Download dandeli – 581325

LECTURER IN CHEMISTRY
BANGURNAGAR COMPOSITE
P.U.COLLEGE
DANDELI – 581325
[ NORTH CANARA ]
Empirical formula & Molecular formula
Hydrocarbon – I
1. Empirical formula :
Simplest formula which shows ratio of atoms of
different elements present in the molecule
2. Molecular formula :
Shows actual number of atoms of different
elements present in the molecule
3. Simple problems based on empirical formula &
molecular formula
Hydrocarbon – I
1. Saturated hydrocarbon - contains C-C single bond
2. Unsaturated hydrocarbon - contains C-C – double
bond or C-C triple bond
3. Alkane - Cn H2n +
2
- Paraffins (little affinity)
4. Kolbe’s reaction :
Alkanes are prepared by the electrolysis of aqueous
solution of sodium or potassium salt of carboxylic acid
Hydrogen is liberated at cathode Alkane is obtained at
anode
Methane can not be prepared by this method
5. Alkene Cn H2n - Olefin (Oil forming)
Alkene are prepared by the dehydrohalogenation of
alkylhalide
Dehydrohalogenation reaction is carried out by using
alcoholic KOH
6. Alkynes - Cn H2n - 2
Alkynes are prepared by Dehydrohalogenation reaction
7. Homolytic fission - free radicals are formed
Hetrolytic fission – electrophiles, Nucleophiles or
carbonium ion, carbanion are formed
8.
9.
Chlorination of methane
i)
Chain initiation step - free radicals are formed
ii)
Chain propagation step – free radicals formed
reacts with other molecules to form more free
radicals
iii)
Chain terminations step - All free radicals
combine to form molecules
Markownikoff`s rule :
Negative Part of reagent (unsymmetrical reagent) is
added to carbon – carbon double bond of alkene
(unsymmetrical molecule) which contains less
hydrogen atom
10.
Aromatic hydrocarbon – I
Benzene is discovered by faraday
Structure of Benzene is given by Kekule
Isolation of Benzene toluene from light oil fraction of
coal tar (00 C - 1700c ) Benzene, Toluene, xylene
90% Benzol fraction contains 70% Benzene and
25% Toluene and Thiophene
11.
Benzene reacts with chlorine in the presence of
bright sunlight to form Benzene hexachloride
(Insectside)
12.
Toluene reacts with mixture of con – HNO3 + con –
H2SO4 to from TNT ( Tri nitro toluene ) an
explosive
Toluene is used in the manufacture of saccharine –
sweeting agent
Empirical formula & Molecular formula
Hydrocarbon – I
1. Which of the following Alkane contains
Primary, Secondary, Tertiary and Quaternary
carbon atoms.
(a) (CH3)3 - CH
(b) (C2H5)3CH
(c) (CH3)3 - C - CH2 – CH - (CH3)2 (d) (CH3)4 –C
Answer :
(c) (CH3)3 - C - CH2 – CH - (CH3)2
Note :
2 When an aqueous solution containing Sodium
Acetate and Sodium Propionate is Electrolysed
we get
(a) Ethane (b) Propane (c) Butane
(d) Ethane,Propane, Butane
Answer : (d) Ethane,Propane, Butane
Note : Kolbe`s electrolysis
CH3- COONa
CH3- CH2 COONa
C2 H6 ( Ethane)
C4H10 ( Butane)
CH3- COONa + CH3- CH2 COONa
C3H8 ( Propane)
3. A gas decoloures Alkaline KMnO4 ( Baeyer`s
Regent) but does not give any precipitate with
Ammonical AgNO3 the gas is
a) Methane
(b) Ethane
Answer :
(c) Ethene
(c) Ethene
(d) Ethyne
Note :
1. Unsaturation in organic – compound is tested by using
following reagent
• Alkaline KMnO4 ( Colour of KMnO4 is decolourised )
• Bromine water ( Colour of Bromine water is
decolourised)
• Ozone ( formation of Ozonide)
2. Ammonical AgNO3 (Tollen`s reagent ) and Ammonical
Cu2 Cl2 are used to test acidic hydrogen atom in alkynes
3. Acidic Hydrogen atom is present at the end of the triple
bonded carbon atom. It is due to the higher electro
negativity of the SP – Hybridized Carbon Atom
4.
Methane is formed from the Hydrolysis of
(a)
Calcium Carbide (b)
(c)
Methanal
Answer :
(d)
(b)
Aluminum Carbide
Ethanol
Aluminum Carbide
Note :
1. CaC2 + 2H2 O
Ca (OH)2 + C2 H2
2. Al4 C3 + 12H2 O
4 Al (OH)3 + 3CH4
3. H- CHO + H2 O
No reaction
4. C2 H5 OH + H2 O
No reaction
5. A Metallic Carbide on treatment with water
gives a colourless gas which burns readily in air
and gives a red precipitate with Cu2 Cl2 + NH4 OH
the gas is
(a) Methane
Answer :
(b) Ethane (c) Ethene (d) Ethyne
(d) Ethyne ( Acetylene)
Note :
MC2 + 2H2O
C2H2 + Cu2 Cl2
M(OH)2 + C2H2
C2Cu2 + 2HCl
Red ppt
6.
Ethylene (Ethene) is used in making
(a) Antifreeze
(b) Solvent
(d) Antifreeze, Solvent, Fumigant
(c) Fumigant
Answer : (d) Antifreeze, Solvent, Fumigant
Note :
•
•
•
•
•
Antifreeze (Ethylene Glycol) A substance added to water in
radiators of motorcar engines in order to lower the freezing
point of water
Solvent ( ethylene chloride )
Fumigant (ethylene oxide ) Distraction of bacteria, Insects by
exposure to toxic – chemicals
Mustard Gas ( war gas )
Artificial Ripening of fruits
7. Addition of HI on double bond of Propene
yields Isopropyle Iodide and not n – Propyl Iodide
as the major product, because addition proceeds
through
(a) A More stable Carbonium Ion
(b) A More stable Carbanion
(c) A More stable Free Radical (d) Nucleophile
Answer :
(a) A More stable Carbonium Ion
Note : CH3–CH = CH2 + H+
1) CH3 – +CH – CH3
Iso propyl carbonium ion(More stable)
2) CH3 –CH2 – +CH2
n-propyl carbonium ion(Less stable)
8.
Markownikoff`s rule provide guidance of
addition of HBr on ?
(a) CH2 = CH2
(c) CH3 - CH = CH - CH3
(b) CH3 – CH = CH2 (d) (CH3 )2- C = C - (CH3 )2
Answer :
(b) CH3 – CH = CH2
Note :
Unsymmetrical molecule HBr adds to
Unsymmetrical Alkene
9. Two jars A and B
are filled with
Hydrocarbons Br2 in CCl4 is added to these jars
A does not decolourise the Br2 solution but B
decolourises what are A and B
(a) Alkane and Alkene (b) Alkene and Alkane
(c) Alkene and Alkyne
Answer :
(d) Alkene & Benzene
(a) Alkane and Alkene
Note : 1. Alkane are saturated compounds do not
decolourise Br2 / CCl4
2.Alkene are unsaturated compounds decolourise Br2/CCl4
(a) Acetone and Acetic Acid
(b) Acetaldehyde and Acetic Acid
(c) Acetaldehyde and Ethanol
(d) Acetone and Acealdehyde
Answer : (b) Acetaldehyde and Acetic Acid
11. A group of closely related compounds which
can be expressed by a general formula and in
which consecutive members differ by – CH2 group
is called
(a)
An Electromotive series
(b)
A Homogeneous series
(c)
A Homologous series
(d)
A Heterogeneous series
Answer : (c) A Homologous series
(a) Benzene, Ethylhalide (b) Ethylhalide, Benzene
(c) Acetaldehyde, Ethylhalide
(d) Acetic Acid, Ethylhalide
Answer :
(a) Benzene, Ethylhalide
13. Benzene reacts with Chlorine to form
benzene Hexachloride in the presence of
(a) Nickel
(b) Alcl3
(c) Bright Sunlight
(d) Zn
Answer : (c) Bright Sunlight
Note :
C6 H6 + 3Cl2
Bright sunlight C H Cl BHC Insecticide
6
6 6
14.Acetylene is used as an Anesthetic under the
name of
(a) Narcylene
(b) Pyrene
(c) Neopyrene
(d) Puridine
Answer :
(a) Narcylene
15. Which of the following is the main
component of heavy oil fraction of coal – tar
(a) Cresol and Naphthol (b) Phenol
(c) Toluene
(d) β - Naphthylamine
Answer : (a) Cresol and Naphthol
Note : 1. Light oil fraction
00 - 1700 C
2. Middle oil fraction
1700 C - 2300 C
Benzene, Toluene, Xylene
Phenol, Naphthalene
3. Heavy oil fraction
2300 C - 2700 C
Cresols, Naphthols
4. Green oil fraction
2700 C - 3400C
Anthracene, Phenanthrene
16. Benzene is less reactive than Ethene and
Ethyne towards addition reaction . This is due to
(a) Cyclic Nature
(b) Delocalisation of π – Electrons
(c) SP2 Hybridization
(d) Presence of 3 – Double Bonds
Answer : (b) Delocalisation of π – Electrons
Note : Stability of Benzene is due to Delocalisation of
π - Electrons (resonance)
17. A compound with Empirical formula CH2 O
has a vapor density of 30. It’s molecular formula is
(a) C6H12O6 (b) C2H4O2 (c) C6H12O6 (d) C3H6O3
Answer : (b)
C2 H4 O2
18. An organic compound containing C, H and N
give the following on analysis.
C = 40%, H=13.33% and N = 46.67%
What would be it’s Empirical Formula.?
(a) C2 H7 N
(b) C2 H7 N2
(c) CH3 N
(d) CH4 N
Answer : (d) CH4 N
Note :
C
H
N
40
12
13.33
1
46.67
14
= 3.33
1
= 13.33
= 3.33
4
∴ Empirical formula CH4 N
1
19. Empirical Formula of a compound is CH2O, if
it’s molecular mass is 180, then the molecular
formula will be
(a) C H O (b) C5 H10 O5 (c) C3H6O3 (d) C4H8O4
6
12
6
Answer : (a) C6H12O6
20. An Organic compound on analysis give
C = 54.5% O = 36.4% and H = 9.1% by mass
It’s Empirical formula is
(a) CH2 O
(b) CH O2 (c) C2 H4 O (d) C3 H4 O
Answer : (c) C2 H4 O
Note :
C
H
O
54.5
9.1
36.4
12
1
16
= 4.54
2
= 9.1
= 2.27
4
1
∴ Empirical formula = C2 H4 O
21. Carbon in
Benzene undergoes SP2
Hybridization and the bond angle is 120o. The
shape of Benzene Molecule is
(a) Linear
(b) Planar Hexagonal
(c) Pyramidal
(d) Tetrahedral
Answer :
(b) Planar Hexagonal
22. Which of the following can be easily
Sulphonated.?
(a) Benzene
(b) Toluene
(c) Nitrobenzene
(d) Chlorobenzene
Answer :
(b) Toluene
Note :
The electron releasing CH3 group in Toluene increases the
electron density on benzene ring and hence facilitates the
attack of Electrophile
23. According
to
Huckel,
Monoclyclic
compounds will show Aromaticity when.
(a) It has 4 π Electrons
(b) It has no π electron
(c) It has 4π
π + 2 Electrons
(d) It has (4n + 2 ) π Electrons
Answer : (d) It has (4n + 2 ) π Electrons
Note : Huckel rule : “ The no. of π electrons in an aromatic ring
is equal to (4n + 2 ) where ‘n’ is the number of benzene ring in
the compound”.
24. Aromaticity of benzene is due to
(a)
Ring
(b)
Three double bonds
(c)
Delocalisation of π Electrons
(d)
Answer :
Planar Molecule
(c) Delocalisation of π Electrons
25. Which of the following is used for artificial
Ripening of fruits
(a) Ethene
(b) Ethane
(c) Methane
(d) Ethyne.
Answer :
(a) Ethene
26.During the Chlorination of Methane to Methyl
Chloride the propagation step is represented by
Answer :
Note : 1. Reaction ‘a’ Chain initiation step
2. Reaction ‘c’ Chain propagation step
3. Reaction ‘b’ & ‘d’ Chain termination step
27. Toluene can be separated from Benzene by
(a) Washing with Con H2SO4
(b) Cooling in freezing mixture
(c) Dissolving in Sodium Hydroxide
(d) Steam distillation
Answer :
(b) Cooling in freezing mixture
28. The Hydrocarbon which is liquid at Room
Temperature
(a) Pentane
(b) Butane
(c) Propane
Answer :
(d) Ethane
(a) Pentane
Note :
Lower member of Alkanes are gases. Pantane & Hexane are
liquids. Higher members of Alkane are solids.
29.The molecular formula of a compound of a
homologous series is C3H8O.
The formula preceding it in the series is
(a) C2 H6 O
(b) C6 H10 O
(c) CH4 O
Answer :
(d) C2 H5 O
(a) C2 H6 O
Note :
Every member of a Homologous series differs by CH2 group.
Hence the preceding member should be
C3 H8 O - CH2 = C2 H6 O
30. The number of sigma and Pi bonds in a
molecule of benzene is
(a) 6 Sigma and 9 Pi
(b) 9 Sigma and 3 Pi
(c) 12 Sigma and 3 Pi
(d) 6 Sigma and 6 Pi
Answer :
(c) 12 Sigma and 3 Pi
31.Methane when heated in the absence of Oxygen
splits up to form Carbon & Hydrogen.
The process is called
(a) Pyrolysis
(c) Cracking
(b) Polymerisation
(d) Decomposition
Answer :
(a) Pyrolysis
Note :
1. Pyrolysis
: Heating the substance at high temperature
in the absence of Air or Oxygen
2. Polymerisation : Conversion of monomer to polymer
3. Cracking
: Large molecule of heavy oil cracked into small
one suitable for Petrol Engine
4. Decomposition : Breaking up of chemical compounds into
smaller molecules
32. A salt producing Hydrocarbon among these
compounds is
(a) Methane
(b) Ethane
(c) Ethyne
(d) Ethane
Answer : (c) Ethyne
Note : Ethyne forms Acetylides
33.Which of the products can not be obtained
when Chlorine is passed into boiling Toluene
(a) Benzyl Chlorine
(b) Benzal Chloride
(c) Benzotrichloride
(d) O – Chlorotolune
Answer : (d) O – Chlorotolune
34.In Benzene all the six C- C bonds have the same
bond length because of
(a) Resonance
(b) Hybridisation
(c) Isomerism
(d) Chain Isomerism
Answer :
(a) Resonance
35. Molecule in which the distance between the
two adjacent Carbon Atom is largest in
(a) Ethane (b) Ethene (c) Ethyne (d) Benzene
Answer :
(a) Ethane
Note :
1. Always single bond is larger than double or triple bond
2. In Benzene, due to delocalisation of π Electrons bond
length is between single bond & double bond.
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