Question

(a) What do you mean by Greenhouse effect? What is the role of CO₂ in greenhouse effect?

(b) A factory was started near a village. Suddenly villagers started feeling the presence of irritating vapours in the village and cases of headache, chest pain, cough, dryness of throat and breathing problems increased. Villagers blamed the emissions from the chimney of the factory for such problems. Explain what could have happened. Give chemical reactions for the support of your explanation.

Answer 1

(a) Greenhouse effect: It is the phenomenon in which earth's atmosphere traps the heat from the sun and prevents it from escaping into the outer space. Greenhouse gases such as CO₂, methane, ozone, chlorofluorocarbon (CFC) compounds and water vapour in the atmosphere result in climatic changes. Heat from sun is absorbed by the earth and this heat is reemitted by the earth which is absorbed by CO₂ and then radiated back to earth which results in global warming.

(b) The symptoms observed in the villagers show that oxides of nitrogen and sulphur must be coming out of the chimney. This is due to combustion of fossil fuels like coal, oil, natural gas, gasoline, etc. to produce high temperatures at which oxidation of atmospheric nitrogen takes place forming NO and NO₂.

N₂ + 2NO + O₂ \(\overset{1200-1750^oC}\rightleftharpoons\) 2NO ;

O₂ \(\overset{1100^oC}\rightleftharpoons\) 2NO₂

SO₂ is produced due to combustion of sulphur containing coal and fuel oil or roasting of sulphide ores like iron pyrites (FeS), copper pyrites (CuFeS₂), etc.

Cu₂S + O₂ → 2Cu + SO₂.