Tag: combustion

Questions Related to combustion

How many zones are present in candle flame? 

chemistry combustion structure of flame flame combustion, fuels and flame

  1. 2

  2. 3

  3. 4

  4. 5

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Correct Option: B
Explanation:

A flame consist of three zones. These are the Innermost zone, middle zone, outer zone. The three zones of a flame have different colours and different temperature.


Hence, option B is correct.

Why the innermost zone of candle flame is the least hot?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Unburnt wax vapour

  2. No supply of oxygen

  3. Presence of wick

  4. All the above

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Correct Option: A
Explanation:

Dark zone is directly above the wick and wax gets vaporized at this region but does not undergo burning.


Hence the option A is correct.

What type of materials gives flame?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. All materials 

  2. Materials which vaporise on heating

  3. Materials which melt on heating

  4. None of the above

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Correct Option: B
Explanation:

The material which vaporizes on burning is capable of producing flame.


Hence the option B is correct.

Unburnt carbon particles are present in the:

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Blue zone

  2. Dark inner zone

  3. Luminous zone

  4. Non-luminous zone

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Correct Option: C
Explanation:
The circular dark ring is formed on the slide is due to the deposition of unburnt carbon particles present (middle) in the luminous zone of the candle.

Which of the following elements give light green colour in flame test ?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. $ K $

  2. $ Rb $

  3. $Ca $

  4. $ Ba $

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Correct Option: D
Explanation:

Barium gives light green or apple green colour in flame test. This is the preliminary test for detecting Barium in any salt mixture.

In LPG cylinder, the gas is liquefied by ___________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. increasing volume

  2. applying pressure

  3. increasing temperature

  4. none of the above

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Correct Option: B

Which of the following statement is NOT true?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Flame can be seen over burning solids and liquids

  2. Type of flame depends upon the amount of oxygen available

  3. Invisible zone of a flame is the least hot zone

  4. Blue-zone indicates complete combustion of fuel

Show answer
Correct Option: C
Explanation:

The Invisible-zone of the flame is also called as non-luminous zone which is the zone of complete combustion. Due to complete combustion the zone become hottest zone of the flame.

Type of flame produced by a fuel depends upon _________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. calorific value

  2. amount of oxygen

  3. type of fuel and its chemical composition

  4. all of the above

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Correct Option: B
Explanation:

Type of flame depends upon the amount of oxygen available for burning of the fuel. If oxygen is present in sufficient amount it is called as oxidizing flame but oxygen is not available in sufficient amount it is called as reducing flame.

A material when burnt gives out flame because of _________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. vapourisation

  2. melting

  3. combustibility

  4. conductivity

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Correct Option: C

A circular blackish ring on the glass plate kept over the candle flame indicates ___________.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Complete combustion

  2. Dark zone of the flame

  3. Non-luminous zone

  4. Luminous zone

Show answer
Correct Option: D
Explanation:

A circular blackish ring on the glass plate kept over the candle flame indicates the luminous zone. The candle flame consists of mainly 3 zones depending on the temperature i.e the outer zone ( hottest among all, blue in colour, complete combustion occurs here and is the non-luminous part of the flame), middle zone ( moderately hot, yellow in colour, partial combution), inner zone (least hot and black in colour, and is the luminous part).