Tag: chemistry

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Multiple choice chemistry combustion structure of flame flame combustion, fuels and flame

Unburnt carbon particles are present in the:

  1. Blue zone

  2. Dark inner zone

  3. Luminous zone

  4. Non-luminous zone
Reveal answer Fill a bubble to check yourself
C Correct answer
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.
Multiple choice chemistry combustion structure of flame flame combustion, fuels and flame

In LPG cylinder, the gas is liquefied by ___________.

  1. increasing volume

  2. applying pressure

  3. increasing temperature

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

LPG (Liquefied Petroleum Gas) is stored in cylinders under high pressure, which forces the gas molecules together to change their state from gaseous to liquid.

Multiple choice chemistry combustion structure of flame flame combustion, fuels and flame

Which of the following statement is NOT true?

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

Multiple choice chemistry combustion structure of flame flame combustion, fuels and flame

Type of flame produced by a fuel depends upon _________.

  1. calorific value

  2. amount of oxygen

  3. type of fuel and its chemical composition

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

Multiple choice chemistry combustion structure of flame flame combustion, fuels and flame

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

  1. Complete combustion

  2. Dark zone of the flame

  3. Non-luminous zone

  4. Luminous zone
Reveal answer Fill a bubble to check yourself
D Correct answer
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).

Multiple choice chemistry combustion structure of flame flame combustion, fuels and flame

The blue zone in a LPG flame indicates _________.

  1. unburnt vapours

  2. partial decomposition

  3. moderately hot

  4. hottest and complete combustion
Reveal answer Fill a bubble to check yourself
D Correct answer
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.