Tag: combustion

Questions Related to combustion

The colour of the flame in luminous zone is:

chemistry combustion structure of flame flame combustion, fuels and flame

  1. blue

  2. red

  3. yellow

  4. black

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Correct Option: C

The blue zone in a LPG flame indicates _________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. unburnt vapours

  2. partial decomposition

  3. moderately hot

  4. hottest and complete combustion

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Correct Option: D
Explanation:

Flame color determines the rate of combustion and thus the temperature difference producing a different color flame. In LPG the blue zone is the zone of complete combustion of fuel. So, the amount of soot decreases and the temperature is highest as high heat is released.

Match the column I with Column II and select the correct option from the codes given below.

column I Column II
(a) Hottest zone of candle flame (i) Zone of unburunt wax vapours.
(b) Yellow zone of candle flame (ii) Non-luminous zone
(c) Black innermost zone of the candle flame (iii) Incomplete combustion zone/
chemistry combustion structure of flame flame combustion, fuels and flame

  1. (a) - (i), (b) - (ii), (c) - (iii)

  2. (a) - (ii), (b) - (i), (c) - (iii)

  3. (a) - (i), (b) - (iii), (c) - (ii)

  4. (a) - (ii), (b) - (iii), (c) - (i)

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Correct Option: D
Explanation:

The correct match is:- (a) - (ii), (b) - (iii), (c) - (i)
Hottest zone of candle flame $ \rightarrow $ Non-luminous zone.
Yellow zone of candle flame $ \rightarrow $ Incomplete combustion zone.
Black innermost zone of the candle flame $ \rightarrow $ Zone of unburunt wax vapours.

Which is the hottest part of Bunsen flame?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. In the blue zone

  2. Just above the tip of the primary flame

  3. At the top of the outer core

  4. Just above the inner core

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Correct Option: B

Which of the following flames is produced by a candle?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Blue flame

  2. Non-luminous flame

  3. Light giving flame

  4. Yellow luminous flame

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Correct Option: D

Which of the following do not produce flame on burning?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Petrol

  2. Coal

  3. L.P.G

  4. Kerosene

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Correct Option: B
Explanation:

Coal burns directly without getting vaporised. So it does not produce flame. It burns with a glow.

The hottest part of a candle flame is the __________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. luminous zone

  2. dark zone

  3. hot zone

  4. non-luminous zone

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Correct Option: D
Explanation:
The Non-Luminous zone is the region of the complete combustion. If you look at a candle flame closely. You will see an "aura" formed around the candle. Since this zone is complete combustion and it is the hottest part of the flame.

Which is the hottest part in the flame of the candle?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Blue

  2. Yellow

  3. Black

  4. Wax part

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Correct Option: A
Explanation:

The hottest part of a candle flame are actually the blue, almost invisible area near the base. Where oxygen is drawn in and blue or white part around the edge. In this area flame meets the oxygen-rich air all around it. The flame get progressively cooler as you move in from the outside edge toward the wick.

Colour of the flame is dependent on the ______________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. supply of oxygen

  2. nature of fuel

  3. ignition temperature of the fuel

  4. All of the above

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Correct Option: B
Explanation:

The colour and temperature of a flame are dependent on the nature of the fuel involved in the combustion.

When excited, every element can emit light; the wavelength, and hence the colour, of the emitted light, is characteristic of each element. An example of this is the blue flame from gas ovens, which is due to the combustion of methane or liquified petroleum gas.

During burning of candle, different zones of combustion in the flame are listed below:-


a) Outermost zone
b) Innermost zone
c) Middle zone

The correct order of temperature of zones is :

chemistry combustion structure of flame flame combustion, fuels and flame

  1. $A>B>C$

  2. $C>B>A$

  3. $B>C>A$

  4. $A>C>B$

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Correct Option: D
Explanation:

The flame consist of three zones: 

  1. The outermost zone is the hottest among the 3 and is blue in colour.
  2. The middle zone is moderately hot and is yellow in colour.
  3. The innermost zone is the least hot and black in colour.