Answer: it is unsaturated
compound. Unsaturated compound have low percentage of hydrogen o incomplete
combustion takes palace and produce sooty flame
.
Q.
Write next two members of the homologous series given below
C2H6,
C3H8
Answer: Since two adjacent
member of the homologous series differ by CH2, the next two members
of the homologous series will be C4H10, C4H12
Q.
What is the difference between two consecutive members in a homologous series
in alkanes in terms of (i) molecular mass (ii) number of atoms of elements.
Answer:(i) two adjacent
member of the homologous series differ by 14 a.m.u (ii) two adjacent member of
the homologous series differ by one carbon atom and two hydrogen atom[CH2]
Q.
Molecular formula of a hydrocarbon is C3 H8. Draw its complete structure and
write its name.
Answer : It is Propane
H
H H
I
I I
H – C – C - C- H
I
I I
H
H H
Q.
(a) Write chemical names of CH3COCH3, C2H5COOH.
(b) What happens when acetic acid and ethanol react in presence of concentrated
H2SO4 ? Write the reaction there in.
Anss: chemical names of CH3COCH3,
C2H5COOH are Propanone and Propenoic
acid
when acetic acid and ethanol react in presence
of concentrated H2SO4 form sweat smelling compound Easter
(Ethyl Ethanoate) .Here concentrated H2SO4 act as a
catalyst. This reaction is called Esterification.
CH3 COOH +CH3
CH2OH ⎯⎯Acid⎯→ CH3COOCH2CH3
Q.
Name an element, other then carbon, which exhibits the property of catenation
upto seven or eight atoms? Are these compounds stable?
Answer: Silicon forms
compounds with hydrogen which have chains of upto seven or eight atoms, but
these compounds are very reactive. The Silicon - Silicon bond is not very
strong and hence it is unstable.
Q.
Two elements X and Y have atomic numbers 12 and 16 respectively. To which
period of the modern periodic table do these two elements belong ? What type of
bond will be formed between them and why ?
Answer: Atomic number
of X i.e., Z = 12
Electronic configuration of
X = 2, 8, 2
Atomic number of Y i.e., Z =
16
Electronic configuration of
Y = 2, 8, 6 1
They belong to the third period.
They will form ionic bond because
X is a metal and Y is a non – metal. X loses 2 electrons which will be gained
by Y.
Q.
(a) Give a chemical test to distinguish between saturated and unsaturated
hydrocarbons.
(b) Name the products formed when ethanol burns in air. List two
forms of energy that are librated on burning ethanol.
(c) Why is the reaction
between methane and chlorine considered a substitution reaction?
Answer: (a) Bromine water
Test.:
Bromine water is yellow-red-brown in color. If unsaturated hydrocarbons are added to it
then the solution turns colorless. I.e.
the unsaturated hydrocarbons decolorize bromine water. Whereas no change takes
place to the solution when saturated hydrocarbons are added to bromine water.
Therefore this test is used
to distinguish between saturated and unsaturated hydrocarbons chemically.
(b) When ethanol burns in
air (in oxygen) gives carbon dioxide and
release heat and light.
(c) The reaction between
methane and chlorine is considered a substitution reaction because hydrogen
attached to carbon is replaced by chlorine. This reaction takes place in
presence of light and CCl4 is formed.
CH4 + Cl2 → CH3Cl + HCl (in
the presence of sunlight)
Q.
An organic compound ‘A’ of molecular formula C2H6O on
oxidation with dilute alkaline KMnO4 solution gives an acid ‘B’ with the same
number of carbon atoms. Compound ‘A’ is often used for sterilization of skin by
doctors.
(i)
Name the compounds ‘A” and ‘B’.
(ii)
Write the chemical equation involved in the formation of ‘B’ from ‘A’
Answer: (i) the compounds
‘A” and ‘B’ are alcohols
and carboxylic acids
(ii) The chemical equation
involved in the formation of ‘B’ from ‘A’
CH3 –
CH2OH
CH3COOH
Q.
(a) Explain with the help of chemical equation the following properties of
carbon compounds.
(i)
Addition Reaction
(ii) Substitution
Reaction
(b)
Differentiate between vegetable oils and animal fats.
(c) What is meant by hydrogenation ?
Answer:(a) (i) The reaction in which unsaturated hydrocarbons add
hydrogen in the presence of catalysts such as palladium or nickel to give
saturated hydrocarbons is called addition reaction.
(ii) A kind of reaction in which a chemical reagent
(substituent) displaces the another atom or group (leaving group) in a
compound, e.g., Substitution of Hydrogen of Methane by chlorine in which hydrogen of saturated hydrocarbon is replaced
by Cl one by one in the presence of sunlight is called Substitution
Reaction .
CH4 + Cl2 → CH3Cl +
HCl (in the presence of sunlight)
(b) Oils :
1.
Oils are liquid at room temperature
2. Oils containing unsaturated
fatty acids.
Fats :
1. Fats are solid at room temperature.
2. Fats containing saturated fatty acids.
(c) Hydrogenation of
vegetable oils means that molecular hydrogen in reacted with unsaturated
vegetable oils to provide vegetable oils which are partially or fully
saturated. It means to reduce or remove double bonds present in the oil. This
process is carried out in the presence of a catalyst. Hydrogenation of
vegetable oils produces vegetable oils which have higher melting point.
Example:
R2 C=CR2 + H → R2 CH-CHR2
R=
hydrogen atom or an alkyl group ;
Catalysts used are generally platinum, palladium, nickel
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