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Q 1.
Name the functional group present in propanone, CH3COCH3.
Solution
Ketonic
group is present in the propanone.
Q 2.
(i) Why coal or charcoal burns with just a glow red and gives out heat without
flame while LPG burns with flame?(ii) When we light a Bunsen burner it burns
with blue flame, but sometimes we get yellow sooty flame. Why?
Solution
(i)
A coal or charcoal burns with just a glow red and gives out heat without flame
however LPG burns with flame, this is because a flame is produced only when
gaseous substances burn. When wood or charcoal is ignited, the volatile substance
present in it vapourizes and burns with a flame in the beginning. A luminous
flame is seen when the atoms of the gaseous substance are heated and start to
glow. (ii) When the air holes of Bunsen burner are open, sufficient amount of
oxygen rich air is available and it burns with blue flame. Sometimes when these
holes get blocked, due to the lack of oxygen rich air we get yellow sooty
flame.
Q 3.
Why are covalent compounds generally poor conductors of electricity?
Solution
Covalent
compounds are generally poor conductors of electricity because they do not
produce ions in solution or on melting.
Q 4.
Give a chemical test to distinguish between saturated and unsaturated
hydrocarbons.
Solution
On
adding few drops of bromine water, if brown colour of bromine disappears
quickly then the compound is an unsaturated hydrocarbon.
Q 5.
How is scum formed?
Solution
When
soap reacts with hard water, the minerals present in water react with soap and
form a white curdy substance known as scum. It reduces the cleaning ability of
soap.
Q 6.
What are aromatic hydrocarbons?
Solution
Hydrocarbons
which contain benzene and its derivative compounds are called aromatic
hydrocarbons.
Q 7.
Both carbon and silicon belong to group 14 of the periodic table. But the
tendency to exhibit catenation in carbon is much more than in silicon. Explain.
Solution
The
size of carbon atom is small as compared to that of silicon. Therefore, C-C
bond is smaller and stronger than Si-Si bond. As a result, any number of carbon
atoms can be linked to each other resulting in a large number of carbon
compounds.
Q 8.
Why is alcohol mixed with copper sulphate for industrial purposes?
Solution
Alcohol
mixed with copper sulphate for industrial purposes to make it unfit for
drinking purposes.
Q 9.
Give the names for the suffixes of the following functional groups: -COOH;
-CHO; -OH; -CO-
Solution
The
suffix names for the functional groups are:1. -COOH is -oic acid2. -CHO is
-al3. -OH is -ol4. -CO- is -one
Q 10.
How do cyclic hydrocarbons differ from aromatic hydrocarbons?
Solution
Aromatic
hydrocarbons have the typical benzene ring or in other words alternate double
bonds while in cyclic hydrocarbons the terminal carbon atoms bond with each
other to form a closed cyclic structure.
Q 11.
Why is ethanol used as an additive to petrol?
Solution
Alcohol
(ethanol) is used as an additive in petrol since it is a cleaner fuel which
gives rise to only carbon dioxide and water on burning in sufficient air
(oxygen). C2H5OH + 3O2 →
2CO2 + 3H2O
Q 12.
Differentiate between addition reaction and substitution reaction shown by
hydrocarbons.
Solution
The
reactions in which an unsaturated hydrocarbon combines with simple substances
to form a single saturated product are addition reactions. Those reactions in
which one or more hydrogen of a saturated hydrocarbon is replaced by an atom or
a group of atoms are substitution reactions.
Q 13.
How ethanoic acid got its name as glacial acetic acid?
Solution
The
melting point of ethanoic acid is 290 K and hence it often freezes during
winter and forms ice like flakes.
Q 14.
(a) State the role of concentrated sulphuric acid in the esterification
reaction. (b) Write one use of esters.
Solution
(a)
Sulphuric acid being a strong dehydrating agent removes water from the reaction
mixture of ethanoic acid and ethanol. As a result, the reaction proceeds only
in the forward direction to form ester. (b) Esters are used in making
artificial perfumes.
Q 15.
Write the name and structure of an aldehyde with 5 carbon atoms.
Solution
Pentanal,
CH3CH2CH2CH2CHO
Q 16.
Define:(i) Addition reaction(ii) Substitution reaction(iii) Combustion reaction
Solution
(i)
Addition reaction:- A reaction involving addition of atoms(s) or molecules to
the double or the triple bond of an unsaturated compound to give a saturated
product is known as addition reaction.(ii) Substitution reaction:- A reaction
in which one atom of a molecule is replaced by another atom(or group of atoms)
is called a substitution reaction.(iii) Combustion reaction:- Carbon in all its
allotropic forms, burns in oxygen to give carbon dioxide and water along with
the release of heat and light. This reaction is called combustion reaction.
Q 17.
Why carbon forms strong bonds with other carbon atoms, hydrogen, oxygen,
nitrogen or sulphur?
Solution
Due
to small size and presence of four valence electrons, carbon forms strong bonds
with other carbon atoms, hydrogen, oxygen, nitrogen or sulphur.
Q 18.
Give reasons for the following: (a) Unsaturated hydrocarbons show addition
reactions but saturated hydrocarbons do not. (b) Carbon only forms covalent
compounds.
Solution
(a)
Unsaturated hydrocarbon contains either double or triple bonds, which are
reactive, so they break easily and convert into single covalent bonds hence
they easily undergo addition reactions. While saturated hydrocarbons have only
single bonds which are strong hence they do not show addition reactions. (b)
Carbon cannot lose its 4 valence electrons as large amount of energy is
required for that process. It cannot gain 4 electrons as 6 protons can't hold
10 electrons therefore, it only shares electrons to form covalent compounds.
Q 19.
What are alkanes? Name an alkane which has three carbon atoms.
Solution
Alkanes
are saturated hydrocarbons with carbon atoms bonded to each other with single
bonds. They have a general formula CnH2n+2. Propane is a
hydrocarbon with 3 carbon atoms and has the formula C3H8.
Q 20.
Name the property of carbon element responsible for a large number of compounds
having carbon. Give an example of a compound illustrating this property.
Solution
Catenation
is the property of carbon to combine with itself. Example: ethane.
Q 21.
Name the functional group present in each of the following organic compounds:
(i) CH3COCH3 (ii) C2H5COOH
Solution
(i)
Ketone (ii) Carboxylic acid
Q 22.
Write the molecular formula of cyclohexane and benzene. How are they different?
Solution
Molecular
formula : i) Cyclohexane : C6H12 ii) Benzene : C6H6
Though both contain six carbon atoms but cyclohexane is a saturated hydrocarbon and benzene is an unsaturated hydrocarbon.
Though both contain six carbon atoms but cyclohexane is a saturated hydrocarbon and benzene is an unsaturated hydrocarbon.
Q 23.
(a) What is the difference in the molecular formulae and masses of any two
adjacent homologues? (b) Separate the given compounds of same homologous
series. Name the series.
HCHO, CH3OH, C2H5CHO, C3H7OH, C2H5OH, CH3CHO
HCHO, CH3OH, C2H5CHO, C3H7OH, C2H5OH, CH3CHO
Solution
(a)
Two adjacent homologues differ by a CH2 group in their
molecular formulae. The difference in the molecular masses of any two adjacent
homologues is 14u. (b) Aldehyde homologous series - HCHO, CH3CHO,
C2H5CHO Alcohol
homologous series - CH3OH, C3H7OH, C2H5OH
Q 24.
(a) Soaps are not effective for washing woolen garments. Why?
(b) Detergents are called "soap less" soaps. Why? (c) Why
is common salt added in soap making process?
Solution
(a) Soaps
being basic in nature reacts with the acidic dyes of woolen garments and hence
are not effective for washing woolen garments. (b) Detergents are called
"soap less" soaps because though they act like soaps with
cleansing properties, they do not contain sodium stearate etc.
(c) Common salt is added in soap making process to precipitate out all the
soap from the aqueous solution.
Q 25.
Why fuels such as coal and petroleum are major pollutants in air?
Solution
Fuels
such as coal and petroleum have some amount of nitrogen and sulphur in them.
Their combustion results in the formation of oxides of sulphur and nitrogen
which are major pollutants in the environment.
Q 26.
What are oxidizing agents?
Solution
An
oxidizing agent is one which oxidizes other substances by providing oxygen or
removing hydrogen.
Q 27.
(a) Write two points of difference in the structures of diamond and graphite.
(b) Explain why, graphite can be used as a lubricant but diamond cannot.
Solution
(a)
Diamond Graphite (i) Each carbon atom is linked to four other carbon atoms.
(ii) A diamond crystal has a tetrahedral arrangement of carbon atoms. (i) Each
carbon atom is joined to only three other carbon atoms. (ii) A graphite crystal
has flat hexagonal rings structure. (b) Due to its softness, powdered graphite
can be used a lubricant whereas diamond being extremely hard cannot be used as
a lubricant.
Q 28.
Write the next higher homologue of the following: (i)C3H6 (ii)C5H8
Solution
(i)
The next higher homologue of C3H6 is C4H8.
(ii) The next higher homologue of C5H8 is C6H10.
Q 29.
Discuss the drawback of using soaps over detergents for cleansing process.
Solution
Soaps
form an insoluble substance called scum with hard water while detergent do not
form any scum with hard water. Soap reacts with the calcium and magnesium salts
which are responsible for the hardness of water to form scum. Thus, a larger
amount of soap needs to be used.
Q 30.
What is the reason for the non-biodegradable nature of detergents?
Solution
The
reason is the presence of branching in the hydrocarbon chains that are attached
to the sulphonic acid group or its sodium salt. These chains break with difficulty
by the micro-organisms that are present in sewage discharge, septic tanks or
other water bodies and make the detergents non-biodegradable.
Q 31.
How is coal formed?
Solution
Coal
is formed from biomass which has been subjected to various biological and
geological processes.
Q 32.
Give the IUPAC name of valeric acid.
Solution
Valeric
acid is saturated five carbon carboxylic acid.CH3CH2CH2CH2COOH
pentanoic acid
Q 33.
List two differences between saturated and unsaturated hydrocarbons.
Solution
Saturated
hydrocarbons Unsaturated hydrocarbons (i) Hydrocarbons have single bonds
between carbon atoms (i) Hydrocarbons have one or more multiple (double or
triple) bonds between carbon atoms. (ii) Gives a clean flame on burning. (ii)
Gives yellow flame with lots of black smoke on burning.
Q 34.
How will you distinguish between sodium chloride and carbon tetrachloride?
Solution
Sodium
chloride is an ionic compound; it is soluble in water and a good conductor
of electricity. On the other hand, carbon tetrachloride is a covalent compound;
it is insoluble in water and poor conductor of electricity.
Q 35.
What type of intermolecular force helps water and ethanoic acid to mix?
Solution
Both
in water and ethanoic acid, hydrogen bonds are present between their atoms.
Hence, they can easily form hydrogen bonds with each other.
Q 36.
Name the following compound according to IUPAC:CH3CH(OH)CH3
Solution
The
IUPAC name of this compound is propan-2-ol or 2-propanol.
Q 37.
Give the IUPAC name of the following compound. Give reasons to support your
answer.CH3CH2CH2C(=O)OH
Solution
This
compound is butanoic acid. (i) This compound has functional group -COOH, which
is a carboxylic acid, therefore suffix "-oic acid" will be used.(ii)
The carbon chain is a hydrocarbon structure with all single bonds between
carbon atoms therefore, an alkane and a suffix "-ane".(iii) The
longest continuous chain is C4 therefore, root name will be
"but-".
Q 38.
Classify following into alkanes, alkenes and alkynes: CH4, C2H2,
C4H6, C2H4, C3H6,
C2H6, C3H8, C3H4 Give
reasons.
Solution
(i)
CH4, C2H6, and C3H8 are
alkanes as they have each carbon bonded to four other atoms through single
covalent bonds and follow general formula CnH2n+2. (ii) C2H4,
C3H6 are alkenes since they contain a single
carbon-carbon double bond and follow general formula CnH2n.
(iii) C3H4, C2H2 and C4H6 are
alkynes as they contain a single carbon-carbon triple bond and follow the
general formula CnH2n-2.
Q 39.
Why do covalent compounds have low boiling and melting point?
Solution
Covalent
compounds are made up of electrically neutral molecules. So, the force of
attraction between the molecules of a covalent compound is very weak. Only a
small amount of heat energy is required to break these weak molecular forces,
due to which covalent compounds have low melting and boiling points.
Q 40.
Identify the functional group in the following compounds: (i) CH3CH2COCH3 (ii)
CH3CHO
Solution
(i)
Ketone group (or Keto group) (ii) Aldehyde group
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