Download CARBON AND ITS COMPOUNDS

CARBON AND ITS COMPOUNDS
1.Give atomic number electronic configuration group number and valency of carbon?
Atomic number = 6
Electronic configuration = 2,4
Group number = 16
Valency = 4
2.Carbon forms mainly co valent compounds. Explain
Atomic number of carbon is 6.Therefore its electronic configuration is 2,4.
Thus carbon has 4 electrons in its valence shell.
To complete octet it should either lose 4 electrons or gain 4 electrons .
It can not lose 4 electrons as it needs large amount of energy. It cannot gain 4
electrons as the ion formed would be highly unstable.
Therefore it completes its octet by sharing 4 electrons and thus forms covalent
compounds.
3.Carbon forms large number of compounds .Give two reasons .
Te two main reasons why carbon makes large number of compounds are
1.Catenation:-Self linking property of carbon through covalent bonds forming
chains of varying lengths leads to large number of compounds.
2.Tetravalency of carbon:-It can form four bonds either with carbon or other
atoms. It can also form multiple bonds. These also lead to large number of
compounds.
4.Define co valent bonds.
The bonds formed by mutual sharing of electrons between atoms to complete
octet (or duplet ) are called co valent bonds.
The number of electrons contributed by each atom is called co valency.
5.Carbon is tetra valent.and tetra hedral Explain.
Carbon has four electrons in its valence shell.(electronic conf =2,4)
Therefore it forms four co valent bonds by sharing these 4 electrons with other
atoms.Thus carbon is a tetra valent element.
These 4 bonds lie along the corners of a tetrahedron and angle between the bonds
is 1090 28’.
6.Explain the formation of following molecules.
H2, Cl2, O2, N2, H2O, NH3, CH4
H2:-Atomic number of H is 1.
Its electronic configuration is 1 and thus requires 1 electron to complete the K
shell.(duplet).So H shares one electron each to form H2 molecule.
Cl2: -Atomic number of Cl is 17.
Its electronic configuration is 2,8,7 and thus requires one electron to complete its
octet (8).
So two Chlorine atoms share one electron each to form Cl2 molecule.
O2:- Atomic number of O is 8
Its electronic configuration is 2,6 and thus requires two electrons to complete its
octet (8).
So two oxygen atoms share two electrons each to form O2 (double bond)
molecule.
N2: - Atomic number of N is 7
Its electronic configuration is 2,5 and thus requires three electron to complete its
octet (8).
So two oxygen atoms share two electrons each to form O2 (double bond)
molecule.
H2O: -Atomic number of O is 8. Its electronic configuration is 2,6 and thus
requires two electrons to complete its octet (8).
Atomic number of H is 1.
Its electronic configuration is 1 and thus requires 1 electron to complete the K
shell.(duplet)
Thus O shares two of its valence electrons with each H atom to form H2O.
NH3: - Atomic number of N is 7. Its electronic configuration is 2,5 and thus
requires three electrons to complete its octet (8).
Atomic number of H is 1.
Its electronic configuration is 1 and thus requires 1 electron to complete the K
shell. (Duplet)
Thus N shares three of its valence electrons with each H atom to form NH3.
CH4: - Atomic number of C is 6. Its electronic configuration is 2,4 and thus
requires four electron to complete its octet(8).
Atomic number of H is 1.
Its electronic configuration is 1 and thus requires 1 electron to complete the K
shell. (Duplet)
Thus C shares four of its valence electrons with each H atom to form CH4.
7.Give any four properties of covalent compounds.
1.They are formed by the mutual sharing of electrons between two atoms.
2.They generally have low melting and boiling points due to week inter molecular
force of attraction.
3.They are generally bad conductor of electricity as they do not contain any ions.
4.They are generally insoluble in polar solvents like water but are soluble in non
polar solvents or organic solvents like alcohol.
8.What is meant by allotropy? Which are the allotropic forms of carbon?
The phenomenon of existence of an element in two or more forms, which have
different physical properties but same chemical properties, is called allotropy.
The allotropes of C are
1.Diamond
2.Graphite
3.Fullerenes
9.What is meant by isomerism?
The compounds having same molecular formula but different structural formula
are called isomers. This phenomenon is called isomerism.
10.What are saturated and unsaturated carbon compounds?
The compounds of carbon, which have only single bonds between the carbon
atoms, are called saturated compounds.
Eg methane(CH4) ,ethane(CH3-CH3) , propane (CH3 -CH2 – CH3 )etc
The compounds of carbon, which contain one of more double, or triple bonds
between carbon atoms are called unsaturated compounds.
Eg ethene CH2 = CH2, ethyne CH CH etc.
11.What are hydrocarbons ? give examples
The compounds of carbon and hydrogen are called hydrocarbons.
E.g. methane (CH4 ), ethane(CH3-CH3 )
12.What are homologous series?
The series of organic compounds
1.which can be represented by a general formula,
2.adjacent members differ by CH2 group,
3.having similar methods of preparation,
4.having similar chemical properties.
Eg:- alkanes,alkenes,alkynes, alcohols etc
13.Give the general formula of the following homologous series
alkanes,alkenes,alkynes,alcohols,acids,aldehydes.
Alkanes-CnH2n + 2
Alkenes-CnH2n
Alkynes-CnH2n -2
Alcohols-CnH2n +1OH
Acids- CnH2n +1 COOH
Aldehydes- CnH2n +1 CHO
14.What are functional groups? Give examples.
An atom or a group of atoms present in a molecule which determines its
properties is called functional group.
Molecules which have same functional group show similar chemical properties
while those having different functional groups show different chemical properties.
Common Functional Groups
Functional Group Name
F, Cl, Br, or I
Example
Alkane
CH3CH2CH3 (propane)
Alkene
Alkyne
Alkyl halide
Alcohol
Ether
Amine
CH3CH=CH2 (propene)
CH3CCH (propyne)
CH3Br (methyl bromide)
CH3CH2OH (ethanol)
CH3OCH3 (dimethyl ether)
CH3NH2 (methyl amine)
Functional Groups That Contain a Carbonyl
Functional Group Name
Example
Aldehyde
CH3CHO (acetaldehyde)
Ketone
CH3COCH3 (acetone)
Acyl chloride
CH3COCl (acetyl chloride)
Carboxylic acid CH3COOH (acetic acid)
Ester
CH3COOCH3 (methyl acetate)
Amide
CH3CONH2 (acetamide)
15.What is meant by combustion? What happens if the following compounds are
combusted? a) CH4 , CH3-CH2-OH
Heating a substance strongly in the presence of excess of oxygen or air is called
combustion.
During combustion C in the compound gets oxidised to CO2 and H gets oxidised
to H2O.
CH4 + 2O2  CO2 + 2H2O + Heat and light
CH3-CH2-OH + 3O2  2CO2 + 3H2O + Heat and light.
16.Do saturated compounds burn differently from unsaturated compounds ? Give reason.
Saturated compounds burn with a blue flame in excess of air or oxygen but
unsaturated compounds burn with a yellow flame with lots of black smoke.
This is because the carbon content of the unsaturated compounds is more than the
hydrogen content and hence carbon is not completely burned.
Saturated compounds also burn with a sooty flame if the supply of air is limited.
17.What is meant by oxidation reaction?What happens when ethanol is oxidized?
Addition of oxygen to a substance or removal of hydrogen from a substance is
called oxidation.
The substances which are capable of doing this are called oxidizing agents.
Alkaline KMnO4 and acidic K2Cr2O7 are examples of oxidizing agents.
When ethanol is oxidized using alkaline KMnO4 it forms ethanoic acid.
CH3-CH2-OH + 2[O] alkKMno
4 CH3-COOH
18.What are addition reactions ? Give one example.
The reactions, which involve addition of two reactants to form a single product,
are called addition reactions.
Eg.Unsaturated alkenes add hydrogen in the presence of catalyst nickel, platinum
or palladium to form saturated hydrocarbons (alkanes).
Ni
CH2 = CH2 + H2 
CH3 - CH3
This process is called hydrogenation.
19.How are vegetable oils different from animal fats? How are oils converted to fats?
Vegetable oils generally have long unsaturated carbon chains while animal fats
have saturated carbon chains.
Vegetable are converted to fats by hydrogenation.
K
Vegetable oil + H2 Ni
, 473


 Vegetable ghee
20.What is the need for hydrogenation of oils?
When vegetable oils are exposed to hot and humid weather for a long time it turn
rancid ie they develop unpleasant smell and taste.(rancidity).
Hydrogenation slows down the process of rancidity.
21.What are substitution reactions ? Give one example.
Reactions which involve the displacement or substitution of an atom or a group of
atoms in one organic molecule by another atom or group of atoms are called
substitution reactions.
CH4 + Cl2 sunlight
 CH3Cl + HCl
With excess of chlorine all the hydrogen atoms are replaced by chlorine one by
one to form many products.
CH3Cl + Cl2 sunlight
 CH2Cl2 + HCl
CH2Cl2 + Cl2 sunlight
 CHCl3 + HCl
CHCl3 + Cl2 sunlight
 CCl4+ HCl
22.Give any 3 physical properties of ethanol. (CH3-CH2-OH)
1.Ethanol is colour less liquid at room temperature.
2.It is soluble in water.
3.It has a distinct smell and a burning taste.
23.How does ethanol react with sodium?
Ethanol reacts with sodium to form sodium ethoxide with the evolution of
hydrogen gas.
2CH3-CH2-OH + 2Na  CH3-CH2- ONa + H2
24.What is the action of CONC.H2SO4 on ethanol?
CONC.H2SO4 is a dehydrating agent. Therefore it removes a molecule of H2O
from ethanol to form ethene.
. H 2 SO4, 443K
CH3-CH2-OH CONC


 CH2=CH2 + H2O
25.Give any three uses of ethanol.
1.Ethanol is used in alcoholic beverages like beer, rum, whisky etc.
2.It is used in industry as solvent for paints, perfumes, cough syrup etc.
3.It is used in preparation of dyes, cosmetics, transparent soaps, chemicals like
chloroform, iodoform ether etc.
26.What are the harmful effects of drinking alcohol?
Consumption of alcohol
Slows down metabolic processes,
Depress central nervous system,
Results in lack of co-ordination, mental confusion,
Drowsiness,
Sense of timing and judgment,
and damage liver and kidney.
27.What is meant by denatured alcohol or methylated spirit?
To prevent the misuse of industrial alcohol for drinking purposes it is made unfit
for drinking by adding certain poisonous substances such as methyl
alcohol,pyridine etc.
This is called denaturation of alcohol and the alcohol is called denatured alcohol.
28.Define fermentation.
Fermentation may be defined as the slow decomposition of big organic molecules
in to simpler molecules in the presence of enzymes.
29.Give the common name,molecular formula ,functional group and the structure of
functional group present ethanoic acid.
Ethanoic acid Molecular formula= CH3-COOH
Common name = acetic acid.
Functional group = -COOH (Carboxylic acid group)
Structure of functional group=
30.How does ethanoic acid react Sodium?
Na reacts with ethanoic acid evolving hydrogen gas and form metal salt .
Ethanoic acid gives sodium ethanoate and hydrogen.
2CH3-COOH + 2Na  2CH3-COONa + H2
31.How does ethanoic acid react with sodium hydroxide?
Ethanoic acid reacts with sodium hydroxide to give a salt and water .
CH3-COOH + NaOH  CH3-COONa + H2O
32.How do ethanoic acid react with a)sodium carbonate(Na2CO3) and b) sodium bi
carbonate(NaHCO3)?
Ethanoic acid reacts with both Na2CO3 as well as NaHCO3 to form salt sodium
ethanoate ( sodium acetate ) ,and water with the evolution of CO2.
2CH3-COOH + Na2CO3  2CH3-COONa + H2O + CO2
CH3-COOH + NaHCO3  CH3-COONa + H2O+ CO2
This reaction is used as a test of carboxylic acids.
33.What is meant by esterification? Explain with one example.
The reaction between a carboxylic acid and an alcohol results in the formation
of an ester. This reaction is called esterification.
For example ethanoic acid when warmed with ethanol in the presence of a few
drops of conc H2SO4 an ester - ethyl ethanoate ( or ethyl acetate) is formed.
. H 2 SO4
CH3-COOH + HO-CH2-CH3 CONC

 CH3-COO –CH2-CH3 + H2O
34.What are esters.
Esters are sweet smelling substances.Perfumes &flowers contain esters.They are
formed by esterification ie the reaction between carboxylic acids and alcohols in
the presence of conc sulphuric acids.
35.Explain the term saponification.
Alkaline hydrolysis of an ester to give salt of the corresponding acid and the
alcohol is called saponification.
It is the reverse of esterification.
CH3-COO-CH2-CH3 +NaOH HEAT
 CH3-COONa + CH3-CH2-OH
36.Give chemical test to detect the presence of 1) ethanol 2)ethanoic acid 3)ester
1)Sodium metal test:-Ethanol can be detected by adding a piece of dry sodium
.Hydogen gas is evolved which burns with a pop sound.
2CH3-CH2-OH + 2Na  CH3-CH2- ONa + H2
2.)Sodium bicarbonate test:-To a little ethanoic acid taken in a test tube add
solution of sodium bicarbonate.Brisk effervescence is seen due to the formation of
CO2.
CH3-COOH + NaHCO3  CH3-COONa + H2O+ CO2
3)Saponification test:- Take a little ester and NaOH solution in a test tube.They
make two separate layers.On heating the mixture in a water bath the two layers
merge together to become a single layer.This is because the sodium ethanoate and
ethanol formed are soluble in water.
 CH3-COONa + CH3-CH2-OH
CH3-COO-CH2-CH3 +NaOH HEAT
37.What are soaps and detergents?
Soaps are sodium or potassium salts of higher fatty acids like palmitic acid or
stearic acid.
Detergents are ammonium or sulphonate salts of long chain hydrocarbons.
38.How is soft water different from hard water?
Water that produce lather with soap readily are called soft water.
Water that does not produce lather with soap readily is called hard water.Hardness
of water is due the presence of bicarbonates,chlorides,and sulphates of calcium
and magnesium.
39.What are the advantages of detergents over soap for washing purposes?
1.Detergents can be used in hard water where as soap can not be used.
2.Cleansing power of synthetic detergents is much higher than those of soaps.
3. Detergents are more soluble in water than soap.
40.Explain cleansing action of soap and detergents.
1.Both soap and detergents are made up of two parts.long hydrocarbon part and
negatively charged head.
2.Hydrocarbon part is hydrophobic(water repelling) and negatively charged head
is hydrophilic(Water attracting).
3.The dirt is generally held to the surface by a thin layer of oil of gre
4.When dirty cloth is treated with soap or detergent solution,the non polar
hydrocarbon tail attach with oil or grease and the polar heads are held by
surrounding water.
5.When agitated the loosened oily dirt particles are removed from the surface
and cloth is cleaned.
41.What do you understand by isomerism? Ilustrate with one example.
Compounds having same molecular formula but different structures are called
isomers.
Isomers have different physical and chemical properties.
Eg: C4H10 has two isomers.
CH3-CH2-CH2-CH3 (N-BUTANE) and CH3-CH-CH3(ISOBUTANE)
CH3
42.An organic compound burns with sooty flame . Is it saturated or unsaturated?
Due to high carbon and low hydrogen content , unsaturated organic compounds
burn with a sooty flame.
43.What is vinegar?
A 5-8% aqueous solution of acetic acid( ethanoic acic ) is called vinegar.
44.Give one equation of the reaction which shows the acidic nature of ethanol.
Ethanol reacts with sodium to form sodium ethoxide with the evolution of
hydrogen gas.
2CH3-CH2-OH + 2Na  CH3-CH2- ONa + H2
45.Compare the properties of soap and detergent.
1. Soaps cannot be used in
hard water
2. Soap is made from
vegetable oil or edible oils
3. Soaps cannot be used in
acidic medium ( otherwise
precipitate the fatty acids)
4. Soaps have weak
cleansing action
5. Soaps are not very
soluble in water
6. Soaps are biodegradable
and do not cause pollution
1. Synthetic detergents can
be used in hard water
2. Synthetic detergents
made from byproducts of
petroleum industry ( to
conserve
edible
oil)
3. Synthetic
detergents
can
be used in any medium
including acidic.
4. Synthetic detergents have
strong cleansing action.
5. Synthetic detergents are
highly soluble
6. Synthetic detergents are
not biodegradable and
cause water pollution