CARBON AND IT'S COMPOUND[PART 2], CLASS 10, SCIENCE

1
CLASS 10 SCIENCE
CARBON
AND
ITS COMPOUNDS
[CHAPTER : 2]

2
Q. What are alkynes?
A. Alkynes are unsaturated hydrocarbons containing at least one
carbon-carbon triple bond. The general formula of alkynes is CnH2n-2.
Q. Give the electron dot structure of ethyne.
A.
Image Source : Study Page

3
Q. Derive the structure of pentyne.
A. Pentyne is an unsaturated alkyne hydrocarbon
compound with five carbon atoms and a triple bond.
Here, ‘pent’ means five and ‘yne’ means triple bond. As
the general formula is CnH2n-2, the molecular formula of
pentyne is C5H8. It has one carbon-carbon triple bond,
three carbon-carbon single bond and eight carbon-
hydrogen bonds.

4
A. STRUCTURE OF PENTYNE:
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5
Q. Give the structure of butyne.
A.
Image Source : UCLA

6
Q. What are Closed Chain compounds?
A. Closed Chain compounds are the compounds in which the
carbon atoms are linked to each other by covalent bonds and these
compounds contain one or more closed chains(rings) of atoms.
Q. What are the different types of closed chain compounds?
A. Closed Chain compounds are classified into two types namely:
1. Homocyclic compounds
2. Heterocyclic compounds

7
Q. What are alicyclic compounds?
A. The compounds containing ring of three carbon atoms
are called alicyclic compounds.
Q. What are cycloalkanes? What is their general formula?
A. The saturated hydrocarbons containing cyclic structures,
are called cycloalkanes. Their general formula is CnH2n,
where n= 3,4,5, ..., etc.

8
Q. Give the structure of Cyclobutane.
A.
Image Source : Embibe

9
Q. Give the structure of cyclopentane.
A.
Image Source : UCLA

10
Q. Give the structure of cyclohexane.
A.
Image Source : Pediaa.Com

11
Q. What are aromatic compounds?
A. The cyclic compounds containing one or more hexagonal
rings of carbon atoms with three double bonds(=) in alternate
position are called aromatic compounds.
Q. What are heterocyclic compounds?
A. The cyclic compounds in which the ring atoms are made
up of heteroatoms like nitrogen, oxygen and sulphur in
addition to carbon atoms are called heterocyclic compounds.

12
Q. Give the structure of phenol.
A. Molecular formula of phenol : C6H5OH
Structural Formula:
Image Source : TCI AMERICA

13
Q. List the characteristics of organic compounds.
A. General characteristics of organic compounds:
1. Organic compounds contain complex structures and
have high molecular weights.
2. These are soluble in organic solvents, but mostly
insoluble in water.
3. Mostly includes only three elements: Carbon,
Hydrogen, and Nitrogen.

14
Q. Define homologous series.
A. The homologous series can be defined as a group of
organic compound having similar structures and chemical
properties in which the successive compounds differ by
methylene(-CH2) group.
Q. Explain homologous series with examples.
A. If we consider propane and butane, both are successive
members of alkanes. The molecular formula of propane is
C3H8 and that of butane is C4H10. If we compare the
molecular formula of both, we see that it differs in -CH2 group.

15
Q. List the characteristics of homologous series.
A. The characteristics of homologous series are as follows:-
1. All the members of a homologous series can be
represented by the same general formula. For example,
alkanes(CnH2n+2), alkenes(CnH2n) and alkynes(CnH2n-2).
2. Any two adjacent homologues differ by -CH2 group that is
by 1 carbon atom and 2 hydrogen atoms. For example,
methane(CH4) and ethane(C2H6) in the homologous series
differ by methylene(-CH2) group.

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3. The difference in molecular mass of any two adjacent
homologues is 14u. For example, the molecular mass of
methane(CH4) is 16u and that of next successive member
ethane(C2H6), is 30u, so the difference in molecular masses is
14u.
4. The members of a homologous series show a gradual change
in their physical properties with increase in molecular mass.
For example, increase in carbon atom down the series increases
melting point, boiling point and densities of its member.
5. All the members of homologous series show similar chemical
properties.

17
Q. What is functional group?
A. A functional group is an atom or group of atoms that define the
function of the hydrocarbon that they get attached to. These
functional groups are responsible for the chemical properties of an
organic compound.
Q. List any three functional group with their structure.
A. 1. Hydroxyl group(-OH).
2. Ketonic group(-CO-)
3. Aldehyde group(-CHO)

18
Q. Illustrate terminal and non-terminal groups with
examples.
A. The functional groups may be of two types namely:
1. Terminal functional group.
2. Non-terminal functional group.
1. Terminal functional group: In a terminal functional
group, the three valencies of carbon atom are satisfied
and are found at the end of the chain.

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Terminal functional group:
Image Source: Tutormate

20
2. Non-terminal functional group: In a non-terminal functional
group, only two valencies of carbon atom are satisfied and are
not present at the end of the chain.
Image Source: Quora

21
Q. What are alkyl groups?
A. The structural formula of a hydrocarbon has two
parts namely, Alkyl group and Functional group. These
two parts are linked to each other by covalent bond. The
removal of one hydrogen atom from the molecule of an
alkane gives an alkyl group.
The general molecular formula of alkyl group is CnH2n+1.
Usually, they are represented by the letter ‘R’.

22
Q. What are the two types of nomenclatures?
A. The two types of nomenclatures are as follows:
1. Common names or Trivial names.
2. IUPAC names or Systematic names.
Q. Expand IUPAC.
A. International Union of Pure and Applied Chemistry.

23
Q. How common names were obtained? Give an
example.
A. The common names were given after the source
from which the organic compounds were obtained.
These names have no proper system of naming.
Example: Acetic acid
It is obtained from ‘acetum’ which means ‘vinegar’.
Since, it is present in vinegar, it is named ‘acetic acid’.

24
Q. What are the four parts of a name of a compound in
the IUPAC system of nomenclature?
A. The correct sequence for naming a compound by
IUPAC is as follows:
1. Prefix
2. Root word
3. Primary suffix
4. Secondary suffix

25
Q. What is the use of primary suffix? Give examples.
A. A primary suffix indicates the degree of saturation or
unsaturation in carbon compounds.
Example: For carbon atoms linked by:
A single covalent bond, suffix: ane is used.
A double bond, suffix: ene is used.
A triple bond, suffix: yne is used.

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Q. What is the use of secondary suffix? Give examples.
A. The secondary suffix is used to indicate the main
functional group in the organic compound and is added
immediately after the primary suffix in the IUPAC name.
For example, if a compound has alkane and alcohol group
attached to it, the naming will be alkanol, -ol being the
suffix for alcohol.
For aldehyde, the secondary suffix for an aldehyde is -al.

27
Q. What is the use of ‘root word’? Give any two examples.
A. The ‘root word’ is also called ‘word root’. It denotes ‘the
total number of carbon atoms’. The ‘root word’ represents
the number of carbon atoms in the longest continuous
chain of C-atoms including the functional group and the
multiple bonds if any.
For example, ‘Meth’ refers to a chain with 1 carbon atom.
‘Pent’ refers to a chain with 5 carbon atoms.

28
Q. Explain the rules of IUPAC nomenclature.
A. Rules of IUPAC nomenclature:
1. To select the longest chain of carbon atoms known as
parent chain, to determine the parent name(root word).
2. The parent chain include double or triple bond along
with the terminal functional groups.
3. The numbering starts from one end in such a way that
the carbon atom involving multiple bonds gets the least
possible number.

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4. If a terminal functional group is present, the
numbering of the chain must start from the carbon atom
of the functional group.
5. The positions of suffix or prefix are indicated by the
numerical figures before their names, and are separated
by hyphen(-).

30
Q. What are the different classes of organic compound and general
formula?
A.1. Alkanes (CnH2n+2)
2. Alkenes (CnH2n)
3. Alkynes (CnH2n-2)
4. Halokanes (CnH2n+1X)
5. Alcohols (CnH2n+1OH)
6. Aldehydes (CnH2n+1CHO)
7. Ketones (CnH2n+1CO)
8. Carboxylic acid (CnH2n+1COOH)

31
Q. Define isomerism.
A. Isomerism is the existence of two or more different organic
compounds with the same molecular formula but different structures.
Q. What are the possible isomers of organic compound having
C4H10?
A. C4H10 or Butane exists in two isomeric forms:
1. CH3-CH2-CH2-CH3 (n-butane)
2.

32
Q. What happens when a fuel is burnt? Give equations.
A. When carbon containing fuels, such as coal, charcoal
are burnt, it produces carbon dioxide with large amont of
heat and light.
C+O2 ---> CO2 + HEAT +LIGHT
Q. What are fossil fuels?
A. The natural resources which are formed from the
dead remains of living organisms(fossils) are known as
fossil fuels. Coal, natural gas and petroleum are
examples of fossil fuels.

33
Q. How coal is formed?
A. The decomposition of large land plants and trees that
got buried under the earth millions of years ago resulted
in the formation of coal. It was believed that due to
earthquakes and volcanoes, the forest were buried
under the earth’s surface and were covered with sand,
clay and water. Due to high pressure and temperature
inside the earth and in absence of air, the wood was
converted into coal.

34
Q. What is crude oil?
A. The unrefined oil pumped out the ground is called
crude oil. It is a type of fossil fuel. Crude oil is refined to
obtain various usable products such as petrol, kerosene
etc. Crude oil varies greatly in appearance depending on
its composition.
Q. Name some fuels obtained from petroleum.
A. The fuels like Liquefied Petroleum Gas(LPG), diesel,
kerosene and petrol are obtained from petroleum.

35
Q. How are petroleum and natural gas formed?
A. It was believed that microscopic plants and animal which lived
in seas died and their body sank to the bottom of the sea. These
were soon covered with mud and sand in the presence of high
pressure and heat. The bacteria converted the remains of these
microscopic plants and animals into petroleum oil and natural gas
in the absence of oxygen. The petroleum oil formed got trapped
in between the layers of non-porous rocks and natural gas
formwd was above it.. Thus, petroleum oil and natural gas were
formed by the decomposition of remains of microscopic plants
and animals buried under the sea millions of years ago.

36
Q. Why is petroleum called rock oil?
A. Petroleum called rock oil because petroleum is found to
be trapped between rocks under the earth’s crust.
Q. Define flame. When it is produced?
A. A flame is a region where burning (combustion) of
gaseous substance takes place.
A flame is produced only when gaseous substances are
burnt. All the gaseous fuels burns with a flame, but only
those solid and liquid fuels which vapourize on heating
produces a flame.

37
Q. What are two types of flames?
A. When a fuel is burnt, it produces two types of flames:
1. A blue flame.
2. A yellow flame.
Q. How are the fuels burnt in sufficient supply of oxygen?
A. When the oxygen supply is sufficient, then the fuels
burn completely to produce a non-luminous (or non-light)
giving) blue flame.

38
Q. How are the fuels burnt in insufficient supply of oxygen?
A. When the oxygen supply is insufficient, then the fuels burn
incompletely to produce a luminous (or light giving) yellow flame.
The yellow colour of flame is due to the glow of hot, unburnt
carbon particles produced by incomplete combustion of the fuel.
Q. Explain the flame formed in cooking gas in gas stove.
A. In a gas stove, the cooking gas burns with non-luminous flame.
This is because the gas stove has holes for air to mix properly
with cooking gas. The cooking gas thus gets sufficient oxygen
from air and so it burns completely producing a blue flame.

39
Q. Explain the flame when a candle is burnt?
A. When the candle is lighted, the wax melts, rises up
the wick and gets converted into vapours. Thus, thecles
wax in the candle burns in insufficient supply of oxygen
resulting in incomplete combustion of wax. This
produces small unburnt carbon particles, which rise in
flame and give out yellowish light. These unburnt carbon
particles, leave the candle flame as soot and smoke.

40
Q. What happens when solid or liquid fuels are burnt?
A. When burnt, the solid or liquid fuels which do not
vaporize on heating, do not produce a flame. For
example, coal and charcoal in ‘Agarbathi’ just glows red
and gives heat without producing any flame. When coal
or charcoal is burnt, the volatile substances in it vaporize
and burn with a flame in the beginning. But after all the
volatile substances are burnt, the remaining coal or
charcoal glows red and gives heat without producing any
flame.

41
Q. Name a few chemical properties of carbon
compound.
A. Carbon mainly takes part in four types of chemical
reactions which are as follows:
1. Oxidation reactions
2. Addition reactions
3. Substitution reactions
4. Combustion reactions

42
Q. Name the reactions that saturated and unsaturated
hydrocarbons undergo?
A. The saturated hydrocarbons undergo substitution
reactions whereas unsaturated hydrocarbons undergo
addition reactions.
Q. Define combustion.
A. The process of burning of a carbon compound in air to
give carbon-dioxide, water, heat and light is known as
combustion.

43
Q. What happens when methane burns in a sufficient
supply of air? Give equations.
A. When methane burns in sufficient air, then carbon
dioxide and water vapour are formed along with a
release of a lot of heat.
CH4 + 2O2 ---> CO2 + 2H2O + Heat + Light
Q. Name the major constituent of natural gas.
A. The major constituent of natural gas is methane,CH4.

44
Q. Why do saturated hydrocarbons burn with a blue
non-sooty flame?
A. The saturated hydrocarbons generally burn in air with
a blue non-sooty flame. This is because, saturated
hydrocarbons contain less carbon content, and hence
the atmospheric oxygen is sufficient to burn them. As a
result, it produces blue flame.
Q. What is the main constituent of cooking gas?
A. Butane is the main constituent of cooking gas or
LPG(Liquefied Petroleum Gas).

45
Q. Explain the combustion of alkene in sufficient supply
of air or and insufficient supply of air.
A. Complete combustion of alkenes takes place in
sufficient supply of air where there is a plentiful supply of
oxygen, and produces carbon dioxide, water.
Incomplete combustion of alkenes takes place in
insufficient supply of air where oxygen is limited and
produces water, carbon monoxide and carbon(soot). This
causes a smoky flame.

46
Q. Give reasons: “A mixture of actylene(ethyne) and air is
not used for welding.”
A. If acetylene is burnt in oxygen, it gives a clean flame with
high temperature(30000
C) due to complete combustion of
acetylene. Hence, this oxy-acetylene flame is used for welding.
When acetylene is burnt in air, incomplete burning takes place
and produces sooty flame due to limited supply of oxygen
present in the air. Therefore, it is not possible to attain such a
high temperature with air. Due to this reason, a mixture of
acetylene and air is not used for welding.

47
Q. Give the disadvantages of incomplete combustion.
A. The disadvantages of incomplete combustion are as
follows:
1. Formation of soot which is nothing but unburnt carbon
which pollutes the atmosphere.
2. Formation of carbon monoxide which is a poisonous gas.
Q. Define addition reaction.
A. Addition reaction is the reaction in which an unsaturated
hydrocarbon combines with another substance to give a
single product.

48
Q. What are catalysts?
A. Catalysts are substances which increase the speed of a
reaction without being used up.
Q. Define catalytic hydrogenation.
A. Unsaturated hydrocarbons are more reactive. So, when
hydrogen is added in presence of catalyst such as
palladium(Pd), nickel(Ni) or platinum(Pt), it forms saturated
hydrocarbons. This process of addition of hydrogen taking
place in presence of a catalyst is called catalytic
hydrogenation.

49
Q. Explain the process of hydrogenation with an
example.
A. When ethene undergoes addition reaction with
hydrogen in the presence of nickel(Ni) at 473K, it
produces ethane.
CH2=CH2 + H2 ----Ni/473K
---> CH3 – CH3
Q. Differentiate between vegetable oils and animal fats.
A.1.Vegetable oils generally have long unsaturated
carbon chains while animal fats have saturated carbon
chain.

50
2. At room temperature, vegetable oils are liquid whereas animal fats
are solid.
3. Vegetable oils are mostly derived from plants, whereas animal fats
are mostly derived from animals.
4. Vegetable oils improve cholesterol level, animal fats increase level.
Q. What are oxidizing agent? Give any two examples.
A. The substances which are capable of adding oygen to other
substances are called oxidizing agent. As for example, alkaline
potassium permanganate(KMnO4) and acidic potassium
dichromate(K2Cr2O7) are good oxidizing agent.

51
Q. How will you detect the presence of unsaturated
compounds and saturated compounds using bromine in
carbon tetrachloride?
A. Bromine in carbon tetrachloride is a test to
differentiate between the unsaturated compounds (like
alkenes and alkynes) and saturated compounds (like
alkanes). Unsaturated compounds decolourise the red
coloured bromine solution, whereas saturated
compounds do not decolourise the red colour of bromine
solution.

52
Q. Define substitution reaction.
A. The reaction in which one or more atom present in an organic compound
get replaced or substituted by suitable group or atom is called substitution
reaction. Only alkanes i.e., saturated hydrocarbons are involved in
substitution reactions.
Q. How wiil you convert alcohol to carboxylic acid?
A. Ethyl alcohol can be converted to acetic acid by yhe oxidation reaction.
Generally, this oxidation reaction takes place in the presence of alkaline
potassium permanganate (KMnO4) or acidic potassium dichromate
(K2Cr2O7).
C2H5OH+2[O] ---KMnO4/KOH
---> CH3COOH+H2O

53
Q. Explain the substitution reaction of methane.
A. When a mixture of methane and chlorine is exposed
to ultraviolet light – typically sunlight – a substitution
reaction occurs and the organic product is
chloromethane.
The reaction can be written as:
CH4 + Cl2 ----> CH3Cl + HCl

54
Q. Name and explain the reaction which is commonly used in
the conversion of vegetable oils to fats.
A. Addition reaction is used in the conversion of vegetable oil
to fats. This is called hydrogenation of oil. Hydrogenation is a
chemical process, when molecular hydrogen reacts with
another unsaturated substance in the presence of nickel (Ni)
as a catalyst. Vegetable oil generally have long chains of
unsaturated carbons, while animal fats have long chains of
saturated carbons. During hydrogenation, the double bond of
vegetable oils are broken down resulting in a saturated fat
i.e. ghee.

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CARBON AND IT'S COMPOUND[PART 2], CLASS 10, SCIENCE