogen oxides in the presence of sunlight of UV radiations.
(iii) It is thermally unstable and decomposes into peroxy ethanoyl radicals and nitrogen dioxide gas.
(iv) It is a lachrymatory substance, causing irritation of eyes.
A. (i) and (ii)
B. (iii) and (iv)
C. (i), (ii) and (iii)
D. (i), (ii), (iii) and (iv)

Answer 1

Hint:- Pollutants are defined as the substances or materials that are introduced into any environment brings about undesirable effects and adversely changes or affects the normal atmosphere. They harm the usefulness and degrade the nature of any resources to a harmful limit. It can cause several changes which can be short term or long term and have a negative effect on the different living organisms.

Complete step-by-step solution:-
A pollutant is an extrinsic element that is added to the normal environment and causes various types of ill effects and changes. The pollutants are either natural or are man-made. Natural pollutants are also known as primary pollutants and they arise from natural phenomena such as volcanic eruption, forest fires etc. Man-made or anthropogenic pollutants are more serious in nature as they are produced due to several malpractices by humans. They are also known as secondary pollutants. It is not produced directly but is caused due to the combined effects of several different types of pollutants. Some of the major secondary pollutants are carbon dioxide, sulfur oxides, nitrogen oxides, volatile organic compounds, chlorofluorocarbons and peroxyacyl nitrates.
PAN or peroxyacyl nitrates is a potent secondary pollutant as they are not released into the atmosphere directly. They are formed as a result of chemical reactions of other pollutants. It is present in the photochemical smog which is formed due the reaction of sunlight, nitrogen oxides and volatile compounds present in the atmosphere. It is mostly formed during the summer months with high influx of sunlight and nitrogen oxides emission. PAN or peroxyacyl nitrates are produced when photochemical reactions take place in presence of ultraviolet rays and sunlight and oxidize the unburned hydrocarbons and nitrous oxides.
THe most common radical of peroxyacetyl is peroxyacyl, it disassociates easily and is highly thermally unstable and releases free radicals in form of peroxy ethanoyl radicals and nitrogen dioxide gas.
PAN is both a toxic and irritant pollutant and more easily dissolves in water. They cause eye irritations at concentrations as low as only a few parts per billion. They are thus known as lachrymators. At higher concentrations, they cause skin cancer and are mutagenic.

Therefore, the correct option is option D.

Note:- PAN or peroxyacyl nitrates is a secondary pollutant caused by the effects and reactions of several other pollutants such as volatile compounds and nitrous oxide. When volatile compounds and nitrous oxide react in the presence of sunlight and UV radiation, peroxyacyl nitrates is formed. It is thermally very unstable and releases free radicals of peroxyacetyl nitrates. It is a highly irritant chemical and causes irritation of the eye and is known as lachrymators.