Tag: combustion and flame

Questions Related to combustion and flame

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that __________.

chemistry combustion and flame fuels fuel and effects of burning fuel study of combustion

  1. the food is not cooked completely

  2. the fuel is not burning completely

  3. the fuel is wet

  4. all of the above

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Correct Option: B
Explanation:

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that the fuel is not burning completely. When the fuel burns completely giving a blue flame, the bottom of the vessel remains clean. 


When the fuel does not burn completely then a sooty flame appears which makes the bottom of the utensil black. It is due to the air holes, which are getting blocked and the fuel does not burn completely.

Which of the following is most harmful for human body?

chemistry combustion and flame fuels fuel and effects of burning fuel study of combustion

  1. CO

  2. $CO _2$

  3. Oxides of nitrogen

  4. Lead compounds

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Correct Option: D

Why is CNG a cleaner fuel?

chemistry combustion and flame fuels fuel and effects of burning fuel study of combustion

  1. No particulate emission

  2. Releases very less amounts of sulphur and nitrogen oxides

  3. No emission of ash

  4. All of the above

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Correct Option: D
Explanation:

C.N.G (compressed natural gas) is a cleaner fuel because it causes less pollution by emitting fewer pollutants like carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, particulate matter, unburned hydrocarbons etc.

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.

Innermost zone is the _______.

chemistry combustion and flame structure of flame flame combustion

  1. hottest part

  2. moderately hot part

  3. least hot part

  4. cold part

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Correct Option: C
Explanation:

The innermost zone is the least hot part black in colour. This is due to the unburned wax vapor.

Yellow colour in the flame denotes __________.

chemistry combustion and flame structure of flame flame combustion

  1. outermost part

  2. middle zone

  3. innermost zone

  4. none of these

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Correct Option: B
Explanation:

The middle zone is moderately hot and is yellow in color. This is because of partial combustion.