Combustion and Flame - Chapter Wise CBSE Solved Question and Answer Based On NCERT
Long Q&A:
Q1: Explain the advantages of CNG as fuel.
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Ans:
The use of diesel and petrol as fuels in automobiles is a major cause of air pollution to day. During combustion, these fuel release unburnt carbon particles which are highly poisonous and harmful for living beings and environment. These fine particles are dangerous pollutants causing respiratory diseases, such as asthma. Incomplete combustion of these fuels gives carbon monoxide gas. It is a very poisonous gas. Combustion of most fuels releases carbon dioxide in the environment. Increased emission of carbon dioxide in the air is one of the major causes for global warming.The use of diesel and petrol as fuels in automobiles is being replaced by CNG (Compressed Natural Gas), because CNG produces the harmful products in very small amounts. CNG is a cleaner fuel. It has high fuel efficiency. Hence use of CNG in automobiles has reduced pollution in our cities to a noticeable extent.
Q2: Differentiate between LPG and wood as fuel.
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Ans:
LPG
WOOD
It is costly fuel, but readily available and easy to transport in cylinders and tankers
It is more energy efficient
Its calorific value is 55000 kJ/kg
It causes less air pollution and prevent deforestation by supplementing the fuel need in place of wood as fuel.
It is an exhaustible natural resource.
It is cheap fuel but not readily available in cities and not readily combustible
It is less energy efficient
Its calorific value is 17000- 25000Kj/kg
It causes air pollution and deforestation
It is not an exhaustible natural resource as trees can be grown in 5-10 years
Q3: Explain working and principles of a fire extinguisher.
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Ans:
The most commonly used fire extinguisher is water, it works when wood and paper are on fire, but if electrical equipment is on fire water may conduct electricity and may harm those trying to douse the fire, also water is not suitable for fires involving oil and petrol, since water is heavier than oil it sinks below the oil and oil keeps burning on the top. So if electrical equipment and inflammable materials are on fire Carbon dioxide is the best extinguisher. Since it is heavier than oxygen it covers the fire so that the contact between fuel and oxygen is cut off and the fire is controlled, it also bring s down the temperature of the fuel. For this purpose carbon dioxide is stored at high pressure as a liquid in cylinders.
Q4: Explain why the process of rusting can be called as slow combustion
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Ans:
Rusting of iron is a slow oxidation process in which iron using oxygen and water is oxidised and is rusted out, it produces heat at very slow rate. The combustion process is also an oxidation process and is a chemical reaction by which a fuel and an oxidiser react to produce heat and light, thus we can say rusting of iron is a slow combustion process, although combustion is much faster than rusting.
