Class Notes of Ch 4 : Carbon and Its
Compound
Class 10th Science
Topics:
- Introduction
- Covalent bond in carbon
- Bonding in Hydrogen
- Bonding in Oxygen
- Bonding in Nitrogen
- Versatile nature of carbon
- Saturated Carbon Compounds
- Unsaturated Carbon Compounds
- Structural isomers
- Hydrocarbon
- Bonding of carbon with other elements
- Homologous Series
- Nomenclature of Carbon Compounds
- Chemical properties of carbon compounds
- Properties of Ethanol
- Properties of Ethanoic Acid
- Soaps
- Detergents
Introduction
All the substances that surround us have carbon components within
them. All living and non-living components in the environment are carbon
based.
Human body contains 18% of carbon and act as the basic building
block of the cells present in human body. It is necessary for the cellular
respiration of the various parts of human body.
Carbon is basically an element and is of extensive importance and
significance, both in its elemental form and in its combined form for the
survival on earth. 0.02% of carbon is present in the earth’s crust in the form
of carbonates, hydrogen carbonates, coal, petroleum and other minerals whereas
0.03% of carbon is present in the atmosphere.
Covalent Bond in Carbon
o The
elements having less than 8 electrons in their outermost shell always have a
tendency to attain an octet in order to attain a noble gas configuration by
gaining or losing electron forming ionic compounds.
o In case
of carbon with atomic number 6 there are four electrons in its outermost shell
due to which it is termed as tetravalent.
o It gains or loses four electrons to attain the
nearest noble gas configuration.
o Carbon has two possibilities to attain noble gas
configuration.
(i) One of the
possibilities is to attain four electrons and form C4– anion. But it
will be difficult for the nucleus to hold four more electrons firmly.
(ii) Another possibility is
to lose four electrons forming C4+ cation. But this
will also be difficult due to the requirement of large energy to lose four
electrons from the outermost shell. As a result the atom will contain six
protons and two electrons.
o Therefore
carbon shares its valence electrons present in its outermost shell with the
electrons in the outermost shell of the combining atoms of other elements.
o Due to
this sharing of four electrons of carbon with the electrons of other combining
atoms, carbon is said to form covalent bonds. For example, carbon shares these
electrons with four atoms of hydrogen.
o The carbon-carbon bond is very strong and hence
stable.
o Compounds possessing covalent bonds have strong
bonds within the molecule, but intermolecular forces are small leading to low
melting and boiling points of these compounds.
o Due to the sharing of electrons no charged
particles are formed i.e. no ions are formed due to which covalent compounds
are poor conductors of electricity.
Bonding in Hydrogen:
The atomic number of hydrogen is 1 and has only one electron in
its K shell.
This shell needs to either acquire or lose an electron to attain
noble gas configuration of helium.
Due to this reason two
hydrogen atoms share their outermost electrons leading to the formation of a
molecule of hydrogen, H2.
The shared pair of electrons between the hydrogen atoms
constitutes a single bond between them and is also represented by a line
between the two atoms.
Bonding in Oxygen:
The atomic number of oxygen is 8 and has six electrons in its L
shell.
This shell needs to either acquire or lose electrons two electrons
to attain noble gas configuration of Neon.
So each atom of oxygen shares two electrons with other atom of
oxygen to attain the nearest noble gas configuration.
The shared pair of
electrons between the oxygen atoms constitutes a double bond between them and
is also represented by two parallel lines between the two atoms as shown in
figure and exists as O2 molecule.
Bonding in Nitrogen:
Nitrogen has the atomic number 7 and has five electrons in its
outermost shell.
This shell needs to either acquire or lose electrons three
electrons to attain noble gas configuration of Neon.
So each atom of nitrogen shares three electrons with other atom of
nitrogen to attain the nearest noble gas configuration.
The shared pair of
electrons between the nitrogen atoms constitutes a triple bond between them and
is also represented by three parallel lines between the two atoms as shown in
figure and exists as N2 molecule.
Versatile nature of carbon
The versatile nature of carbon due to the presence of covalent
bond enables it to form a large number of compounds.
(i) Carbon due to its property of catenation possesses a unique
ability to form bonds with other atoms of carbon, giving rise to large number
of molecules and compounds having long chains of carbon, branched chains of
carbon or carbon atoms arranged in rings and linked by single, double or triple
bonds.
(ii) Carbon being tetravalent is capable of bonding with four
other atoms of carbon or any other combining mono-valent element.
(iii) Carbon forms compounds with oxygen (Carbon-dioxide),
hydrogen (Methane), nitrogen (Hydrogen cyanide), sulphur, chlorine
(Chloromethane) and many other elements giving rise to compounds with specific
properties depending upon the elements present in the compound.
(iv) The compounds formed are stable due to their strong bonds as
a result of its small size which enables the nucleus to hold the shared pair of
electrons firmly.
Saturated Carbon Compounds
o Compounds
formed by the linking of carbon by single bonds in between them are called
saturated compounds.
o These
compounds have hydrogen atoms that fill all of the other bonding orbitals of
the carbon atoms.
o For
example, Alkanes are saturated compounds. It is a series of saturated
compounds.
o
Methane with a formula CH4 is one of the
simplest compounds formed by carbon.
o The
valency of hydrogen is 1 and that of carbon is 4.
o So 4
carbon atoms share their outermost electrons with four individual hydrogen
atoms by a single bond.
o This
saturated compound is extensively used as a fuel and is one of the significant
constituent of bio-gas and Compressed Natural Gas (CNG).
o The
second compound in the series of saturated compounds is ethane with a formula
of C2H6.
o In case
of ethane three valencies of each carbon atom remain unsatisfied and hence each
carbon is bonded to three hydrogen atoms by a single bond are normally not very
reactive.
o
Unsaturated Carbon Compounds
o Compounds
formed by the linking of carbon by double or triple bonds in between them are
called unsaturated compounds.
o For
example, Ethene (C2H4) is an alkene in which
one carbon atom gets bonded to another carbon atom by a double bond. The
remaining valencies of each carbon are satisfied by two hydrogen atoms.
o Ethyne (C2H2) is an alkyne in which one carbon
atom gets bonded to another carbon atom by a double or triple bond. The
remaining valency of each carbon is satisfied by one hydrogen atom.
o These
compounds are more reactive than the saturated carbon compounds.
o Structural Isomers
Compounds having same molecular formula but different molecular
structures are known as structural isomers.
o The
following structures show the structural isomers of butane.
H H H
\ 丨∕
H H H H
H C
H
丨 丨 丨 丨
丨 丨 丨
HーCーCーCーCーH
HーCーCーCーH
丨 丨 丨 丨
丨 丨 丨
H H H H
H
H H
n-Butane
Iso-Butane
o
Structural isomer of Hexane are as follows:
CH3―CH2―CH2 ―CH2― CH2―CH3
n-Hexane
CH3
丨
CH3―CH2―CH2 ― CH―CH3
Iso-Hexane
CH3
丨
CH3―CH2―C ―CH3
丨
CH3
Neo-Hexane
Hydrocarbon
o All
carbon compounds having carbon and hydrogen are known as hydrocarbons.
o The
saturated hydrocarbons having single bonds are called alkanes. For example,
Methane, Ethane etc. The general formula for alkanes can be written as CnH2n+1, where n = 2, 3, 4.
o The
unsaturated hydrocarbons having one or more double bonds are called alkenes.
For example, Ethene, Propene, Butene, etc. The general formula for alkenes can
be written as CnH2n, where n = 2, 3, 4.
o The
unsaturated hydrocarbons having one or more triple bonds are called alkynes.
For example, Ethyne, Propyne etc. The general formula for alkynes can be
written as CnH2n-1, where n = 2, 3, 4.
Bonding of Carbon with
other Elements
o In addition to hydrogen carbon also form bonds with other
elements like halogens, oxygen, nitrogen, sulphur and many more.
o One or more hydrogen bonded to carbon can be replaced by any
of the elements mentioned above in such a way that the valency of carbon
remains satisfied.
o The element that replaces the hydrogen from the compound is
termed as a heteroatom.
o The heteroatom deliberates certain specific properties to the
compound that alters its previous behaviour irrespective of the length and
nature of the carbon chain. They are termed as functional groups.
Homologous
Series
o A series of carbon compounds in which same functional group
substitutes the hydrogen atom is called a homologous series.
o These compounds have similar chemical properties due to the
addition of same kind of functional group throughout the chain.
o For example, the series of alkanes i.e. Methane, ethane,
propane, butane and so on is a homologous series.
o The series like methanol, ethanol, propanol, butanol and so
on is also a homologous series. The functional group attached to these
compounds is alcohol.
o With the increase in molecular mass in a homologous series
the physical properties like melting points, boiling points and solubility in a
particular solvent increases.
o But the chemical properties of a homologous series determined
by the functional group remain same.
Nomenclature of Carbon Compounds
o Identify the number of carbon atoms in the compound.
No. of Carbon Atoms
|
Term to be Used
|
1
|
Meth
|
2
|
Eth
|
3
|
Prop
|
4
|
But
|
5
|
Pent
|
6
|
Hex
|
7
|
Hept
|
8
|
Oct
|
9
|
Non
|
10
|
Dec
|
o If the compound contains a functional group, it is indicated
in the name of the compound with either a prefix or a suffix.
Functional Group
|
Prefix (R-) /suffix (-R)
|
Example
|
Halogen
|
-chloro or – bromo
Depending upon the functional group added.
|
Cholorethane/ Bromoethane
|
Alcohol
|
-ol
|
Ethanol
|
Aldehyde
|
-al
|
Ethanal
|
Ketone
|
-one
|
Ethanone
|
Carboxylic acid
|
-oic acid
|
Ethanoic acid
|
o The functional group present in the compound is
indicated as suffix by removing the e at the end and adding the appropriate
suffix as discussed in the table. For example, a two-carbon chain with an
Aldehyde group would be named as: - Ethane – ‘e’ = Ethan + ‘one’ = Ethanone.
o In case of unsaturated carbon chain the final ‘ane’ in the
name of the carbon chain is substituted by ‘ene’ for double bond or ‘yne’ for
triple bond.
Functional Group
|
Prefix (R-) /suffix (-R)
|
Example
|
Alkane (Single
bond)
|
-ane
|
Ethane
|
Alkene (Double
bond)
|
-ene
|
Ethene
|
Alkyne (Triple
bond)
|
-yne
|
Ethyne
|
Chemical
properties of carbon compounds
1. Combustion
o All the allotropic forms of carbon burn in the presence of
oxygen releasing carbon dioxide along with heat and light.
o The chemical equation for the carbon compounds undergoing
combustion are as follows:
(i) C + O2 → CO2 + heat and light
(ii) C2H5 (Ethane) + O2 → CO2 +
H2O + heat and light
(iii) C5H12OH (Pentanol) + O2 → CO2 +
H2O + heat and light
o Saturated hydrocarbons undergo combustion giving a clean
flame. But in the presence of limited supply of air hydrocarbons produces a
sooty flame as a result of incomplete combustion.
Gas stove at home has inlets for sufficient
supply of oxygen and hence the mixture burns giving a clean blue flame. But if
the inlets get blocked the fuel remains unburnt and hence the bottom part of
the cooking vessels gets blackened.
Combustion of fossil fuels such as coal and
petroleum containing nitrogen and sulphur leads to the formation of oxides of
nitrogen and sulphur that acts as major pollutants in the environment
Take a gas stove having clean inlets for
sufficient supply of oxygen. Burn the stove and heat a spoon. The spoon will
not get a deposition of a black layer.
Take another gas stove having blocked inlets and
heat the spoon. Soon deposition of a black layer over the spoon can be easily
observed due to insufficient supply of oxygen resulting in the production of
unburnt carbon particles.
o Unsaturated carbon compounds will give a yellow flame
releasing an enormous amount of black smoke.
2. Oxidation
Carbon compounds gets readily oxidised on
combustion. The following equation shows the conversion of alcohols to
carboxylic acid.
3. Addition Reaction
o During addition reaction an unsaturated hydrocarbon adds
hydrogen to the reaction in the presence of catalysts.
o Catalysts such as palladium or nickel proceed a reaction to a
different rate without affecting the reaction to give saturated hydrocarbons.
o This reaction is extensively used in the hydrogenation of
vegetable oils containing long unsaturated carbon chains using a nickel
catalyst.
o Animal fats on the other hand have saturated carbon chains.
4. Substitution Reaction
A reaction in which one functional group or atom
is replaced by another functional group or atom is called substitution
reaction.
In the presence of sunlight addition of chlorine
to hydrocarbons is a fast reaction that results in replacement of the hydrogen
atoms one by one. This is an example of substitution reaction because chlorine
replaces the hydrogen attached to the carbon atom in the hydrocarbon.
Properties
of Ethanol
o Ethanol exists in liquid state at room temperature.
o Mixture of alcohol to ethane results in the formation of
ethanol and it is the active ingredient of all alcoholic drinks. Even a small
quantity of ethanol if consumed can causes drunkenness.
o Being a good solvent, it is also used in medicines like
tincture of iodine, cough syrups, and many other tonics.
o Reactions of Ethanol
o Reaction with sodium –
Reaction of alcohols with sodium leads to the
evolution of hydrogen. Reaction of sodium with ethanol the product formed along
with hydrogen is sodium ethoxide.
o Reaction to give unsaturated hydrocarbon:
Reaction of ethanol with excess concentrated
sulphuric acid acting as dehydrating agent at 443 K results in the dehydration
of Ethanol leading to the formation of Ethene.
Soaps
o Dirt is oily in nature and hence does not dissolve in water.
o To removes these dirt we often use soaps that contains sodium
or potassium salts of long-chain carboxylic acids.
o In soap the ionic-end is hydrophilic and hence dissolves in
water.
o The end containing carbon chain is hydrophobic and hence
dissolves in oil leading to the formation of structures called micelles that
dissolves the dirt in water thereby making it easier to clean the clothes.
o This leads to the creation of emulsion in water.
o But in case of hard water it becomes difficult to form foam
and the forms scum with the salts of hard water. In that case another kind of
cleansing agent used is known as detergents.
Detergents
o Detergents are cleansing agents possessing ammonium or
sulphonate salts of long chain carboxylic acids that are used to clean clothes
in hard water.
o Hard water is the water containing calcium and magnesium
carbonates. Soap forms lather with these carbonate salts thereby making it
difficult to clean the clothes.
o The charged ends of detergent do not form scum or
precipitates with the calcium and magnesium ions present in hard water.
o Therefore they remain effective in cleaning dirt in hard
water as compared to soap.
o They are also used for manufacturing shampoos and various
cleansing products.
SCIENCE Revision Notes
Chapter:01 Chemical Reaction & Equation
Chapter:02 Acid Base & Salt
Chapter:03 Metals & Non Metals
Chapter:04 Carbon & its Components
Chapter:05 Periodic Classification of Elements
Chapter:06 Life Processes
Chapter:07 Control & Coordinates
Chapter:08 How do Organisms Reproduce
Chapter:09 Heridity & Evolution
Chapter:10 Light Reflection Refraction
Chapter:11 The Human Eye & the Colourful World
Chapter:12 Electricity
Chapter:13 Magnetic Effect of Electric Current
Chapter:14 Source Of Energy
Chapter:15 Our Environment
Chapter:16 Management of Natural Resource
Maths Revision Notes
English Revision Notes
Economics Revision Notes
Chapter:01 Chemical Reaction & Equation
Chapter:02 Acid Base & Salt
Chapter:03 Metals & Non Metals
Chapter:04 Carbon & its Components
Chapter:05 Periodic Classification of Elements
Chapter:06 Life Processes
Chapter:07 Control & Coordinates
Chapter:08 How do Organisms Reproduce
Chapter:09 Heridity & Evolution
Chapter:10 Light Reflection Refraction
Chapter:11 The Human Eye & the Colourful World
Chapter:12 Electricity
Chapter:13 Magnetic Effect of Electric Current
Chapter:14 Source Of Energy
Chapter:15 Our Environment
Chapter:16 Management of Natural Resource
Maths Revision Notes
English Revision Notes
Economics Revision Notes
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