Combustion and Flame Test

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Combustion and Flame Test - 6

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Weekly Quiz Competition

Question 1
1 / -0

Inspite of the danger involved with hydrogen, it is used for some applications. Where is it used?

A
Rocket fuel

B
Oxyhydrogen flame

C
Car fuel

D
All of the above

Solution

Though hydrogen is a highly combustible gas, because of its high calorific value, it is used as rocket fuel, for cutting and welding metals in the form of oxyhydrogen flame and as a car fuel under stringent safety conditions.
Question 2
1 / -0

A family consumes 12 kg of L.P.G. in 30 days. Calculate the average energy consumed per day, if the calorific value of L.P.G. is 50 kJ kg1.

A
10,000 J per day

B
15,000 J per day

C
20,000 J per day

D
25,000 J per day

Solution

Energy released by 12 kg of L.P.G. in 30 days

= No. of kg of gas utilized by a family in 30 days × calorific value of gas.

= 12 / 30 × 50 = 20kJ/day.

Therefore, energy consumed per day:

= 20,000 joules/day.
Question 3
1 / -0

What ignition temperature does an inflammable substance have?

A
More than 100°C

B
Less than 100°C

C
More than 200 °C

D
Between 200 °C to 350 °C

Solution

Inflammable substances have very low ignition temperatures, so they catch fire easily.

e.g., alcohol, ether, carbon disulphide, benzene, synthetic fibres etc.
Question 4
1 / -0

What is the disadvantage of incomplete combustion of a fuel?

A
Unburnt carbon gets released.

B
Air gets polluted.

C
Respiratory problems arise.

D
All of the above

Solution

Incomplete combustion of a fuel results in the formation of unburnt carbon and some poisonous gases like′CO′ and oxides of nitrogen which cause air pollution leading to many respiratory problems.
Question 5
1 / -0

Which of the following is the best extinguisher for inflammable materials?

A
Water

B
Sulphur dioxide

C
Carbon dioxide

D
Carbon monoxide

Solution

Carbon dioxide is the best extinguisher for inflammable materials like petrol, because it is heavier than oxygen, it covers fire like a blanket. Since, the contact between the fuel and oxygen is cut off, the fire is controlled. Secondly, it does not harm the electrical equipment. It can also be used to put out fires involving electrical equipment.
Question 6
1 / -0

On which of these factors does the flame produced by a fuel depend upon?

A
Calorific value

B
Amount of oxygen

C
The chemical composition of a fuel

D
All of the above

Solution

The type of fuel involved in the combustion determines the type of flame (colour and temperature of a flame varies with the chemical composition of the fuel).
Question 7
1 / -0

Which of the following statements is NOT true?

A
CO₂is the best fire extinguisher.

B
Global warming can cause acid rain.

C
Burning of coal and diesel releases sulphur dioxide gas

D
L.P.G. has higher calorific value than biogas.

Solution

Global warming may cause glaciers to melt, which may lead to a rise in the sea level and thus submerge low lying areas.
Question 8
1 / -0

Why is L.P.G, used as domestic fuel, mixed with a strong smelling volatile liquid like mercaptan?

A
For better combustion

B
For good smell/fragrance

C
For detection of gas leakage

D
For higher calorific value

Solution

Butane is an odourless gas, so it is mixed with mercaptan such that if the gas leaks in air, it can be easily detected due to its peculiar choking smell and prevents it from explosion.
Question 9
1 / -0

Hydrogen gas has the highest calorific value i.e., 150kJ kg⁻¹, yet it is not used as a fuel. Why?

A
It is explosive in nature.

B
It causes storage problem.

C
It causes transportation problem.

D
All of the above

Solution

The availability of hydrogen is less and also forms an explosive mixture with air or oxygen and causes explosion if it leaks out. Its storage and transport are difficult.
Question 10
1 / -0

When wood is used as a fuel in chullahs, gaps are left in between logs of wood. Why is it done so?

A
To facilitate movement of air

B
To prevent more consumption of wood

C
To control temperature

D
All of these

Solution

Gaps are left in between logs of wood placed in chullahs to allow free movement of air, which helps in combustion.
Question 11
1 / -0

For a spontaneous combustion to take place, which condition given below is necessary?

A
Flame

B
Low ignition temperature

C
Rise in temperature

D
Temperature below 30°C

Solution

For spontaneous combustion to take place, a substance should have low ignition temperature:

e.g., The ignition temperature of phosphorus is 35° C.
Question 12
1 / -0

An electric spark is struck between two electrodes placed near each other, inside a closed tank full of petrol. What will happen?

A
Spontaneous combustion of petrol

B
Explosion

C
Slow combustion of petrol

D
Nothing will happen

Solution

A tank filled with petrol implies there is no air/oxygen inside the tank. As there is no supporter of combustion, burning of petrol does not takes place though spark is brought nearer to it.
Question 13
1 / -0

One gram of which of these will give out the maximum amount of heat by complete combustion?

A
Wood

B
Coal

C
Diesel

D
Biogas

Solution

Diesel will give out maximum amount of heat by complete combustion when compared with wood, coal and biogas.
Question 14
1 / -0

What are the essential requirements for a fire to start and continue?

(i) Fuel
(ii) Air (oxygen)
(iii) Heat

A
Only (i) and (ii)

B
Only (ii) and (iii)

C
Only (i) and (iii)

D
(i), (ii) and (iii)

Solution

A fire needs fuel, air (oxygen which supports combustion), and heat to raise the temperature of the fuel beyond ignition temperature.
Question 15
1 / -0

Which of the following statements is NOT true?

A
Spontaneous combustion takes place without any apparent cause.

B
The luminous zone of a flame has high temperature.

C
Carbon dioxide gas causes global warming.

D
The calorific value of a fuel is expressed in kJ/kg⁻¹.

Solution

St is not the luminous zone but the non- luminous zone of the flame that has a very high temperature.

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Re-Attempt Weekly Quiz Competition

Combustion and Flame Test - 6

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Combustion and Flame Test - 6

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SHARING IS CARING

Question 1

Rocket fuel

Oxyhydrogen flame

Car fuel

All of the above

Solution

Question 2

10,000 J per day

15,000 J per day

20,000 J per day

25,000 J per day

Solution

Question 3

More than 100°C

Less than 100°C

More than 200 °C

Between 200 °C to 350 °C

Solution

Question 4

Unburnt carbon gets released.

Air gets polluted.

Respiratory problems arise.

All of the above

Solution

Question 5

Water

Sulphur dioxide

Carbon dioxide

Carbon monoxide

Solution

Question 6

Calorific value

Amount of oxygen

The chemical composition of a fuel

All of the above

Solution

Question 7

CO2 is the best fire extinguisher.

Global warming can cause acid rain.

Burning of coal and diesel releases sulphur dioxide gas

L.P.G. has higher calorific value than biogas.

Solution

Question 8

For better combustion

For good smell/fragrance

For detection of gas leakage

For higher calorific value

Solution

Question 9

It is explosive in nature.

It causes storage problem.

It causes transportation problem.

All of the above

Solution

Question 10

To facilitate movement of air

To prevent more consumption of wood

To control temperature

All of these

Solution

Question 11

Flame

Low ignition temperature

Rise in temperature

Temperature below 30°C

Solution

Question 12

Spontaneous combustion of petrol

Explosion

Slow combustion of petrol

Nothing will happen

Solution

CO₂is the best fire extinguisher.

The calorific value of a fuel is expressed in kJ/kg⁻¹.