CBSE Questions for Class 8 Chemistry Combustion And Flame Quiz 8 - MCQExams.com

The hottest region of Bunsen flame shown in the figure below is:

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  • region 2
  • region 3
  • region 4
  • region 1
Which chemical substance is emitted in car exhaust and is a cause of acid rain?
  • Nitrogen oxides
  • Lead
  • Carbon dioxide
  • DDT
  • Nitrates
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Assertion is incorrect but reason is correct
$$I$$. The most significant way in which humans are exposed to mercury is through drinking water.
$$II$$. A great deal of mercury enters the atmosphere because of coal-burning power plants.
  • Statement $$I$$ is true, Statement $$II$$ is true
  • Statement $$I$$ is true, Statement $$II$$ is false
  • Statement $$I$$ is false, Statement $$II$$ is true
  • Statement $$I$$ is false, Statement $$II$$ is false
  • Statement $$I$$ is true, Statement $$II$$ is true and is a correct explanation of the phenomena described in $$I$$
State whether true or false:
We can use water as a fire extinguisher for fires involving petrol.
  • True
  • False
A good fuel has these qualities:
  • should have high calorific value
  • should be costly
  • should cause any pollution
  • should be easy to transport
How water helps in extinguishing fire?
  • Water cools the combustible material so that its temperature is brought below the ignition temperature.
  • Water heats the combustible material so that its temperature is brought below the ignition temperature.
  • Water cools the combustible material so that its temperature is brought above the ignition temperature.
  • None of these
The elements that are combustible in the fuel are:
  • carbon and hydrogen
  • carbon, hydrogen and ash
  • carbon, hydrogen and sulphur
  • carbon, nitrogen and ash
During burning of candle, different zones of combustion in the flame are listed below:-
a) Outermost zone
b) Innermost zone
c) Middle zone

The correct order of temperature of zones is :
  • $$A>B>C$$
  • $$C>B>A$$
  • $$B>C>A$$
  • $$A>C>B$$
What reactant must be present for a reaction to be classified as combustion?
  • $${Cl}_{2}$$
  • $${CH}_{4}$$
  • $${O}_{2}$$
  • $${CO}$$
Which kind of material is extinguished by water on burning?
  • Wood
  • Paper
  • Petrol
  • Both a and b
  1. What is geothermal energy ?
  • Ocean thermal energy
  • Interior heat of the earth.
  • Energy obtained from the heat of hot dry rocks
  • None of these
Fire extinguishers containing $$CO_2$$ are the best extinguishers for fires involving electrical equipment:
  • because $$CO_2$$ being heavier than oxygen covers the fire like a blanket.
  • because $$CO_2$$ being heavier than oxygen increases fire.
  • because $$CO_2$$ being lighter than oxygen covers the fire like a blanket.
  • None of these
How carbon dioxide is stored in the house to extinguish fire?
  • It can store in the bottles
  • It can store in the cylinders under high pressure
  • It can store in canes
  • It can not store in any form
The unit of calorific value is:
  • kJ/kg
  • kg/kJ
  • mg/kJ
  • g/kJ
A thin paper cup filled with water does not catch fire when placed over a flame. This is because:
  • the water cuts off oxygen supply to the paper cup
  • water is an excellent conductor of heat
  • the paper cup does not reach to ignition temperature
  • paper is a poor conductor of heat
The cooking gas burns rapidly and produces heat and light. Such combustion is called _________.
  • rapid combustion
  • incomplete combustion
  • regular combustion
  • none of these
Choose the correct answer from the alternatives given.
In an atomic explosion, enormous energy is released due to _______________.
  • Conversion of light energy into hear energy
  • Conversion of heat energy into light energy
  • Conversion of mechanical energy into nuclear energy
  • Conversion of mass into energy
Which of the following example represents spontaneous combustion?
  • Burning of matchstick.
  • Burning of cooking gas.
  • Ignition of a cracker.
  • Phosphorus burns in air at room temperature
Which of the following example(s) represents rapid combustion?
  • Burning of matchstick.
  • Burning of cooking gas.
  • Phosphorus burns in air at room temperature.
  • Ignition of a cracker.
Which of the following examples represents explosion?
  • Burning of matchstick
  • Burning of cooking gas
  • Ignition of a cracker
  • Burning of phosphorus in air at room temperature
Explosion of crackers takes place due to application of _________ on them.
  • temperature
  • pressure
  • heat
  • none of these
When fuel is added to the exhaust (burnt) gases in a jet engine combustion takes place. Some facts are mentioned here about this combustion. Pick the false one?
  • It increases the intake of oxygen from the air
  • It reduces fuel consumption
  • It gives additional thrust
  • It is known as 'after burning'
A physical process in which a substance reacts with oxygen to give off heat is called combustion.
  • True
  • False
A white solid $$X$$ reacts with dil.$$HCl$$ to give colourless gas which is used in fire extinguishers. The solid $$X$$ is:
  • $$NaCl$$
  • $$CH_3COONa$$
  • $$Na_2CO_3$$
  • $$NaHCO_3$$
If butane on combustion gives carbon monoxide, find the number of $$O_ 2$$ molecules required.
  • 6
  • 5.5
  • 4.5
  • 4
Gobar gas contains mainly:
  • methane
  • ethane
  • butane
  • carbon monoxide
If you watch a burning candle carefully, you will find different colurs in the flame. Which is the hottest part of the candle flame?
  • The middle orange part
  • The middle, yellow part
  • The outermost portion that is blue
  • The innermost black zone
State true or false.
Combustion can take place at all temperatures less than an ignition temperature.
  • True
  • False

 The heat liberated per kilogram of a fuel is called its:
  • calorific value
  • mass value
  • weight value
  • fuel value
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