List the products of combustion of fossil fuels. What are their adverse effects on the environment ?

Carbon and its Compounds

Combustion of Carbon Compounds

Official Answer

Fossil fuels like coal and petroleum contain carbon, hydrogen, nitrogen, and sulphur.

1. Products of Combustion of Fossil Fuels:

Carbon dioxide ( $CO_2$ ) and Water vapour ( $H_2O$ ) (during complete combustion).
Carbon monoxide ( $CO$ ) (during incomplete combustion in limited oxygen).
Oxides of sulphur ( $SO_2$ , $SO_3$ ) and Oxides of nitrogen ( $NO$ , $NO_2$ ) due to the combustion of sulphur and nitrogen impurities present in the fuels.
Soot/Unburnt carbon particles.

2. Adverse Effects on the Environment:

Global Warming: Excess release of carbon dioxide ( $CO_2$ ), a greenhouse gas, traps solar radiation in the atmosphere, leading to global warming and climate change.
Acid Rain: Oxides of nitrogen and sulphur react with rainwater to form nitric acid and sulphuric acid, resulting in acid rain. This damages soil fertility, aquatic ecosystems, forests, and historical monuments (like the Taj Mahal).
Air Pollution and Respiratory Issues: Carbon monoxide ( $CO$ ) is highly toxic as it binds with hemoglobin, reducing the oxygen-carrying capacity of blood. Fine particulate matter (soot) causes severe respiratory disorders like asthma, bronchitis, and lung congestion.

Carbon dioxideOxides of nitrogenOxides of sulphurCarbon monoxideAcid rainGlobal warmingGreenhouse effectAir pollution

Marking Scheme

1Listing the products of combustion (carbon dioxide, water, oxides of nitrogen, oxides of sulphur, carbon monoxide) (1 mark)
2Explaining at least two adverse environmental effects (global warming, acid rain, air pollution/health hazards) (1 mark)

Hint

Think about the gases released when coal or petrol burns, and how they contribute to global warming, acid rain, and breathing difficulties.

Quick Oral Answer

Q: Why is carbon monoxide considered a highly toxic pollutant? A: Carbon monoxide binds with hemoglobin in our blood to form carboxyhemoglobin, which is much more stable than oxyhemoglobin. This prevents oxygen transport to vital organs, leading to suffocation and even death.

Analysis & Explanation

Fossil fuels are formed from biomass buried deep under the earth over millions of years. Because they originate from organic matter, they contain carbon and hydrogen as primary constituents, along with small amounts of nitrogen and sulphur. When burnt, these elements oxidize to form gaseous pollutants that severely degrade air quality and disrupt ecological balances.

Common Mistakes

1Only mentioning carbon dioxide and water, while omitting the highly polluting oxides of nitrogen and sulphur.
2Confusing carbon monoxide ( $CO$ ) with carbon dioxide ( $CO_2$ ) as the primary cause of global warming.

Interesting Facts

Acid rain can dissolve essential nutrients like magnesium and calcium from the soil, making it difficult for trees and plants to survive.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2012?

This question carries 2 marks in the CBSE Class 10 Science 2012 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Combustion of Carbon Compounds" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2012 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2012 paper.