Combustion And Flame Test

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Combustion And Flame Test - 1

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Question 1
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Directions For Questions

Read the statements given below and select the correct option.

...view full instructions

Statement 1: Combustion is a chemical process in which a substance reacts with oxygen to give out heat and light.
Statement 2: Heat and light are produced in the sun due to combustion.

A
Both statements are true and statement 2 is the correct explanation of statement 1.

B
Both statements are true, but statement 2 is not the correct explanation of statement 1.

C
Statement 1 is true and statement 2 is false.

D
Both statements are false.

Solution

Statement 2 is false because nuclear reactions are responsible for the heat and light produced in the sun.
Question 2
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Which of the following options correctly defines calorific value of a fuel?

A
Heat energy liberated by complete combustion of 1 g of fuel

B
Heat energy liberated by complete combustion of 1 kg of fuel

C
1 kJ of energy liberated by complete combustion of any amount of fuel

D
None of these

Solution

The amount of heat produced by the complete combustion of a material or a fuel is called its calorific value.
It is measured in units of energy per amount of material, e.g. kJ/kg.
Question 3
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Analyse the two statements given below and select the correct option.

Statement I: Fuel are energy reserves and this energy is released by the process of combustion.
Statement II: Combustion is the process of burning the substance in the presence of a sufficient quantity of oxygen.

A
Both statements I and II are correct and statement II is the correct reason for I.

B
Both statements I and II are correct, but statement II is not the correct reason for I.

C
Statement I is correct, but statement II is incorrect.

D
Both statements I and II are incorrect.

Solution

Both statements I and II are correct, but statement II is not the correct reason for I.
The correct reason for statement I is that combustion is an exothermic process.
Question 4
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Which of the following options regarding burning of coal is correct?

A
It burns with a flame.

B
It vaporises on heating.

C
It smoulders when hot.

D
It leaves no residue on burning.

Solution

Coal is a solid fuel and it does not vaporise on heating. Hence, it does not burn with a flame, but smoulders on heating.

The initial flame formed is due to the trapped impurities.

Moreover, coal on burning produces solid ash.
Question 5
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Combustion of fuels is

A
an oxidation reaction in the absence of nitrogen

B
an endothermic process

C
a process of chemical combination with atmospheric oxygen

D
an oxidation process in the absence of air

Solution

Combustion of fuel is the reaction of fuel with excess of oxygen to release energy.
Hence, the process is highly exothermic.
Question 6
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In which of the following cases is the use of water as a fire extinguisher inappropriate?

I. In an electrical appliance shop
II. In a newspaper factory
III. In a furniture house

A
Only II and III

B
Only I and II

C
Only I and III

D
Only I

Solution

Water works as a fire extinguisher by lowering the temperature of the fuel below its ignition temperature.

However, it should not be used to put off a fire caused by electric current, as water being a good conductor of electricity could cause an electric shock.

Hence, its use to put off a fire in an electrical appliance shop is inappropriate.
Question 7
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What happens when water is heated in a paper cup?

A
Paper cup burns up without any change in the temperature of water.

B
Paper cup burns up with water undergoing the boiling process.

C
There is no effect on the paper cup or water.

D
Water continues to boil without the paper cup getting burnt up.

Solution

On heating a paper cup containing water, the heat is transferred to the water which begins to boil.

Since all the heat supplied is used up to vaporise water, the paper does not acquire its ignition temperature and hence the cup does not burn up, while the water continues to boil.
Question 8
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Water is used to extinguish fire because it

A
raises the ignition temperature of the burning substance

B
cools the burning substance down to a temperature below its ignition temperature

C
lowers the ignition temperature of the burning substance

D
conducts heat

Solution

Water cools the burning substance down to a temperature below its ignition temperature and as a result, the burning process stops.

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Re-Attempt Weekly Quiz Competition

Combustion And Flame Test - 1

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Combustion And Flame Test - 1

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Question 1

Both statements are true and statement 2 is the correct explanation of statement 1.

Both statements are true, but statement 2 is not the correct explanation of statement 1.

Statement 1 is true and statement 2 is false.

Both statements are false.

Solution

Question 2

Heat energy liberated by complete combustion of 1 g of fuel

Heat energy liberated by complete combustion of 1 kg of fuel

1 kJ of energy liberated by complete combustion of any amount of fuel

None of these

Solution

Question 3

Both statements I and II are correct and statement II is the correct reason for I.

Both statements I and II are correct, but statement II is not the correct reason for I.

Statement I is correct, but statement II is incorrect.

Both statements I and II are incorrect.

Solution

Question 4

It burns with a flame.

It vaporises on heating.

It smoulders when hot.

It leaves no residue on burning.

Solution

Question 5

an oxidation reaction in the absence of nitrogen

an endothermic process

a process of chemical combination with atmospheric oxygen

an oxidation process in the absence of air

Solution

Question 6

Only II and III

Only I and II

Only I and III

Only I

Solution

Question 7

Paper cup burns up without any change in the temperature of water.

Paper cup burns up with water undergoing the boiling process.

There is no effect on the paper cup or water.

Water continues to boil without the paper cup getting burnt up.

Solution

Question 8

raises the ignition temperature of the burning substance

cools the burning substance down to a temperature below its ignition temperature

lowers the ignition temperature of the burning substance

conducts heat

Solution

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