Tag: chemistry

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Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

Some uses of chlorine and bromine are given.
Which is a use of bromine?

  1. making bleaches for textiles and the the paper industry

  2. making CFC's

  3. making flame retardants and fire extinguishers

  4. making the polymer PVC
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In general, the stability of bromine in a typical flame retardant molecule means that the molecule can offer the highest activity as a flame active retardant, while also being cost effective.  The choice of flame retardant systems for any particular application depends on how the material decomposes in a fire, as well as the materials’ physical property. Brominated flame retardants, because they act in the flame, can be used in just about every application.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

 $CO _2$ is able to control fires by disconnecting the supply of oxygen.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Carbon dioxide is heavier than oxygen. Due to this, carbon dioxide forms a blanket around the burning material and makes a barrier between the burning material and oxygen. As oxygen supply is cutoff, it helps in extinguishing the fire.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

When water is poured over burning wood, the fire goes off. This is because _________.

  1. temperature of wood decreases

  2. temperature of water goes up

  3. molecules of water reacts with oxygen present in the flame

  4. the flame vapourises
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water, when poured over fire absorbs large amount of heat and hence the temperature of wood falls below the ignition temperature. Thus the fire goes off.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

Fire is extinguished by __________.

  1. removing all combustible substance

  2. cutting off a supply of air

  3. cooling the burning substance

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Fire is extinguished by  :
(A) Removing all combustible substance. Fuel is one of the requirements for producing fire. In the absence of fuel, combustion will not occur.
(B) Cutting off a supply of air. Air (oxygen) is essential for combustion. In the absence of air, combustion will not occur.
(C) Cooling the burning substance. This reduces the temperature below its ignition temperature. The fire will not spread.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

Fire can be extinguished by spraying: 

  1. carbon dioxide

  2. carbon tetrachloride

  3. water

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Fire can be extinguished by spraying, carbon dioxide, carbon tetrachloride or water.
Note:
Fire is extinguished by
(A) removing all combustible substance. Fuel is one of the requirements for producing fire. In the absence of fuel, combustion will not occur.
(B) cutting off the supply of air. Air (oxygen) is essential for combustion. In the absence of air, combustion will not occur.
(C) cooling the burning substance. This reduces the temperature below its ignition temperature. The fire will not spread.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

How will you distinguish between fire extinguishing action of water and $CO _2$? 

  1. Water helps to extinguish a fire in two ways: (1) It brings the temperature of the combustible material below its ignition temperature. (2) The water vapour formed due to the heat of fire cuts the supply of oxygen.

  2. Carbon dioxide is highly volatile. So, it immediately vaporises to cut off the supply of air. In the absence of supporter of combustion, fire is extinguished.
  3. Both $A$ and $B$

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both options A and B describe the difference between fire extinguishing action of water and $CO _2$.

  • Water helps to extinguish a fire in two ways: it cools the substance that undergoes combustion and brings the temperature of the combustible material below its ignition temperature. The water vapor formed due to the heat of fire surrounds the substance that undergoes combustion and cuts the supply of oxygen. 
  • Carbon dioxide is highly volatile and it is heavier than oxygen. So, it immediately vaporizes to cut off the supply of air. In the absence of supporter of combustion, fire is extinguished. Also, it does not damage electrical equipment.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

______ is the extinguisher used for inflammable material like petrol.

  1. Water
  2. $CO _2$

  3. Oil

  4. Dry powder
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Some Class-B fires (hydrocarbons, petroleums, and fuels on fire) cannot be efficiently controlled with water. $CO _2$ being heavier than oxygen covers the fire like a blanket. Hence, one of the important factor for fire is cut off and the fire is controlled.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

When paper is wrapped around an aluminium pipe ____________.

  1. ignition temperature reduces

  2. ignition temperature increase

  3. no change in ignition temperature

  4. the paper and aluminium catches fire very easily
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The ignition temperature of paper is lower compared to that of aluminium. When paper is wrapped around an aluminium pipe; the ignition temperature increases. That is why paper itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

Which of the following is a constituent of foam type fire extinguisher?

  1. Dilute sulphuric acid

  2. Sodium carbonate

  3. Dilute hydrochloric acid

  4. All of above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The foam type of fire extinguisher is also called as soda acid fire extinguisher. It consists of dilute sulphuric acid and sodium bicarbonate (soda). When it is released under high pressure in the form of foam, it covers the surface of fire and controls it by cutting off oxygen.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

The lowest temperature at which a substance catches fire?

  1. Flammable temperature

  2. Ignition temperature

  3. inflammable temperature

  4. None of above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ignition temperature is the lowest temperature at which a combustible substance when heated (as in a bath of molten metal) takes fire in air and continues to burn. It is also called also autogenous ignition temperature.