SMART EDUCATIONS (www.smarteducations.org) 1
CARBON AND ITS COMPOUNDS
Q. What is carbon?
Ans. Carbon is an element which is catogerized as a non metal. Its symbol
is ‘C’. Its atomic number is 6 because it has 6 protons and hence 6
electrons. Its electronic configuration is (2,4) and hence it has 4 valence
electrons and valency is also 4. It has two isotopes- (i) and (ii) .
6
12
𝐶
6
14
𝐶
Apart from this it has three allotropes :- Graphite, Diamond and
Buckminsterfullerene(C-60).
Q. Why do Graphite, Diamond and Buckminsterfullerene(C-60) have
different physical properties in spite of being made of the same atoms?
Ans. All three have different physical properties because of the different
structure and bonding between the carbon atoms.
In diamond, each carbon atom is bonded to four other carbon atoms
forming a rigid three-dimensional structure.
In graphite, each carbon atom is bonded to three other carbon atoms
in the same plane giving a hexagonal array. One of these bonds is a
double-bond, and thus the valency of carbon is satisfied. Graphite structure
is formed by the hexagonal arrays being placed in layers one above the
other.
In C-60 carbon atoms are arranged in the shape of a football.
Q. Why is carbon neither able to lose 4e
-
to form C
4+
nor to gain 4e
-
to form
C
4-
?
Ans. Carbon is neither able to lose 4e
-
to form C
4+
nor to gain 4e
-
to form
C
4-
:
● Losing electrons: It would require a large amount of energy to remove
four electrons from a carbon atom. This is because of its small size.
● Gaining electrons: It would be difficult for six protons to hold on to ten
electrons. This is also because of its small size.
Q. How does carbon attain the configuration of its nearest noble gases?
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Ans. Carbon attains the configuration of its nearest noble gases by the
sharing of 4 electrons and forms covalent compounds.
Q. What is a covalent compound?
Ans. The compound formed by the sharing of electrons between
nonmetals is known as covalent compound.
Q. What are the differences between ionic compound and covalent
compound?
Ans.
Ionic Compound
Covalent Compound
It is formed by the transfer of
electrons from a metal to a
nonmetal.
It is formed by the sharing of
electrons between nonmetals.
It has ions.
It has no ion.
It is found in solid state.
It is found in solid, liquid and gas
states.
It has a high melting and high
boiling point.
It has a low melting and low boiling
point.
In molten or aqueous state, it
conducts electricity.
It does not conduct electricity.
It is quite stable.
It is less stable.
Q. Why is the compound formed by the carbon more stable than of other
nonmetals?
Ans. Carbon has only two shells so it is small in size and its nucleus is very
close to its outermost shell and this is the reason that it holds the shared
electrons very strongly and thus forms more stable compounds.
Q. Explain the formation of H
2
, O
2
and N
2
.
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Ans. Hydrogen has one electron in its outermost shell so it needs 1 more
electron to attain the configuration of noble gas. Hydrogen does it by
sharing one electron to itself and form H
2
.
In H
2
one electron is shared so it is called a single covalent bond which is
also represented by a line between the two atoms like H - H.
Oxygen has 6 electrons in its outermost shell so it needs 2 more electrons
to attain the configuration of noble gas. Oxygen does it by sharing 2
electrons to itself and forming O
2
.
In O
2
2 electrons are shared so it is called a double covalent bond which is
also represented by a double line between the two atoms like O = O.
Nitrogen has 5 electrons in its outermost shell so it needs 3 more electrons
to attain the configuration of noble gas. Nitrogen does it by sharing 3
electrons to itself and form N
2
.
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In N
2
3 electrons are shared so it is called a triple covalent bond which is
also represented by a triple line between the two atoms like N N.
≡
Q. What would be the electron dot structure of carbon dioxide which has
the formula CO
2
?
Ans.
Q. What would be the electron dot structure of a molecule of sulphur which
is made up of eight atoms of sulphur?
Ans. Sulphur = (2,8,6)
Q. Why does carbon form a large number of compounds?
Ans. The two characteristic features seen in carbon, that is, tetravalency
and catenation, put together give rise to a large number of compounds.
Q. What does catenation mean?
Ans. Carbon has the unique ability to form bonds with other atoms of
carbon, giving rise to large molecules. This property is called catenation.
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These compounds may have long chains of carbon, branched chains
of carbon or even carbon atoms arranged in rings. In addition, carbon
atoms may be linked by single, double or triple bonds.
Q. What does tetravalency mean?
Ans. Since carbon has a valency of four, it is capable of bonding with four
other atoms of carbon or atoms of some other mono-valent element. This
property is called tetravalency.
Q. What does saturated compounds mean?
Ans. Compounds of carbon, which are linked by only single bonds between
the carbon atoms, are called saturated compounds.
Q. What does unsaturated compounds mean?
Ans. Compounds of carbon having double or triple bonds between their
carbon atoms are called unsaturated compounds.
Q. What does hydrocarbon mean?
Ans. The compounds formed by only hydrogen and carbon, are known as
hydrocarbons. There are three types of hydrocarbons:- Alkane, Alkene and
Alkyne.
Q. What does alkane mean?
Ans. The hydrocarbons in which every two carbon atoms are linked by only
single bonds, are known as alkane. The general formula of alkane is
C
n
H
2n+2
, where n is the number of carbon atoms.
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Q. What does alkene mean?
Ans. The hydrocarbons in which any two carbon atoms are linked by
double bonds, are known as alkene. The general formula of alkene is C
n
H
2n
, where n is the number of carbon atoms.
Q. What does alkyne mean?
Ans. The hydrocarbons in which any two carbon atoms are linked by triple
bonds, are known as alkyne. The general formula of alkyne is C
n
H
2n-2
,
where n is the number of carbon atoms.
Q. How does a hydrocarbon get its name?
Ans. Hydrocarbons are named using some rules based on the number of
carbon atoms and the number of bonds between them, for example:-
Rules based on the number of carbon atoms:-
● Meth for 1 Carbon
● Eth for 2 carbons
● Prop for 2 carbons
● But for 2 carbons
● Pent for 2 carbons
● Hex for 2 carbons
Rules based on the number of bonds between carbon atoms:-
● ‘ane’ for single bonds.
● ‘ene’ for double bonds.
● ‘yne’ for triple bonds.
For example:-
Because it has 5 carbons, its name should
start from ‘Pent’ and all carbon atoms are
linked with single bonds, so its name should
end with ‘ane’. So basically its name is
‘Pentane’.
Because it has 6 carbons, its name should
start from ‘Hex’ and two carbon atoms are
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linked with double bonds, so its name should end with ‘ene’. So basically its
name is ‘Hexene’.
Q. Name the following hydrocarbons:-
(a) C
4
H
10
(b) C
2
H
4
(c) C
5
H
8
(d) CH
4
(e) C
3
H
6
(f) C
6
H
10
Ans.
(a) C
4
H
10
= But + ane = Butane
(b) C
2
H
4
= Eth + ene = Ethene
(c) C
5
H
8
= Pent + yne = Pentyne
(d) CH
4
= Meth + ane = Methane
(e) C
3
H
6
= Prop + ene = Propene
(f) C
6
H
10
= Hex + yne = Hexyne
Q. Draw the structure of the following hydrocarbons:-
(a) C
4
H
8
(b) C
2
H
6
(c) C
5
H
10
(d) CH
4
(e) C
4
H
6
(f) C
5
H
8
Ans.
(a) C
4
H
8
(b) C
2
H
6
(c) C
5
H
10
(d) CH
4
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(e) C
4
H
6
(f) C
5
H
8
Q. What does isomer mean?
Ans. The carbon compounds with identical molecular formula but different
structures and properties are called structural isomers and the
phenomenon is called isomerism. For example butane(C
4
H
10
) has two
isomers:-
Q. What is the formula of Benzene and its structure?
Ans. Chemical formula of Benzene is C
6
H
6
and its structure is :-
Q. What does heteroatoms mean?
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Ans. In a hydrocarbon chain, one or more hydrogens can be replaced by
some elements, such that the valency of carbon remains satisfied. In such
compounds, the element replacing hydrogen is referred to as a heteroatom.
Q. What does functional group mean?
Ans. Functional group is a group of atoms that determines the chemical
properties of a carbonic compound regardless of the length and nature of
the carbon chain. Examples of some functional groups are :- Halogens,
Alcohol, Aldehyde, Ketone, Carboxylic acid etc.
Q. Write the general formula for the following:-
(a) Halogens (b) Alcohol (c) Aldehyde (d) Ketone (e) Carboxylic acid
Ans.
Alkane
Alkene
Alkyne
Halogens
C
n
H
2n+1
Cl/Br/I
C
n
H
2n-1
Cl/Br/I
C
n
H
2n-3
Cl/Br/I
Alcohol
C
n
H
2n+1
OH
C
n
H
2n-1
OH
C
n
H
2n-3
OH
Aldehyde
C
n-1
H
2n
CHO
C
n-1
H
2n-2
CHO
C
n-1
H
2n-4
CHO
Ketone
CH
3
COC
n-2
H
2n-3
CH
3
COC
n-2
H
2n-5
CH
3
COC
n-2
H
2n-7
Carboxylic acid
C
n-1
H
2n-1
COOH
C
n-1
H
2n-3
COOH
C
n-1
H
2n-5
COOH
Q. Which heteroatoms are present in the following functional groups?
(a) Halogens (b) Alcohol (c) Aldehyde (d) Ketone (e) Carboxylic acid
Ans.
Functional groups
Heteroatoms
Halogens
Cl/Br/I
Alcohol
OH
Aldehyde
O
Ketone
O
Carboxylic acid
O and OH
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Q. Write down the formula for the following functional groups:-
(a) Halogens (b) Alcohol (c) Aldehyde (d) Ketone (e) Carboxylic acid
Ans.
Functional groups
Formula
Halogens
-Cl/-Br/-I
Alcohol
-OH
Aldehyde
-CHO
Ketone
-CO-
Carboxylic acid
-COOH
Q. Identify the functional group present in the following structure:-
Ans. (a) Alcohol (b) Carboxylic Acid
(c) Ketone (d) Alkyne
Q. Name the following carbonic compounds:-
Ans. (a) C
3
H
7
OH = Prop + ane + ol = Propanol
(b) C
2
H
5
COOH = Prop + ane + oic Acid = Propanoic Acid
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(c) C
2
H
5
COC
2
H
5
= Pent + ane + one = Penatnone
(d) C
4
H
8
= But + ene = Butene
Q. What does Homologous Series mean?
Ans. A series of compounds in which the same functional group substitutes
for hydrogen in a carbon chain and the difference in the chemical formula
between two successive members is CH
2
, is called a homologous series.
For example :- CH
4
, C
2
H
6
, C
3
H
8
etc.
In a homologous series as the molecular formula increases by CH
2
the molecular mass also increases by 14U and a gradation in physical
properties such as increase in melting and boiling are also seen. But as
they have the same functional group, there is no difference in the chemical
properties.
Q. Write down the first member of the following functional groups:-
(a) Halogens (b) Alcohol (c) Aldehyde (d) Ketone (e) Carboxylic acid
(f) Alkane (g) Alkene (h) Alkyne
Ans.
Functional Group
First Member
Halogens
Bromo/Chloro/Iodo - Methane
Alcohol
Methanol
Aldehyde
Methanal
Ketone
Propanone
Carboxylic acid
Methanoic Acid
Alkane
Methane
Alkene
Ethene
Alkyne
Propyne
Q. What does nomenclature mean and what are the rules for the carbonic
compounds?
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Ans. Nomenclature is the set of rules for naming chemical compounds.
Naming a carbon compound can be done by the following method –
1. Identify the number of carbon atoms in the compound.
2. In case a functional group is present, it is indicated in the name of the
compound with either a prefix or a suffix
3. If the name of the functional group is to be given as a suffix, and the
suffix of the functional group begins with a vowel a, e, i, o, u, then the
name of the carbon chain is modified by deleting the final ‘e’ and
adding the appropriate suffix.
4. If the carbon chain is unsaturated, then the final ‘ane’ in the name of
the carbon chain is substituted by ‘ene’ or ‘yne’.
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Q. How many structural isomers can you draw for pentane?
Ans. Three structural isomers can be drawn for pentane.
1. Normal Pentane:-
2. Iso Pentan:-
3. Neo Pentane:-
Q. What are the two properties of carbon which lead to the huge number of
carbon compounds we see around us?
Ans. the two properties of carbon which lead to the huge number of carbon
compounds we see around us are :-
1. Catenation
2. Tetravalency
Q. What will be the formula and electron dot structure of cyclopentane?
Ans. Formula of cyclopentane = C
5
H
10
and its electron dot structure is :-
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Q. Draw the structures for the following compounds.
(i) Ethanoic acid (ii) Bromopentane* (iii) Butanone (iv) Hexanal.
Ans.
(i) Ethanoic acid
(ii) Bromopentane
*Are structural isomers possible for bromopentane?
Ans. Yes, structural isomers of Bromo pentane are possible.
(iii) Butanone
(iv) Hexanal
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Q. How would you name the following compounds?
Ans. (i) Bromo + Eth + ane = Bromoethane
(ii) Meth + an + al = Methanal
(iii) Hex + yne = Hexyne
Q. What are the chemical properties of carbon compounds?
Ans. Following are the chemical properties of carbon compounds:-
1. Combustion:- Most carbon compounds release a large amount of
heat and light on burning (water in the case of hydrocarbon). For
example :-
CH
4
+ O
2
→ CO
2
+ H
2
O + heat and light
C
2
H
5
OH + O
2
→ CO
2
+ H
2
O + heat and light
2. Oxidation:- Conversion of alcohols into carboxylic acids by oxidising
agents, is called oxidation reaction. For example:-
C
2
H
5
OH H
3
COOH
3. Addition Reaction:- Unsaturated hydrocarbons add hydrogen in the
presence of catalysts such as palladium or nickel to give saturated
hydrocarbons. This reaction is known as the Addition Reaction or
Hydrogenation Reaction. For example:-
C
2
H
4
C
2
H
6
4. Substitution Reaction:- In the presence of sunlight, chlorine is
added to hydrocarbons in a very fast reaction. Chlorine can replace
the hydrogen atoms one by one. It is called a substitution reaction
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because one type of atom or a group of atoms takes the place of
another. For example:-
CH
4
+ Cl
2
→ CH
3
Cl + HCl(in the presence of sunlight)
Q. Explain the combustion of saturated hydrocarbons.
Ans. Saturated hydrocarbons will generally give a clean flame(Blue) on
burning and, however, limiting the supply of air results in incomplete
combustion of saturated hydrocarbons giving a sooty flame.
Q. Explain the combustion of unsaturated hydrocarbons.
Ans. Unsaturated hydrocarbons will generally give a sooty flame(Yellow)
and lots of CO
2
on burning.
Q. What does oxidising agents mean?
Ans. Some substances are capable of adding oxygen to others. These
substances are known as oxidising agents. Some examples of oxidising
agents are:- KMnO
4
, K
2
Cr
2
O
7
, CaOCl
2
, HNO
3
etc.
Q. What is the hydrogenation reaction?
Ans. Unsaturated hydrocarbons add hydrogen in the presence of catalysts
such as palladium or nickel to give saturated hydrocarbons. This reaction is
known as the hydrogenation reaction. This reaction is commonly used in
the hydrogenation of vegetable oils using a nickel catalyst.
Vegetable oils generally have long unsaturated carbon chains while
animal fats have saturated carbon chains.
Q. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Ans. Conversion of ethanol to ethanoic acid involves the addition of oxygen
and the removal of Hydrogen, which happens in the case of oxidation
reaction, so the conversion of ethanol to ethanoic acid is also an oxidation
reaction.
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Q. A mixture of oxygen and ethyne is burnt for welding. Can you tell why
a mixture of ethyne and air is not used?
Ans. A mixture of oxygen and ethyne is burnt for welding because in this
process supply of oxygen is sufficient so complete combustion occurs and
lots of heat produced which can melt metals but a mixture of ethyne and air
means insufficient supply of oxygen because air contains only 21% oxygen
so incomplete combustion occur and the produced heat in this way is not
sufficient to melt metals. So a mixture of ethyne and air is not used.
Q. What are the differences between saturated and unsaturated
hydrocarbons?
Ans.
Saturated Hydrocarbon
Unsaturated Hydrocarbon
The carbon atoms are linked with a
single bond.
The carbon atoms are linked with
double or triple bonds.
They are known as alkane.
They are known as alkene or
alkyne.
The general formula is C
n
H
2n+2
The general formula is C
n
H
2n
or
C
n
H
2n-2
They are relatively unreactive.
They are reactive.
It doesn't undergo a hydrogenation
reaction.
It undergoes a hydrogenation
reaction.
On burning, they produce blue
flame and less CO
2
.
On burning, they produce sooty
flame and lots of CO
2
.
In the case of food, they are
unhealthy to eat.
In the case of food, they are healthy
to eat.
Q. What are the physical properties of ethanol?
Ans. Ethanol is a second member of the alcohol functional group and its
chemical formula is C
2
H
5
OH. It is in liquid state at room temperature. It is
commonly called alcohol and is the active ingredient of all alcoholic drinks.
In addition, because it is a good solvent, it is also used in medicines such
SMART EDUCATIONS (www.smarteducations.org) 18
as tincture iodine, cough syrups, and many tonics. Ethanol is also soluble
in water in all proportions. Consumption of small quantities of dilute ethanol
causes drunkenness. However, intake of even a small quantity of pure
ethanol can be lethal.
Q. What are the chemical properties of ethanol?
Ans. Following are the chemical properties of ethanol:-
1. Reaction with Sodium:- Alcohols react with sodium leading to the
evolution of hydrogen and the other product is sodium ethoxide.
2C
2
H
5
OH + 2Na → 2C
2
H
5
ONa + H
2
2. Reaction to give unsaturated hydrocarbon:- Heating ethanol at 443 K
with excess concentrated sulphuric acid results in the dehydration of
ethanol to give ethene.
C
2
H
5
OH C
2
H
4
+ H
2
O
The concentrated sulphuric acid can be regarded as a dehydrating agent
which removes water from ethanol.
Q. What are the physical properties of ethanoic acid?
Ans. Ethanoic acid is the second member of the carboxylic acid functional
group and its chemical formula is CH
3
COOH. It is commonly called acetic
acid. 5-8% solution of acetic acid in water is called vinegar and is used
widely as a preservative in pickles. It is found in liquid state but its freezing
point is very low so it often freezes during winter in cold climates and this
gave rise to its name glacial acetic acid. As its name suggests, it is acidic in
nature but weaker than mineral acids.
Q. What are the chemical properties of ethanoic acid?
Ans. Following are the chemical properties of ethanoic acid:-
1. Reaction between ethanoic acid and ethanol:- Ethanoic acid reacts
with absolute ethanol in the presence of an acid catalyst to give an
ester and the reaction is known as the esterification reaction.
CH
3
COOH + C
2
H
5
OH CH
3
COOC
2
H
5
+ H
2
O
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2. Reaction with base:- Like mineral acids, ethanoic acid reacts with
base such as sodium hydroxide to give a salt known as sodium
ethanoate or commonly called sodium acetate.
CH
3
COOH + NaOH → CH
3
COONa + H
2
O
3. Reaction with carbonates and hydrogen carbonate:- Ethanoic acid
reacts with carbonates and hydrogen carbonates to give rise to salt,
carbon dioxide and water. The salt produced is commonly called
sodium acetate.
2CH
3
COOH + Na
2
CO
3
→ 2CH
3
COONa + CO
2
+ H
2
O
CH
3
COOH + NaHCO
3
→ CH
3
COONa + CO
2
+ H
2
O
Q. What does esterification reaction mean?
Ans. Ethanoic acid reacts with absolute ethanol in the presence of an acid
catalyst to give an ester and the reaction is known as the esterification
reaction. This is a reversible reaction.
CH
3
COOH + C
2
H
5
OH CH
3
COOC
2
H
5
+ H
2
O
Q. What does saponification reaction mean?
Ans. On treating with sodium hydroxide, which is an alkali, the ester is
converted back to alcohol and sodium salt of carboxylic acid. This reaction
is known as saponification because it is used in the preparation of soap.
Q. What is soap?
Ans. Soap is a sodium or potassium salts of long chain carboxylic acid.
Q. What is an ester?
Ans. Ester is a sweet-smelling substance. These are used in making
perfumes and as flavouring agents.
Q. How would you distinguish experimentally between an alcohol and a
carboxylic acid?
Ans. We can distinguish experimentally between an alcohol and a
carboxylic acid in the following ways:-
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1. Using acid-base indicators:- Because carboxylic acid is acidic in
nature and alcohol is neither acidic nor basic so by using acid-base
indicators we can easily distinguish between them.
2. By reacting with Na
2
CO
3
or with NaHCO
3
:- Carboxylic acid produces
CO
2
when it reacts with Na
2
CO
3
or with NaHCO
3
while alcohol does
not react with them.
Q. What is soap?
Ans. Soap is a sodium or potassium salts of long chain carboxylic acid thus
its molecules has two different ends with different properties:-
1. Hydrophilic end:- Hydrophilic means attracted toward water and the
ionic end of the soap has this property so , ionic end is hydrophilic
end.
2. Hydrophobic end :- Hydrophobic means distracted by water and
hence attracted toward oil. Carboxylic end of the soap has this
property so, this end is a hydrophobic end.
Q. What is micelle?
Ans. The clusters of molecules in which the hydrophobic tails are in the
interior of the cluster and the ionic ends are on the surface of the cluster.
This formation is called a micelle.
Q. Explain the action of soap on dirt.
Ans. Most dirt is oily in nature and it does not dissolve in water. When soap
is dissolved in water its hydrophobic ends attach themselves to the dirt and
remove it from the cloth. Then the molecules of soap arrange themselves in
micelle formation and trap the dirt at the centre of the cluster. These
micelles remain suspended in the water.
SMART EDUCATIONS (www.smarteducations.org) 21
Q. What does hard water mean?
Ans. The water which contains high amounts of calcium or magnesium, is
called hard water.
Q. Explain the action of soap in hard water?
Ans. Hard water contains calcium and magnesium salts which react with
the soap molecules and produce an insoluble substance called scum and
hence its cleaning power decreases and doesn’t work well.
Q. How do we overcome the problem of making scum when soap is used in
hard water?
Ans. Soap molecules react with the salts present in hard water and
produce scum which decreases the cleaning power of soap. This problem
is overcome by using another substance called detergents.
Q. What are detergents?
Ans. Detergents are generally sodium salts of sulphonic acids or
ammonium salts with chlorides or bromides ions, etc. Both have long
SMART EDUCATIONS (www.smarteducations.org) 22
hydrocarbon chains. They are usually used to make shampoos and
products for cleaning clothes.
Q. Why does detergent not produce scum in hard water?
Ans. Detergents are generally sodium salts of sulphonic acids or
ammonium salts with chlorides or bromides ions, etc. Both have long
hydrocarbon chains and these chains do not react with the salts present in
hard water to produce scum.
Q. Would you be able to check if water is hard by using a detergent?
Ans. By using a detergent we would not be able to check if water is hard,
because it works the same in hard water or soft water.
Q. People use a variety of methods to wash clothes. Usually after adding
the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub
with a brush or the mixture is agitated in a washing machine. Why is
agitation necessary to get clean clothes?
Ans. Agitation is necessary to get clean clothes because it removes dirt
particles in the form of micelles from the surface of the cloth.
Exercises
1. Ethane, with the molecular formula C
2
H
6
has
Ans. (b) 7 covalent bonds.
2. Butanone is a four-carbon compound with the functional group
Ans. (c) ketone.
3. While cooking, if the bottom of the vessel is getting blackened on the
outside, it means that
Ans. (b) the fuel is not burning completely.
4. Explain the nature of the covalent bond using the bond formation in
CH
3
Cl.
Ans.
SMART EDUCATIONS (www.smarteducations.org) 23
Bond formation in CH
3
Cl Carbon forms a single
covalent bond by sharing one electron pair with three hydrogen atoms and
one chlorine atom. Chlorine being more electronegative adds polar nature
to the C—Cl bond.
5. Draw the electron dot structures for
(a) ethanoic acid.
Ans.
(b) H
2
S.
Ans.
(c) propanone.
Ans.
(d) F
2
Ans.
SMART EDUCATIONS (www.smarteducations.org) 24
6. What is an homologous series? Explain with an example.
Ans. A series of compounds in which the same functional group substitutes
for hydrogen in a carbon chain and the difference in the chemical formula
between two successive members is CH
2
, is called a homologous series.
For example :- CH
4
, C
2
H
6
, C
3
H
8
etc.
7. How can ethanol and ethanoic acid be differentiated on the basis of
their physical and chemical properties?
Ans. Differences in physical properties between ethanol and ethanoic
acid:-
Ethanol
Ethanoic acid
It has a burning taste.
It has a sour taste.
It does not freeze in the winter
season.
It freezes in the winter season.
It has a pleasant smell.
It has a vinegar-like smell.
Differences in chemical properties between ethanol and ethanoic acid:-
Ethanol
Ethanoic acid
It does not change the color of
litmus paper.
It changes the color of blue litmus
paper to red.
It does not react with metal
carbonate or metal hydrogen
carbonate.
It reacts with metal carbonate or
metal hydrogen carbonate to give
salt, CO
2
and H
2
O.
It can be oxidised to give ethanoic
acid.
It cannot be oxidised.
SMART EDUCATIONS (www.smarteducations.org) 25
8. Why does micelle formation take place when soap is added to water?
Will a micelle be formed in other solvents such as ethanol also?
Ans. When soap is added to water, micelle formation takes place.
This is because the hydrocarbon chains of soap molecules are hydrophobic
which are insoluble in water, but the ionic ends of soap molecules are
hydrophilic and hence soluble in water.
Formation of micelle will not occur in solvents such as ethanol
because the both ends of the soap molecules almost dissolve in ethanol.
9. Why are carbon and its compounds used as fuels for most
applications?
Ans. Carbon and its compounds are used as fuels for most
applications because they have several properties that make them a good
source of energy:
● Produce a lot of heat and light: When carbon is burned in air, it
releases a large amount of heat and light in the form of carbon
dioxide.
● Burn with a clean flame: Saturated hydrocarbons burn with a clean
flame and produce no smoke.
● High calorific values: Carbon compounds have high calorific values,
meaning they produce a lot of heat when burned.
● Optimum ignition temperature: Carbon compounds have an optimum
ignition temperature, meaning they ignite easily.
● Easy to handle: Carbon compounds are easy to handle.
● Combustion can be controlled: The combustion of carbon compounds
can be controlled.
10. Explain the formation of scum when hard water is treated with
soap.
Ans. Hard water contains calcium and magnesium salts. When soap
is added to hard water, the calcium and magnesium ions in the water
displace the sodium or potassium ions from the soap molecules. This forms
an insoluble substance called scum.
SMART EDUCATIONS (www.smarteducations.org) 26
11. What change will you observe if you test soap with litmus paper
(red and blue)?
Ans. Because soap is basic in nature hence it changes the color of
red litmus paper to blue but does not change the color of blue litmus paper.
12. What is hydrogenation? What is its industrial application?
Ans. Hydrogenation is a chemical reaction that adds hydrogen to
unsaturated hydrocarbons in the presence of a catalyst to create saturated
hydrocarbons. It has many industrial applications, including:
Hydrogenation is used to convert vegetable oils into ghee and it is used to
preserve or purify many products.
13. Which of the following hydrocarbons undergo addition reactions:
C
2
H
6
, C
3
H
8
, C
3
H
6
, C
2
H
2
and CH
4
.
Ans. Only C
2
H
2
and C
3
H
6
undergo addition reactions out of the given
hydrocarbons C2H6, C3H8, C3H6, C2H2, and CH4:
Because only unsaturated hydrocarbons undergo addition reactions.
14. Give a test that can be used to differentiate between saturated and
unsaturated hydrocarbons.
Ans. When saturated hydrocarbons are burnt in the presence of
sufficient supply of oxygen, it gives blue flame while in the case of
unsaturated hydrocarbons, it gives a sooty(yellowish) flame.
15. Explain the mechanism of the cleaning action of soaps.
Ans. Soaps work by attaching to dirt and removing it from clothing or
skin through a process that involves the following steps:
● Dissolution: Soap is dissolved in water.
● Attachment: The hydrophobic ends of the soap attach to the
dirt. The hydrophilic part of the soap remains in contact with the
water molecules.
● Micelle formation: The soap molecules form micelles, trapping
the dirt in the center.
● Suspension: The micelles remain suspended in the water.
● Rinsing: The trapped dirt can be easily rinsed off.
