NCERT Solutions for Class 11 Chemistry Chapter 14 Environmental chemistry

Ans : Environmental chemistry is the study of chemical and biochemical processes occurring in nature. It deals with the study of origin, transport, reaction, effects, and fates of various chemical species in the environment. 

Ans : Tropospheric pollution arises due to the presence of undesirable substances in the lowest layer of the atmosphere. 
Oxides of sulphur, nitrogen, carbon, and hydrocarbons are the major gaseous pollutants. Oxides of sulphur (\( \mathrm{SO}_{2}\)md SO,) and nitrogen (\( \mathrm{NO}_{2}\), NO) are produced as a result of burning of fossil fuels (coal, automobile fuel). These oxides react with water in the presence of atmospheric oxygen to form nitric acid (HN03) and sulphuric acid \( \mathrm{H}_{2} \mathrm{SO}_{4}\), which leads to the formation of 'Acid rain'. 
\( 2 \mathrm{SO}_{2(g)}+\mathrm{O}_{2(\mathrm{g})}+2 \mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow 2 \mathrm{H}_{2} \mathrm{SO}_{4(\mathrm{aq})}\)
\(4 \mathrm{NO}_{2(\mathrm{g})}+\mathrm{O}_{2(\mathrm{g})}+2 \mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow 4 \mathrm{HNO}_{\mathrm{y}(\mathrm{aq})}\)


Acid rain causes harm to agriculture, plants, and trees, It also leads respiratory ailments. Hydrocarbons are carbon and hydrogen containing compounds that burn oxides of carbon. Hydrocarbons are carcinogenic md their products are to various to produce also major pollutants. Carbon monoxide \( \mathrm{NO}\) is poisonous in nature as it reacts with the haemoglobin of blood, which can even result in death. Though carbon dioxide \( \mathrm{CO}_{2}\) is not toxic in nature, yet it contributes towards global warming by trapping the reflected IR rays. This results in the heating up of the Earth's atmosphere, thereby leading to the melting of icebergs and glaciers. 
Particulates of smoke, dust, mist, and fume are harmful for human health as they are likely to block the nasal passage of a person, causing respiratory ailments. Smoke and fog combine to produce smog during a cool, humid day, thereby reducing visibility to a large extent. Photochemical smog is formed due to the presence of PAN, ozone, formaldehyde, and acrolein. It causes eye irritation, headaches, and chest pain, It also leads to the cracking of rubber and does damage to plants. 

Ans : Carbon dioxide \( \mathrm{CO}_{2}\) and carbon monoxide  \( \mathrm{CO}\)
gases are emitted during the combustion Of various fuels. Carbon monoxide is poisonous, whereas carbon-dioxide is non-toxic in nature. Carbon monoxide is poisonous because it is capable of forming a complex with haemoglobin (carboxyhemoglobin), which is more stable than the oxygen-haemoglobin complex. The concentration range of 3—4% of carboxyhemoglobin decreases the oxygen-carrying capacity of blood. This results in headaches, weak eyesight, nervousness, and cardiovascular disorders. A more increased concentration may even lead to death. Carbon dioxide is not poisonous. It proves harmful only at very high concentrations. 

Ans : The major greenhouse gases are: 
1) Carbon dioxide \( \mathrm{CO}_{2}\)
2) Methane \( \mathrm{CH}_{4}\)
3) Water \( \mathrm{H}_{2} \mathrm{O}\) 
4) Nitrous oxide  \( \mathrm{NO}\)
5) Ozone \( \mathrm{O}_{3}\)
6) Chlorofluorocarbons (CFCs) 

Ans : Acid rain is a byproduct of various human activities that leads to the emission of oxides of sulphur and nitrogen in the atmosphere. These oxides undergo oxidation and then react with water vapour to form acids. 
\( 2 \mathrm{SO}_{2(g)}+\mathrm{O}_{2(g)}+2 \mathrm{H}_{2} \mathrm{O}_{(l)}\) -> \( 2 \mathrm{H}_{2} \mathrm{SO}_{4(\mathrm{aq})}\)
\( 4 \mathrm{NO}_{2(g)}+\mathrm{O}_{2(g)}+2 \mathrm{H}_{2} \mathrm{O}_{(l)}\) -> \( 4 \mathrm{HNO}_{3(\mathrm{aq})}\)
Acid rain causes damage to buildings and structures made of stone md metal. In India, limestone is a major stone used in the construction of various monuments and statues, including the Taj Mahal. 
Acid rain reacts with limestone as: 
\( \mathrm{CaCO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{CaSO}_{4}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}\)
This results in the loss of lustre and colour of monuments, leading to their disfiguration.