Tag: combustion

Questions Related to combustion

Middle zone is the hottest zone of a flame.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. True

  2. False

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Correct Option: B
Explanation:

The outermost zone in the candle flame is the hottest zone owing to the fact that complete combustion has taken place in this region.

The substances which vapourise during burning, give flame.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. True

  2. False

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Correct Option: A
Explanation:

True.
Combustible substances that vaporize during combustion give flames. So flame is nothing but the hot ignited glowing gas formed during combustion.

Artificial rubies and sapphires can be made by heating alumina in ?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. An oxy-hydrogen flame

  2. An oxy-acetylene flame

  3. Burning methane

  4. An electric furnace

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Correct Option: A
Explanation:

Artificial ruby and sapphires are manufactured from alumina to which 1.5% of magnetic iron oxide and 0.5% of titanium oxide has been added, the mixture is fused and crystallised in an oxy-hydrogen flame. It is a reducing flame.

A lilac-coloured flame is produced on heating.

chemistry combustion structure of flame flame combustion, fuels and flame

  1. Potassium in a flame

  2. Cobalt in a flame

  3. Sodium in a flame

  4. Methane in oxygen

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Correct Option: A
Explanation:
Potassium on heating produced lilac-colured flame because on heating, an atom entities its electrons and they jump to higher energy levels. When the electron return to lower energy levels, they emit energy in the form of light. The colour produced on heating depends upon wavelength of emitted light.

If you watch a burning candle carefully, you will find different colurs in the flame. Which is the hottest part of the candle flame?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. The middle orange part

  2. The middle, yellow part

  3. The outermost portion that is blue

  4. The innermost black zone

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Correct Option: C
Explanation:

The outermost portion that is blue.

The hottest part of the candle flame is the blue part, at $1670^oF$ ($1400^oC$) i.e., the outermost portion, where the flame has the most oxygen and you are getting complete combustion.

The flame of the candle has three zones. The outer zone is blue, the middle zone is yellow and the inner zone is black. Which is correct regarding this?

chemistry combustion structure of flame flame combustion, fuels and flame

  1. The outer zone is hottest hot.

  2. The middle zone is hottest

  3. The inner zone is least hot

  4. All the zones have same temperature

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Correct Option: A,C
Explanation:

Candles produce light by releasing heat. A candle flame consists of three zones. Each zone has different temperatures and colors.

  • The first zone is called the Outer zone
  • The second zone is called the Middle zone
  • The third zone is called the Inner zone

The outer zone is blue in color, due to complete combustion,. This zone is the hottest zone.

The middle one is in yellow color, which is the bright part of the flame. It is moderately hot and partial combustion of fuel takes place.

The least hot region of the flame is innermost zone. This inner zone is black in color due to the presence of unburnt wax vapors.

What is the maximum possible temperature( in $^0 C$) of a Bunsen burner flame? Assume that the gas is pure methane and that it is pre-mixed with sufficient air to permit complete combustion.

chemistry combustion and flame structure of flame flame combustion

  1. 1500

  2. 4000

  3. 5000

  4. 1100

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Correct Option: A

Burning of coal and wood causes  _____________.

chemistry combustion and flame structure of flame flame combustion

  1. pollution of air

  2. decrease of non-renewable source of energy 

  3. both (a) and (b)

  4. neither (a) or (b).

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Correct Option: C
Explanation:

Burning of coal and wood causes air pollution and because of burning of coal and wood there is decrease in amount of non-renewable sources. 

The zone of no combustion is _______.

chemistry combustion and flame structure of flame flame combustion

  1. The middle zone

  2. Outermost zone

  3. The base of the flame

  4. Innermost zone

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Correct Option: D
Explanation:

Innermost zone is the zone of no combustion. It is also called as dark zone which is formed around the wick of the candle flame.

Substance which vaporize during burning gives ____________.

chemistry combustion and flame structure of flame flame combustion

  1. sound

  2. flame

  3. combustion

  4. none of these

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Correct Option: B
Explanation:

Substances which vaporize during burning gives flame. For example, combustion of kerosene oil produces a flame. On the other hand, certain substances like coal do not vaporize and hence does not produce a flame.