Coal burns with

  • flame

  • only glow

  • both flame and glow

  • none of the above


B.

only glow

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Burning of fossil fuels causes pollution. Comment.


The burning of fossil fuels like coal and petroleum products causes a lot of air pollution.

(i) The burning of coal produces air pollution like carbon dioxide, carbon monoxide sulphur dioxide and smoke. Though carbon dioxide is not a poisonous gas but excess of carbon dioxide in the atmosphere can lead to undesirable changes in climate due to increased green house effect. Carbon monoxide and sulphur dioxide are poisonous gases which affect the health of human beings. Sulphur dioxide also leads to acid rain.

(ii) The major air pollutants produced by burning of petrol in automobiles are carbon dioxide, sulphur dioxide, nitrogen oxides and some load compounds. All these pollutants released from the exhausts of the engine into the air are harmful.

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Which of the following has the lowest ignition temperature ?

  • petrol

  • kerosene

  • coal

  • LPG


D.

LPG

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At airports and petrol pumps hydrocarbon fire extinguishers are used, not the soda-acid fire extinguisher. Why ?


At airports or petrol pumps the probability of breaking fire from oils are more. In case of fires due to oils, soda-acid fire extinguisher is not successful, because it uses water to cool the combustible substance. But water is lighter than oil and settles down the oil particles and fire cannot be controlled. In such case Hydrocarbon fire extinguisher is used which has turkey red oil, which causes the foaming of carbon dioxide under pressure. The foam covers the surface of burning substance and cuts off the supply of air to control fire.


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The substances which have very low ignition temperature will

  • catch fire easily

  • will not catch fire

  • catch fire after some time

  • none of the above


A.

catch fire easily

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