9.
202
Amazing World of
Carbon Compounds
SCHOOL SECTION
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Q.I
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
*16.
17.
18.
19.
20.
21.
*22.
*23.
*24.
*25.
*26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
SCIENCE & TECHNOLOGY
EDUCARE LTD.
(A) Fill in the blanks :
The number of valence electrons in carbon are ....................... .
The property of direct bonding between atoms of the same element to form
chain is known as ....................... .
In saturated hydrocarbons two carbon atoms are linked by ....................... .
....................... is an alkyne.
Ethene has ....................... .
The molecular mass of two adjacent members in homologous series of
alkane differs by ....................... .
....................... is the first member of alkane family.
There are ....................... carbon atoms in butane.
....................... gas is called marsh gas.
....................... is first homolog of alkene series.
Vinegar is ....................... .
Molecular formula of benzene is ....................... .
In the earlier days, the compounds obtained from animal or plant kingdom
were called as ....................... .
Atomic number of carbon is ....................... .
An organic compound containing only carbon and hydrogen elements is
called ....................... .
General molecular formula of alkane is ....................... .
Molecular formula of ethane is ....................... .
The general molecular formula of alkene is ....................... .
Hydrocarbons in which two carbon atoms are linked by triple bond is called
....................... .
The general formula for alkyne is ....................... .
Organic compounds with same general molecular formula are known as
....................... .
The organic compounds having double or triple bond in them are termed as
....................... .
....................... are known as parent organic compound.
Covalent compounds are generally soluble in ....................... solvents.
Triple bond can be obtained by sharing ....................... pairs or .......................
electrons.
Hydrocarbons necessarily contain ....................... and ....................... .
Methane is also called ....................... .
The electronic configuration of carbon is ....................... .
Carbon has ....................... electrons in its outermost orbit, hence it is
....................... .
Bond formed by sharing of electrons are known as ....................... .
All hydrocarbons burn in air to form ....................... and ....................... .
Ethanol is called ....................... or ....................... .
Ethanol has a formula ....................... .
When sodium comes in contact with ethyl alcohol it gives .......................
gas.
Ethanoic acid is commonly known as ....................... acid.
Acetic acid has the formula ....................... .
Below 290k acetic acid solidifies to an ice like mass called ....................... .
Answers :
1. 4
3. single bond
5. double bond
7. Methane
SCHOOL SECTION
2.
4.
6.
8.
catenation
Ethyne
14
4
203
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SCIENCE & TECHNOLOGY
9.
11.
13.
15.
17.
19.
21.
23.
25.
27.
29.
31.
33.
35.
37.
Methane
acetic acid
organic compounds.
hydrocarbon.
C 2H 4
alkyne
homolog
Hydrocarbon
3, 6
marsh gas
4, tetravalent
CO2, H2O
C 2H 5OH
acetic acid
glacial acetic acid
Q.I
1.
(i)
(ii)
(iii)
(B) Match the following :
Column I
Alkanes
Alkenes
Alkynes
Ans.
2.
(i)
(ii)
(iii)
(iv)
Ans.

•
•
•
•
Q.I
1.
Ans.
2.
Ans.
3.
Ans.
4.
Ans.
204
10.
12.
14.
16.
18.
20.
22.
24.
26.
28.
30.
32.
34.
36.
Ethene
C 6H 6
6
CnH2n + 2
C nH 2n
CnH2n - 2
unsatured hydrocarbon
organic
hydrogen, carbon
2, 4
covalent bond
ethyl alcohol, spirit
hydrogen
C 2H4O 2
(a)
(b)
(c)
(d)
Column II
C nH 2n
CnH2n + 2
C 2H4O 2
CnH2n – 2
(a)
(b)
(c)
(d)
(e)
Column II
Green house gas
C 6H 6
Unsaturated hydrocarbon
C 2H 6
C 4 H 10
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(i - b), (ii - a), (iii - d).
Column I
Benzene
Butane
Methane
Propene
(i - b), (ii - e), (iii - a), (iv - c).
MEMORISE :
Isotopes of carbon : The most common isotope of carbon, carbon-12, was
adopted in 1961 as the standard for atomic weights and was assigned
weight of 12.
Carbon 12 accounts for almost 99% of naturally occurring carbon.
Carbon 13 accounts for most of the rest.
Carbon 14, a radioactive isotope, occurs only in traces. It is used by
scientists in determining the age of prehistoric objects.
– Extra Information.
(C) State whether the following statements are true or false. If false
write the corrected statement :
Study of organic compounds is called organic chemistry.
True.
Hydrocarbons are the compounds containing carbon and hydrogen elements
only.
True.
Hydrocarbons with double bond are called saturated hydrocarbons.
False. Hydrocarbons with single bond are called saturated hydrocarbons.
Ethylene contains carbon carbon triple bond.
False. Ethylene contains carbon-carbon double bond.
SCHOOL SECTION
MT
5.
Ans.
6.
Ans.
7.
Ans.
8.
Ans.
9.
Ans.
10.
Ans.
Q.I
1.
Ans.
SCIENCE & TECHNOLOGY
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Ethene is an unsaturated hydrocarbon.
True.
Propyne is an alkene.
False. Propyne is an alkyne.
The formula of each homolog series differs from the member above or
below it by one CH2 group.
True.
General formula of alkane is CnH2n.
False. General formula of alkane is CnH2n + 2.
The molecular formula of propane is C3H6.
False. The molecular formula of propane is C3H8.
Ethane is the first member of alkane family.
False. Methane is the first member of alkane family.
2.
Ans.
3.
Ans.
(D) Find the odd man out :
Sugar, Common salt, Cotton, Detergents.
Common salt. It is an inorganic compound while the rest are organic
compounds.
Methane, Ethane, Ethene, Butane.
Ethene. It is an alkene while the rest are alkanes.
Hydrochloric acid, Sulphuric acid, Acetic acid, Nitric acid.
Acetic acid. It is an organic acid while the rest are inorganic acids.
Q.I
1.
Ans.
2.
Ans.
3.
Ans.
4.
Ans.
(E) Write the correlated terms :
Alkane : CnH2n + 2 :: Alkynes : ................. .
CnH2n – 2
Propene : Double bond :: Propyne : ................. .
Triple bond
Ethane : C2H6 :: Benzene : ................. .
C6H 6
Ethane : CH3 - CH3 :: Ethene : ................. .
CH2 == CH2
Q.I
1.
Ans.
(F) Write molecular formula and structural formula of the following :
Methane.
Molecular formula : CH 4
Structural formula :
2.
Ans.
H
|
H —— C —— H
|
H
Ethane.
Molecular formula : C2H6
Structural formula :
SCHOOL SECTION
H
H
|
|
H —— C —— C —— H
|
|
H
H
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SCIENCE & TECHNOLOGY
3.
Ans.
Propane.
Molecular formula : C3H8
Structural formula :
4.
Ans.
H
H
|
|
H —— C === C —— H
Ethyne.
Molecular formula : C2H2
Structural formula :
7.
Ans.
H
H
H
H
|
|
|
|
H —— C —— C —— C —— C —— H
|
|
|
|
H
H
H
H
Ethene.
Molecular formula : C2H4
Structural formula :
*6.
Ans.
H
H
H
|
|
|
H —— C —— C —— C —— H
|
|
|
H
H
H
Butane.
Molecular formula : C4H10
Structural formula :
5.
Ans.
EDUCARE LTD.
H —— C  C —— H
Benzene.
Molecular formula : C6H6
H
|
C
Structural formula :
H —— C
|
|
H —— C
C —— H
||
||
C —— H
C
|
H
8.
Ans.
Acetic acid.
Molecular formula :
Structural formula :
9.
Ans.
Heptane.
Molecular formula :
Structural formula :
206
CH3COOH
H
OH
|
|
H —— C —— C = O
|
H
C7H16
H
H
H
H
H
H
H
|
|
|
|
|
|
|
H——C——C——C——C ——C——C ——C——H
|
|
|
|
|
|
|
H
H
H
H
H
H
H
SCHOOL SECTION
MT
10.
Ans.
SCIENCE & TECHNOLOGY
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Cyclohexane.
Molecular formula :
C6H12
H
H
H
H
C
Structural formula :
H
H
H
C
C
|
|
|
|
C
C
C
H
11.
Ans.
Ethanol.
Molecular formula :
Structural formula :
12.
*2.
Ans.
*3.
Ans.
*4.
Ans.
5.
Ans.
6.
Ans.
7.
Ans.
H
H
H
C2H5OH
H
H
|
|
H —— C —— C —— OH
|
|
H
H
Electron. (Dot and cross structure of methane)
Ans.
Q.II
1.
Ans.
H
H
.
×
H . ×C× . H
×
.
H
.
×
Electrons of hydrogen
Electrons of carbon
Define the following :
Organic chemistry.
Study of organic compounds is called organic chemistry.
Also, the branch of chemistry dealing with carbon compounds, other than
carbon monoxide, carbon dioxide and carbonates is called organic chemistry.
Catenation.
The property of direct bonding between atoms of the same element to form
chain is called catenation.
Hydrocarbons.
Hydrocarbons are the compounds containing carbon and hydrogen elements
only.
Saturated hydrocarbon.
A hydrocarbon in which the carbon atoms are linked to each other only by
single covalent bond is called saturated hydrocarbon or alkanes or paraffins.
Unsaturated hydrocarbons.
Hydrocarbons in which carbon atoms are linked to each other by double or
triple covalent bonds are known as unsaturated hydrocarbons.
Alkane.
Hydrocarbon containing only single carbon-carbon bonds are called alkane.
Alkene.
Hydrocarbons containing double bonds between carbon atoms are called
as alkene.
SCHOOL SECTION
207
SCIENCE & TECHNOLOGY
8.
Ans.
9.
Ans.
10.
Ans.
11.
Ans.
12.
Ans.
13.
Ans.
14.
Ans.
15.
Ans.
MT
EDUCARE LTD.
Alkyne.
Hydrocarbons containing triple bonds between carbon atoms are called as
alkyne.
Allotropy.
The phenomenon of existance of a substance in various physical forms but
same chemical form is known as allotropy.
Isomers.
Compounds with identical molecular formula but different structure are
called isomers.
Isomerism.
Compounds with identical molecular formula but different structure are
called isomers and the property is known as isomerism.
Homologous series.
A group of organic compounds containing same functional group, which
can be represented by the same general formula and which more or less
show similar trends in their properties is known as homologous series.
Functional group.
The atom or group of atoms present in the molecule which determines
characteristic property of organic compounds is called the functional group.
Addition reaction.
The reaction in which two molecules react to form a single product is
known as addition reaction.
Substitution reaction.
Reaction where substitution of one or more atoms in a molecule by another
atom take place are called substitution reaction.
Q.III (A) Give scientific reasons :
1. Methane is called marsh gas.
Ans. 1. Methane is formed by the decomposition of plant and animal matter in
swamps or marshy areas.
2. As methane gas produces, bubbles out of marshy area, it is called as
marsh gas.
2. Ethylene is an unsaturated hydrocarbon.
Ans. 1. A hydrocarbon in which valencies of carbon are not fully satisfied by
single covalent bond is called unsaturated hydrocarbon.
| 
 |
2. They contain carbon to carbon double bonds.  __ C  C __  or triple


bonds ( — C  C — ).
3. Ethylene molecule contains two carbon atoms which are bonded to
each other by a C == C i.e. carbon – carbon double bond.
Hence, ethylene is an unsaturated hydrocarbon.
Q.III (B) Answer the following questions in short :
1. Write the uses of diamond.
Ans. 1. Diamond is used as precious stone.
2. Black diamond is used for cutting glass.
2. Write the uses of graphite.
Ans. 1. Graphite is used as electrodes of carbon.
2. It is used as lubricants
3. It is used in lead pencils.
3. Write the uses of acetic acid.
Ans. 1. The solution of acetic acid in water is called vinegar. (Name derived
from its source ‘vinegar’. Latin : Acetum = Vinegar)
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4.
Ans.
5.
Ans.
6.
Ans.
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2. Vinegar contains 5 to 8% acetic acid and is used as a preservative in
the preparation of pickles, sauces, artificial fibres, dyes and plastics.
Write the physical properties of ethanol.
1. It is a colourless liquid and has pleasant odour.
2. Its boiling point is 78ºC.
3. Its freezing point is –114ºC.
4. It is combustible and burns with blue flame.
5. It is immiscible with water.
Write the physical properties of ethanoic acid (acetic acid).
1. Ethanoic acid is colourless and corrosive liquid.
2. It is a weak acid.
3. It has a pungent smell at ordinary temperature.
4. Below 290k (17ºC) it solidifies to an ice like mass called glacial acetic
acid.
What are hydrocarbons ? Give the classification of hydrocarbons.
Hydrocarbons are the compounds containing carbon and hydrogen elements
only. Hydrocarbons are classified as follows :
Hydrocarbons : Compounds containing carbon and hydrogen only.
Open chain hydrocarbons (Aliphatic)
Saturated hydrocarbons
Definition : Hydrocarbons in which
all the four valencies of carbon atoms
are satisfied by single covalent bonds.
Alkanes
Compounds containing
C - C single bonds
Eg. CH 4 Methane
C 2H 6 Ethane
C 3H 8 Propane
C 4 H 10 Butane
7.
Ans.
Closed-chain
Unsaturated hydrocarbons
Definition : Hydrocarbons in which all
the four valencies of carbon atoms are
not satisfied by single covalent bonds only
i.e. they contain double or triple bonds.
Alkenes
Compounds containing
C = C double bonds
Eg. C 2H 4 Ethene or
Ethylene
C 3H 6 Propene
C 4H 8 Butene
Alkynes
Compounds containing
C C triple bonds
Eg. C 2H 2 Ethyne or
Acetylene
C 3H 4 Propyne
C 4H 6 Butyne
What are closed chain hydrocarbons? Give examples.
1. Closed chain hydrocarbons are the hydrocarbons in which carbon atoms
linked to each other in a ring from thus forming a closed chain a cyclic
or ring structure.
2. Eg. Cyclohexane.
H
H
H
H
C
Structural formula : H
C
C
H
|
|
H
H
|
|
C
C
C
H
SCHOOL SECTION
H
H
H
209
MT
SCIENCE & TECHNOLOGY
8.
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Give the IUPAC name of the following :
1. CH3 – CH2 – CH2 – OH.
Ans.
H
H
H
|
|
|
H —— 3 C —— 2 C —— 1 C —— OH
|
|
|
H
H
H
The structure is
1. One hydrogen atom is substituted by –OH group.
2. In the above compound longest chain is of three carbon atoms. Hence
the name of parent alkane is propane.
3. Since the functional group is alcohol, remove ‘e’ from the word propane
and substitute it with –‘ol’
4. The carbon atom to which the –OH group is attached is numbered as
C1 and other are numbered accordingly.
5. The compound CH3 – CH2 – CH2 – OH is named as propan –1–ol.
2. HCOOH.
Ans.
The structure is
O
||
H –––– C –––– OH
1. In the above compound longest chain is of one carbon atom. Hence the
name of parent alkane is methane.
2. Since the functional group is carboxylic acid remove ‘e’ from the word
methane and substitute ‘oic acid’.
3. The compound HCOOH is named as methanoic acid.
3. CH3COOH.
Ans.
The structure is
H
O
|
||
H –––– C –––– C –––– OH
|
H
1. In the above compound longest chain is of two carbon atom. Hence the
name of parent alkane is ethane.
2. Since the functional group is carboxylic acid remove ‘e’ from the word
ethane and substitute ‘oic acid’.
3. The compound CH3COOH is named as ethanoic acid.
4. CH3CH = CHCH3.
Ans.
*9.
Ans.
210
The structure is
4
CH3 –––– 3CH ==
2
CH –––– 1CH3
1. The longest chain of carbon atoms is four and it is in a straight line.
2. Hence the name of parent alkane is butane but for unsaturated
hydrocarbon, the suffix - ene is added. So the above chain is butene.
Numbering of carbon atom starts from the carbon atom nearest to the
double bond.
3. The position of double bond in the chain is indicated by prefix the lower
number of the carbon atoms between double bonds. Since the double
bond is between C2 and C3 the compound is but–2–ene.
Draw chain and ring structure of organic compound having six carbon
atoms in them.
1. Name of organic compound having six carbon atoms and chain
structure.
Hexane formula
: C6H14
SCHOOL SECTION
MT
Structural formula :
Ans.
SCIENCE & TECHNOLOGY
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H
H
H
H
H
H
|
|
|
|
|
|
H——C——C——C——C——C——C—— H
|
|
|
|
|
|
H
H
H
H
H
H
2. Name of organic compound having six carbon atoms and ring
structure.
Molecular formula :
C6H12 (Cyclohexane formula)
H
H
H
H
C
Structural formula :
H
H
C
C
|
|
|
|
C
C
H
C
H
10.
Ans.
11.
Ans.
12.
Ans.
13.
Ans.
H
H
H
H
What do you understand by substitution reaction ?
Reactions where substitution of one or more atoms in a molecule by another
atom takes place are called substitution reaction.
Eg. : Reaction of chlorine with methane :
UV rays
+ Cl 2 
CH 3Cl + HCl
CH 4

In this reaction H atom of methane is substituted by Cl atom.
Reaction of KOH with CH3CH2I :
  CH3CH2OH +
+ KOH
KI
CH3CH2I

In this reaction I atom is substituted by OH.
Which organic compounds readily undergo addition reactions ? Why ?
The reaction in which two molecules react to form a single product is
known as addition reaction.
Unsaturated organic compounds readily undergo addition reactions as
unsaturated compound contains double or triple bonds. Reactions adds to
carbon atoms of C == C double and C  C triple bond.
Explain the reaction of sodium metal and PCl3 on ethanol.
1. When sodium metal comes in contact with ethanol it liberates hydrogen
gas.
2C 2H5OH
+ Na
 2C 2H5ONa
+ H2 
Ethanol
Sodium metal Sodium ethoxide
Hydrogen gas
2. When ethanol reacts with PCl 3 (Phosphorous trichloride) it forms
ethylchloride.
3C2H5OH
+ PCl 3
 3C 2H5Cl
+ H3PO3 
Ethanol
Ethyl chloride
What is action of chlorine, sodium metal and ethanol with ethanoic
acid ?
1. Ethanoic acid is commonly known as acetic acid, reacts with chlorine
to form mono chloro acetic acid.
CH3COOH
+ Cl 2  CH2ClCOOH
+ HCl
Monochloro acetic acid
Monochloro acetic acid further reacts with chlorine to form dichloro
acetic acid.
CH2ClCOOH
+ Cl 2  CHCl2COOH
+ HCl
Dichloro acetic acid
SCHOOL SECTION
211
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SCIENCE & TECHNOLOGY
14.
Ans.
EDUCARE LTD.
Dichloro acetic acid further reacts with chlorine to form trichloro acetic
acid.
CHCl2COOH
+ Cl 2
 CCl3COOH
+ HCl
Trichloro acetic acid
2. Metal sodium reacts with acetic acid and forms sodium acetate along
with that hydrogen gas is liberated.
+ 2Na
 2CH3COONa
+ H2 
2CH3COOH
Sodium acetate
3. When acetic acid reacts with ethanol in presence of anhydrons ZnCl2,
ethylacetate is formed.
CH3COOH
+ C 2H 5OH CH3COOC2H 5
+ H2O
Ethyl acetate (ester)
How is nitrogen molecule (N2) formed ? Show its electron dot and cross
structure.
1. The electronic configuration of nitrogen is 2, 5. In case of nitrogen, the
atomic number of nitrogen is 7. Hence 5 electrons are present in the
outermost shell and it requires 3 more electrones to complete its octate.
So each nitrogen atom shares its three valence electron with the valence
electrons of another nitrogen atom to give three shared pairs of electrons
which results in the formation of N2 molecule.
2. The structure of N2 molecule :
N   N  N  N  N 2
Q.III (C) Write short notes for the following :
*1. Catenation.
Ans. 1. The property of direct bonding between atoms of the same element to
form chain is called catenation.
2. Carbon atoms possess an unusual capability of bonding to other carbon
atoms.
3. Because of this feature, carbon atoms are capable of forming large
number of compounds.
4. Carbon can link with other carbon atoms to form straight chains or
branched chains or rings of different shapes and sizes.
|
|
|
|
|
—— C —— C —— C —— C —— C ——
|
|
|
|
|
|
|
|
|
—— C —— C —— C —— C ——
|
|
|
|
—— C ——
|
|
|
—— C —— C ——
|
|
—— C —— C ——
|
|
*2.
Ans.
212
Straight chain
Branched chain
Closed chain
(Ring)
Homologous series.
Homologous series – organic compounds :
1. Organic compounds having same general molecular formula, similar
structure with similar chemical properties are placed together in the
same series are called homolog and series of such similar compounds
is called homologous series.
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2. The formula of each homolog differs from the member above or below it
by one – CH2 group.
3. The molecular mass of every two adjacent members differ by 14.
(C = 12; H = 1, – CH2 = 14)
For example homologous series of alkane :
General formula : CnH2n + 2
Values of ‘n’
n
n
n
n
=
=
=
=
Molecular formula Alkane
1
2
3
4
CH 4
C 2H
C 3H 8
C 4 H 10
Molecular mass
Methane
Ethane
Propane
Butane
16
30
44
58
*3. Functional groups.
Ans. 1. The atom or group of atoms present in the molecule which determines
characteristic property of organic compound is called the functional
group.
2. All organic compounds are considered as derivatives of hydrocarbons,
it is formed by replacing one or more hydrogen atom in a molecule by
some other atom.
3. In methane CH4, if one hydrogen is replaced by an –OH group, then
compound methyl alcohol. CH 3.OH is formed. The –OH group is the
alcoholic functional group.
4. After replacement, a new compound has functions i.e. properties
different from the parent hydrocarbon.
Some functional group in carbon compounds.
Type of
compound
Functional
group
R – OH
Compounds containing
functional group
Name
Formula
– OH
Ethyl alcohol
C2H5 – OH
R – CHO
H
|
(–– C = 0)
Acetaldehyde
H
|
CH 3 – C = 0
3. Ketones
O
||
R – C – R
O
||
–– C ––
Acetone
(Dimethyl
ketone)
O
||
CH 3 – C –CH 3
4. Carboxylic
acid
R – COOH
– COOH
Acetic acid
CH3COOH
1. Alcohols
2. Aldehydes
Q.IV
1.
Ans.
General
formula
R = CnH2n + 1
R = alkyl group
(A) Distinguish between :
Diamond and Graphite.
1.
2.
3.
4.
Diamond
It is a hard, beautiful crystalline
substance.
Each carbon atom is linked to
four other neighbouring carbon
atoms.
Shape is regular tetrahedron.
No mobile electrons in the system
and hence it is a non-conductor
of electricity.
SCHOOL SECTION
Graphite
1. It is a soft, grayish black
crystalline substance.
2. Each carbon atom is attached to
three other carbon atoms.
3. Shape is hexagonal planar.
4. Free electrons move throughout
the layers and hence it is a good
conductor of electricity.
213
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*2.
Ans.
Toilet soap amd Laundry soap.
3.
Ans.
Soap and Detergent.
Q.V
1.
Ans.
Answer the following in detail :
Write a short not on : 1. Alkanes 2. Alkenes 3. Alkynes.
1. Introduction of alkanes :
(a) Alkanes : saturated aliphatic hydrocarbons containing a carbon-
Toilet soap
Laundry soap
1. High quality of fats and oils used 1. Cheaper quality of fats and oil are
as raw material.
used.
2. Expensive perfumes added.
2. Cheaper perfumes added.
3. No free alkali content present to 3. Free alkali present for cleaning
prevent injuries to skin.
action.
Soap
Detergent
1. It is a sodium or potassium salt 1. It is a sodium salt of alkyl
of long chain carboxylic acids.
benzene sulphonate or of fatty
alcohol sulphates.
2. A soap is less effective in hard 2. A detergent can change hard
water.
water to soft water.
 |

|
 __ __ __ 
C 
carbon single bond. They contain a  C
covalent bond
|
 |



and (–– C –– H ––) covalent bonds in their molecule.
Saturated hydrocarbons : Since all the four valencies of carbon
atoms are fully satisfied by forming single covalent bonds these
compounds are said to be saturated.
(b) Paraffins : Alkanes are known as paraffins (latin : parum = little;
affinis = affinity). They contain strong C – C and C – H bonds and
hence are relatively chemically inert.
(c) General formula : The general formula of alkanes is CnH2n + 2
(d) Naming of Alkanes : From one to four carbon atoms, the name is
trivial or common name. From five to ten carbon atoms, the name
is derived from Greek language.
214
Number of
Greek name
carbon atoms
One carbon atom
Meth
Two carbon atoms
Eth
Three carbon atoms
Prop
Four carbon atoms
But
Five carbon atoms
Pent
Greek name
Number of
carbon atoms
Six carbon atoms
Hex
Hept
Seven carbon atoms
Oct
Eight carbon atoms
Non
Nine carbon atoms
Dec
Ten carbon atoms
Molecular
formula - CnH2n + 2
Name
Molecular
formula - CnH2n + 2
Common
name
CH 4
C 2H 6
C 3H 8
C 4 H 10
C 5 H 12
Methane
Ethane
Propane
Butane
Pentane
C 6 H 14
C 7 H 16
C 8 H 18
C 9 H 20
C 10 H 22
Hexane
Heptane
Octane
Nonane
Decane
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Structural formula of methane and ethane :
H
|
H — C — H
|
H
Methane (CH4)
2.
H
H
|
|
H — C — C — H
|
|
H
H
Ethane (CH3-CH3)
Introduction of alkenes :
(a) Alkenes : unsaturated aliphatic hydrocarbons containing a carbon |
| 
carbon double bond  __ C  C __  in their molecule.
Unsaturated Hydrocarbons : Hydrocarbons in which valencies of
atleast two carbon atoms are not fully satisfied by hydrogen atoms
and are deficient in hydrogen as compared to alkanes, are said to
be unsaturated.
(b) Olefins : Alkenes are known as olefins (latin : Oleum = oil; ficare =
to make). They have tendency to form oily products on treatment
with halogens.
(c) General formula : The general formula of alkenes is CnH2n.
Alkenes have two hydrogen atoms less than the corresponding
alkanes which have general formula CnH2n + 2.
There is no alkene corresponding to methane (CH 4), hence the
first member of the alkene series is ethene (ethylene) (C 2H4 i.e.
CH 2 = CH 2) which corresponds to the alkane-ethane (C 2H 6 i.e.
CH3-CH3).
(d) Reactivity of alkenes : Alkenes are more reactive than alkanes
due to the presence of >C = C< carbon-carbon double bond.
(e) Nomenclature-alkenes : There are two main ways of naming
alkenes (i) Common name system : The names of alkenes are derived
from the corresponding alkane by changing the suffix - ‘ane’
into ‘ylene’. Eg. ethane to ethylene.
(ii) I.U.P.A.C. system : The names of alkenes are derived from the
corresponding alkane by changing the suffix ‘ane’ into ‘ene’.
Eg. ethane to ethene.
Structural
formula - CnH2n
Common
name
I.U.P.A.C.
name
Corresponding
alkane - CnH2n + 2
CH2=CH2
C 2H 4
Ethene CH3–CH3 ethane
Ethylene
CH3CH=CH2
C 3H 6 Propylene
Propene CH3–CH2–CH 3 propane
CH 3-CH2-CH=CH2 C 4H 8 1- Butylene 1 - Butene CH 3–CH 2–CH 2–CH 3
butane
CH3-CH = CH-CH3 C 4H 8 2- Butylene 2 - Butene CH3–CH2–CH2 –CH3
butane
C 2H 6
C 3H 8
C 4 H 10
C 4 H 10
Structural formula of ethene (Ethylene) :
H
H
C === C
H
SCHOOL SECTION
H
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Introduction of alkynes :
(a) Alkynes : unsaturated hydrocarbons containing a carbon-carbon
triple bond (– C  C –) in their molecule.
(b) General formula : The general formula of alkynes is C nH2n – 2.
Alkynes have four hydrogen atoms less than the corresponding
alkanes which have general formula CnH2n + 2. The first member of
the alkyne series is ethyne (acetylene) C 2H 2. CH  CH which
corresponds to the alkane - ethane (C2H6 i.e. CH3 –– CH3).
(c) Reactivity : Alkynes are more reactive than alkenes due to the
presence of — C  C — carbon-carbon triple bond.
(d) I.U.P.A.C. system : The names of the members are derived from
the corresponding alkanes by changing the suffix - ‘ane’ to ‘yne’.
Eg. ethane to ethyne.
Structural
formula - CnH2n
Common
name
I.U.P.A.C.
name
Corresponding
alkane - CnH2n + 2
CH  CH
CH3- CH  CH
C 2H 2 Acetylene Ethyne
CH3–CH3 ethane
C 2H 6
C 3H 4 Methyl Propyne
CH3–CH2–CH 3 propane C 3H 8
acetylene
CH3- CH = CH - CH3
Dimethyl 2 - Butyne CH3–CH2–CH2 –CH3 butane C4H10
acetylene
Structural formula of acetylene (Ethyne) :
H — C  C — H
HC  CH
Q.VI
1.
Ans.
2.
Ans.
3.
Ans.
4.
Ans.
5.
Ans.
6.
Ans.
7.
Ans.
8.
Ans.
9.
Ans.
10.
Ans.
216
Answer the following questions in one sentence each :
What is organic chemistry?
The study of organic compounds is called organic chemistry.
What is catenation?
The property of direct bonding between atoms of the same element to form
chain is called catenation.
What are hydrocarbons?
Hydrocarbons are the compounds containing carbon and hydrogen elements
only.
What are saturated hydrocarbons?
Hydrocarbon in which the carbon atoms are linked to each other only by
single bond are called saturated hydrocarbon.
What are unsaturated hydrocarbons?
Hydrocarbons in which valencies of carbon are not fully satisfied by single
covalent bonds is called unsaturated hydrocarbons.
What are alkenes?
Hydrocarbons in which at least two carbon atoms are linked by double
bond (C == C) are called alkenes.
What are alkynes?
Hydrocarbons in which at least two carbon atoms are linked by triple bond
(C  C) are called alkynes.
What is vinegar?
The dilute solution (5 to 8%) of acetic acid in water is called vinegar.
What is covalent bond?
Bonds formed by sharing of electrons are known as covalent bond.
What are alkanes?
Hydrocarbons containing only single C –– C bonds are called alkanes.
SCHOOL SECTION
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11.
Ans.
12.
Ans.
13.
Ans.
14.
Ans.
SCIENCE & TECHNOLOGY
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State the number of bonds essentially present between carbon and
carbon in alkene and alkynes.
The number of bonds essentially present between carbon and carbon in
alkene and alkynes are two and three respectively.
Which organic compounds are named as alkanol in IUPAC system?
Alcohols are named as alkanol in IUPAC system.
State two examples of (organic) compounds having covalent bond and
two examples having ionic bond.
Compounds having covalent bond : Methane, sugar, L.P.G., cotton, plastic,
oil.
Compounds having ionic bond : Common salt, Copper sulphate, Ferric
chloride.
Name the first member of alkyne family.
First member of alkyne is named as ethyne or acetylene.
ACTIVITY BASED QUESTIONS
1.
Ans.
2.
Ans.
What is the IUPAC name of the following compound ?
CH3 – CH = CH – CH3
The IUPAC name CH3 – CH = CH – CH3 is But – 2 – ene (common name 2 butylene).
State the number of bonds essentially present between carbon and
carbon in alkenes and alkynes.
In alkenes, there are carbon-carbon double bonds.
In alkynes, there are carbon-carbon triple bonds.
ACTIVITY : 9.1
Q.
Classify the following compounds used by you in terms of their origin.
(plants, animals, inorganic).
Ans.
SCHOOL SECTION
Plants and animal
Inorganic
Plastic
Oil
Sugar
Ghee
Cotton
LPG
Vinegar
Common salt
Copper
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HOTS QUESTIONS & ANSWERS
1.
Ans.
2.
Ans.
3.
Ans.
4.
Ans.
218
Meena’s father was very sick. Doctor told him to go to his native place
which is a small village away from city. What must be the reason ?
Meena’s father along with his family seems to be staying in a city. City is
considered to be polluted for various reasons. One of it is vehicles running
around. They contain petroleium which has little quantity of sulphur and
nitrogen. Their combustion results in the formation of oxides of sulphur
and nitrogen which is very dangerous for health of a person. Therefore,
doctor told Meena’s father to stay away from the city and stay in a clean
environment i.e. in a village.
A manager of a soap company was reviewing statistics of sale of soap in
village and city area. He realized that the demand for laundry soap was
more in villages than in cities. What must be the reason ? Explain in
detail.
The cloths of people in villages get dirty very soon due to working in fields
and therefore, there is a lot of demand for laundry soap. Soaps are cleansing
agents which are capable of reacting with water to dislodge the unwanted
particles from cloth or skin. The molecules of soap are sodium or potassium
salts of long chain carboxylic acids. A soap molecule has a tadpole shaped
structure. At one end (long non polar end) of soap molecule is a hydrocarbon
chain i.e. insoluble in water but soluble in oil. At the other end (short
polar end) of soap molecule, there is a carboxylate ion which is hydrophilic
i.e. water soluble but insoluble in oil. When soap is mixed with water, the
solution becomes concentrated and causes foaming. The short polar end
with the carboxylate ion turns the water away from the dirt. The soap
molecule thus helps in dissolving the dirt and the cloths are washed clean.
My mother gave me X amount to buy toilet soap. When I went to a
shop, I realized that the amount was not sufficient to buy the same. In
fact the laundry soap which was on the adjacent rack was much cheaper.
What was the reason if both were just soaps ?
Same quantity of toilet soap is costiler than that of laundry soap. Laundry
soap includes cheaper quality of fats and oils than the toilet soap whereas
the toilet soaps have expensive perfumes added in them which results
into high price for this type of soap.
Identify the following :
(a) Hydrocarbon in which carbon atoms are linked to each other only
by single bond.
(b) Bonds formed by sharing of electrons.
(c) The atom or group of atoms present in the molecule which
determines characteristics property of organic compounds.
(d) It indicates the nature and the number of carbon atoms in the basic
carbon skeleton.
(e) Ethanoic acid, below 290ºK, solidifying into an ice like mass.
(a) Saturated hydrocarbons.
(b) Covalent bonds.
(c) Functional group.
(d) Root.
(e) Glacial acetic acid.
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GLOSSARY
Element
: It is a substance that cannot be broken down
further into simpler substances.
Compound
: When two or more elements combine in a fixed
proportion.
Mixture
: Combination of two or more substances that
are not chemically united and do not exist in
fixed proportions to each other.
PVC (polyvinyl chloride)
: The electric wires that carry current in our
homes have a covering of plastic called as PVC.
Electrostatic force of attraction : A strong force of attraction between particles
of opposite charges.
Tensile strength
: It is the maximum stress that a material can
withstand while being stretched or pulled.
Density
: Mass per unit volume.
Melting point
: The melting point of a solid is the temperature
at which it changes state from solid to liquid.
Boiling point
: The temperature at which the vapor pressure
of the liquid equals the environmental
pressure surrounding the liquid.
Alkali
: Soluble bases which produce OH – ions in
water.
Oxidation
: Addition of oxygen to a substance or removal
of hydrogen from a substance.
Reduction
: Addition of hydrogen to a substance or removal
of oxygen from a substance.
Oxidising agent
: The substance that gives oxygen for oxidation
OR the substance that removes hydrogen.
Reducing agent
: The substance that gives hydrogen for
reduction or the substance that removes
oxygen.
Inorganic
: Considered to be of a mineral, not biological
origin.
Electrolytic reduction
: Electrolytic reduction is the process of
reducing the oxides of metals to their pure
form as metals.
Ion
: Ion is an atom or group of atoms which is either
positively charged or negatively charged
formed due to loss or gain of electrons.
Cations
: Positively charged ions are cations.
Anions
: Negatively charged ions are called as anions.
AMAZING FACTS
 It is estimated that a plastic container can resist decomposition
for as long as 50,000 years.
 The amount of carbon in the human body is enough to fill about
9,000 ‘lead’ pencils.

SCHOOL SECTION
219
S.S.C.
Marks : 30
CHAPTER 9 : AMAZING WORLD OF CARBON COMPOUNDS
Duration : 1 hr.
SCIENCE
Q.I
1.
2.
3.
4.
Q.I
1.
2.
3.
4.
[A] Fill in the blanks :
General molecular formula of alkane is ....................... .
Hydrocarbons necessarily contain .......................
....................... .
Molecular formula of ethane is ....................... .
....................... gas is called marsh gas.
[B] Match the columns :
Column A
Benzene
Butane
Methane
Propene
2
and
2
(a)
(b)
(c)
(d)
(e )
Column B
Green house gas
C6H 6
Unsaturated hydrocarbon
C2H 6
C 4 H 10
Q.I
1.
2.
[C] State whether True or False :
Ethene is an unsaturated hydrocarbon.
General formula of alkane is CnH2n.
1
Q.I
1.
2.
[D] Write the correlated terms :
Alkane : CnH2n + 2 :: Alkynes : ................. .
Ethane : C2H6 :: Benzene : ................. .
1
Q.II
[A] Write molecular and structural formula of the following :
(Any Two)
Butane.
Benzene.
Ethanol.
4
[B] Define the following : (Any Two)
Isomerism.
Catenation.
Saturated hydrocarbon.
2
1.
2.
3.
Q.II
1.
2.
3.
... 2 ...
Q.III [A] Distinguish between :
1.
Diamond and Graphite.
2.
Toilet soap amd Laundry soap.
4
Q.III [B] Answer in short : (Any One)
1.
What are closed chain hydrocarbons? Give examples.
2.
Write short note on Catenation.
2
Q.IV
1.
2.
3.
4
[A] Give IUPAC name of following compound : (Any Two)
CH3 – CH2 – CH2 – OH.
CH3CH = CHCH3.
CH 3COOH.
Q.IV [B] Draw electron dot and cross structure of methane.
2
Q.V
1.
2.
3.
4.
5.
[A] Answer the following in one sentence each : : (Any Four)
What are hydrocarbons?
What is covalent bond?
What is vinegar?
What are alkanes?
What are saturated hydrocarbons?
4
Q.V
1.
2.
[B] Answer the following in short : (Any One)
Write short note on Homologous series.
Explain alcohol functional group with first three alcohols.
2
Best Of Luck 