Match Column I with Column II and select the correct option from the codes given below. Column I Column II (a) Hottest zone of a candle flame (i) Zone of unburnt wax vapours (b) Yellow zone of a candle flame (ii) Non-luminous zone (c) Black innermost zone of the candle flame (iii) Incomplete combustion zone

(a) - (i), (b) - (ii), (c) - (iii)

(a) - (ii), (b) - (i), (c) - (iii)

(a) - (i), (b) - (iii), (c) - (ii)

MCQ Questions for Class 8 Chemistry Combustion And Flame Quiz 5

The blue zone in a LPG flame indicates _________.

0%
unburnt vapours
0%
partial decomposition
0%
moderately hot
0%
hottest and complete combustion

Which is the hottest part of Bunsen flame?

0%
In the blue zone
0%
Just above the tip of the primary flame
0%
At the top of the outer core
0%
Just above the inner core

Explanation

The hottest part of the bunsen flame is just above the tip of the primary flame. It reaches about

$1500^oC$ .

This is the blue part of the bunsen flame, where the flame has the most oxygen.
Option

$B$ is correct.

Choose the correct statement among the following.

0%
The substances which vapourise during burning, do not give flames.
0%
The substances which have very high ignition temperature are called inflammable substances.
0%
When the matchstick is struck against the rubbing surface, some red phosphorous gets converted into white phosphorous.
0%
The job of a fire extinguisher is to cut off the supply of carbon dioxide, and hence the fire is controlled.

Match Column I with Column II and select the correct option from the codes given below.

	Column I		Column II
(a)	Hottest zone of a candle flame	(i)	Zone of unburnt wax vapours
(b)	Yellow zone of a candle flame	(ii)	Non-luminous zone
(c)	Black innermost zone of the candle flame	(iii)	Incomplete combustion zone

0%
(a) - (i), (b) - (ii), (c) - (iii)
0%
(a) - (ii), (b) - (i), (c) - (iii)
0%
(a) - (i), (b) - (iii), (c) - (ii)
0%
(a) - (ii), (b) - (iii), (c) - (i)

Explanation

Candle flame has three zones as shown in figure.

The first zone is called an outer zone, the second zone is called the middle zone and the third is called the inner zone.

Due to complete combustion, the outer zone is blue in colour and therefore hottest zone.
The middle part is the partial combustion zone and is yellow in colour and this part is moderately hot.
Whereas the inner zone is called a dark zone which has the least unburnt vapours and thus is black in colour.

Depending upon the above explanation

The correct match is:- (a) - (ii), (b) - (iii), (c) - (i)
Hottest zone of candle flame

$\rightarrow$ Non-luminous zone.
Yellow zone of candle flame

$\rightarrow$ Incomplete combustion zone.
Black innermost zone of the candle flame

$\rightarrow$ Zone of unburnt wax vapours.

The combustion in which a material bursts into flames without the application of heat is known as :

0%
complete combustion
0%
spontaneous combustion
0%
slow combustion
0%
none of these

Explanation

The type of combustion in which a material suddenly bursts into flames, without the application of heat or any apparent cause is called spontaneous combustion.

Option

$B$ is correct.

Coal, petroleum, natural gas and propane are fossil fuels. They are called fossil fuels because ________.

0%
they are burnt to release energy and they cause air pollution.
0%
they were formed from the buried remains of plants and tiny animals that lived hundreds of millions of years ago.
0%
they are non renewable and will run out.
0%
they are mixed with fossils to provide energy.

One of the phenomenon which cannot be described as combustion is:

0%
oxidation of coal in air
0%
burning of magnesium in nitrogen
0%
reaction of antimony in chlorine
0%
lighting of an electric lamp

In photosynthesis in plants,

${H}_{2}O$ and

${CO}_{2}$ react in presence of light and chlorophyll to give carbohydrate and oxygen. When the carbohydrate is burnt in air, the gases produced are:

0%
${CO}_{2}+{H}_{2}$
0%
${CO}_{2}+CO$
0%
${CO}_{2}+{H}_{2}O$
0%
${CO}_{2}+{O}_{2}$

Explanation

The carbohydrate is glucose. The combustion of glucose is as follows:

$C_6H_{12}O_6 + 6O_2 \rightarrow 6 H_2O + 6CO_2 + heat$

Combustion occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide, water and energy. This is simply the process of metabolism.

Which of the following diagrams shows a non-luminous flame?

0%
I only
0%
II only
0%
I and II
0%
II and IV

When a burning candle is covered with a glass it extinguishes because:

0%
supply of oxygen is cut off
0%
supply of hydrogen is cut off
0%
supply of nitrogen is cut off
0%
supply of $CO_2$ is cut off

There are holes below the chimney of an oil lamp:

0%
to supply oxygen for burning the oil
0%
to let the smoke escape
0%
to increase the brightness of the lamp
0%
None of these

Explanation

Oxygen is a supporter of combustion. In its absence, the oil cannot burn. So, holes are provided at the bottom of the lamp to ensure a continuous supply of oxygen to allow the oil to burn.

Hence, option

$A$ is correct.

The characteristic(s) of a ideal fuel is(are):

0%
it should release a large amount of energy
0%
it should burn moderately in air
0%
it should be easily transported
0%
all of the above

Which among the following has the highest calorific value?

0%
Petrol
0%
Cow dung cake
0%
Coal
0%
Wood

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?

0%
The outer zone is least hot
0%
The middle zone is hottest
0%
The inner zone is least hot
0%
All the zones have same temperature

Explanation

The hottest part of the flame is the outer zone with blue color which has the highest temperature due to complete combustion, the yellow part of the flame has a temperature less than the outer part.

While the innermost zone is black in color which has the least temperature. This black color is due to unburnt wax vapors. So as the distance of the flame from the centerline increases the temperature increases.

Hence, option

$C$ is correct.

Which of the following is combustible?

0%
Oxygen
0%
Carbon dioxide
0%
Hydrogen
0%
All of the above

Which of the following is a supporter of combustion?

0%
Cooking gas
0%
Nitrogen gas
0%
Oxygen gas
0%
Producer gas

Which of the following flames is produced by a candle?

0%
Green flame
0%
Non-luminous flame(blue)
0%
Light giving flame
0%
Yellow luminous flame

Explanation

There are two types of flame that is produced by candle:

(a) Luminous flame (b) Non-luminous flame

Non-luminous flame is a result of complete combustion and is blue in colour.

Luminous flame is a result of incomplete combustion and is yellow bright in colour.

Hence option

$B$ and

$D$ are correct.

Quality that is not suitable for a fuel is ________ .

0%
high calorific value with ignition temperature that is well above the normal room temperature
0%
low rate of evaporation at room temperature
0%
carbon particles are expelled with smoke
0%
low content of non-combustibles

The lowest temperature at which a combustible substance catches fire is called:

0%
critical temperature
0%
absolute temperature
0%
ignition temperature
0%
none of these

State true or false.

Fossils are present in metamorphic rocks.

0%
True
0%
False

Explanation

$\text{False}$

Metamorphic rocks such as marble are formed by tremendous heat and pressure and fossils can not be found in such places. They are usually found in Sedimentary rocks as these rocks have formed at low temperatures and pressure and suitable for fossils.

______ is the extinguisher used for inflammable material like petrol.

0%
Water
0%
$CO_2$
0%
Oil
0%
Dry powder

Explanation

Some Class-B fires (hydrocarbons, petroleums, and fuels on fire) cannot be efficiently controlled with water.

$CO_2$ being heavier than oxygen covers the fire like a blanket. Hence, one of the important factor for fire is cut off and the fire is controlled.

Nitrogen is a component of air that does not support combustion.

0%
True
0%
False

Explanation

Nitrogen gas is not highly reactive i.e does not support combustion with other molecules in the atmosphere and is mainly present in the air as

$N_2$ (

$78 \%$ ). Unreactive behavior results from the powerful triple bonds that form between the three pairs of electrons shared between two nitrogen atoms. These bonds have relatively short radii, which requires more energy to break. Nitrogen becomes more reactive at higher temperatures. One common nitrogen-based reaction that occurs in the atmosphere is the formation of nitrogen oxide (

$NO$ ), during storms when lightning strikes.

Oxygen is the component of air that supports combustion.

0%
True
0%
False

Ideal fuel has a __________ calorific value.

0%
low
0%
high
0%
moderate
0%
zero

Carbon dioxide is used in fire extinguisher.

0%
True
0%
False

Explanation

Carbon dioxide is used in fire extinguisher, the release of gas under pressure has a cooling effect.

$Na_2CO_3 + H_2SO_4 \rightarrow Na_2SO_4 + H_2O + CO_2$ In the inner part of the extinguisher, the whole container is filled with the strong solution of sodium carbonate and there is a glass tube in the bottom of the container contains sulfuric acid. The glass tube is broken with a powerful pressure when required. And the solutions are reacted with each other and carbon dioxide is produced. Then the

$CO_2$ is released through the tiny hole in a very high pressure and extinguishes the fire.

Carbon dioxide is neither combustible nor a supporter of combustion.

0%
True
0%
False

Explanation

Carbon dioxide is neither combustible nor a supporter of combustion, as

$CO_2$ is an oxide of carbon a stable bonding of one carbon atom with

$2$ oxygen atoms i.e it is already oxidized. in fact, it is used as a fire extinguisher.

Which of the following has lower ignition temperature?

0%
Wood
0%
Paper
0%
Vegetable oil
0%
Kerosene oil

Oxygen supports combustion and is used up in burning.

0%
True
0%
False

Charcoal burns in air to produce ______.

0%
$CO_2$
0%
$H_2O$
0%
$H_2$
0%
$O_2$

Explanation

Charcoal burns in air mainly to produce

$CO_2$ . It usually burns slowly giving an orange glow from the burning layer of charcoal and leaving white ash behind.

A candle burns in a jar of oxygen but is extinguished in nitrogen.

0%
True
0%
False

CBSE Questions for Class 8 Chemistry Combustion And Flame Quiz 5 - MCQExams.com

0:0:1

Practice Class 8 Chemistry Quiz Questions and Answers

CBSE Questions for Class 8 Chemistry Combustion And Flame Quiz 5 - MCQExams.com

0:0:1

Practice Class 8 Chemistry Quiz Questions and Answers

Support mcqexams.com by disabling your adblocker.