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Important questions on Combustion

What is meant by rapid combustion ? Give an example.

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Rapid Combustion is a form of combustion , otherwise known as fire, in which large amounts of heat & light energy are released, which often results in a flame.
Example :- Burning of matchstick, Combustion of LPG.

I: When a hydrocarbon is combusted in air, carbon monoxide is the major product
II: A
ir contains much more nitrogen than oxygen.

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When a hydrocarbon is combusted in air, carbon monoxide is the major product.

 Air contains much more nitrogen than oxygen.

Both the statements are correct and the statement II is correct explanation for statement 1
So the answer would be TTCE.

Give reasons
(a) Water is not used to control fires involving electrical equipment.
(b) LPG is a better domestic fuel than wood.
(c) Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.

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(a) Water is a conductor of electricity, so it can easily conduct electric current and cause danger of electric shocks or short-circuits. Therefore, water can not be used to control the fire involving electrical equipment.
(b) LPG is a better domestic fuel as it does not produce smoke and unburnt carbon particles, which cause respiratory problems.
(c) Paper by itself catches fire easily because it has low ignition temperature but when wrapped around an aluminium pipe its temperature is lowered due to aluminium metal absorbing the heat supplied to paper. So it does not catch fire.

The heat evolved in the combustion of glucose, is . The mass of produced, when of heat is evolved in the combustion of glucose is

A

B

C

D

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Why does coal not burn by itself in air, but once initiated by a flame, continues to bum?

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Activation energy for the combustion reaction is very high and is not available at room temperature.

On applying flame, to a part of the coal and air in contact with the flame absorb heat which provides the necessary activation energy and combustion starts. The heat liberated further provide activation energy for the combustion to continue.

What does the above experiment show ?

A

The direction of movement of hot and cold air.

B

Oxygen is present in the air and is necessary for burning.

C

The temperature of air inside the bottle is more than the temperature of open air.

D

The direction in which the maximum smoke is produced & pollutes the environment.

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When you lit the candle the first time you did it in an area where the air pressure was constant, so the smoke flowed straight up. When you set the pans side by side, the ice cooled the air around it, creating a mini high-pressure zone, and the sand warmed the air around it to create a mini low-pressure zone. Air always flows from a high-pressure zone to a low-pressure zone to even up the pressure. You made a tiny breeze between the pan of ice and the pan of sand, and the smoke floated sideways in the breeze. The same thing happens between cold ocean water and hot beach sand.
Air pressure changes cause wind, but they are responsible for other types of weather too. A low-pressure zone usually causes clouds and rain, because as the hot air rises it carries with it evaporated moisture that can condense into clouds. A high-pressure zone usually results in clear skies and sunny days because sinking currents prevent moisture from rising up and forming clouds.

Which type of fire extinguisher is used to extinguish fire caused by burning oil and petrol?

A

foam type

B

water type

C

soda acid type

D

type

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In foam type fire extinguisher _______ is responsible to put off fire.

A

B

C

D

View Answer

The chemical reaction that takes place produces carbon dioxide gas under pressure. The carbon dioxide gas forces itself out through the internal pipe of the nozzle. As the percentage of carbon dioxide in air increases, the air supply is reduced and thus the fire is extinguished.