Download End of chapter exercises

End of chapter exercises
Problem 1:
Give one word or phrase for each of the following descriptions:
1. The name of the homologous series to which 2-methylpropene belongs.
2. The name of the functional group that gives alcohols their properties.
3. The group of organic compounds that have acidic properties.
4. The IUPAC name of the organic compound that is found in vinegar.
5. The name of the organic compound that is found in alcoholic beverages.
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Answer 1:
1. Alkenes
2. Hydroxyl group
3. Carboxylic acid
4. Ethanoic acid
5. Ethanol
Problem 2:
When 1-propanol is oxidised by acidified potassium permanganate, the possible product
formed is:

propane

propanoic acid

methyl propanol

propyl methanoate
(IEB 2004)
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Answer 2:
propanoic acid
Problem 3:
What is the IUPAC name for the compound represented by the following structure?

1,2-dichlorobutane

2,2-dichlorobutane

1,2-dichloro-3-methylpropane

1,1-dichloro-3-methylpropane
(IEB 2003)
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Answer 3:
1,2-dichlorobutane
Problem 4:
Give the structural representation and IUPAC name of all possible isomers for C6H14 (hint:
there are 5)
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Answer 4:
Problem 5:
Write balanced equations for the following reactions:
1. Ethene reacts with bromine (use condensed structural representations)
2. The complete combustion of ethyne gas (used molecular formula)
3. Ethanoic acid ionises in water
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Answer 5:
1. CH2CH2+Br2 → CH2(Br)CH2(Br)
ethene + bromine → 1,2-dibromoethane
2. 2C2H2(g)+5O2(g) → 4CO2(g)+2H2O(g)
3. CH3COOH(ℓ)+H2O(ℓ) → CH3COO−(aq)+H3O+(aq)
Problem 6:
The table below gives the boiling point of ten organic compounds.
Compound
Molecular formula
Boiling Point (°C)
CH4
1
−162
methane
C2H6
2
−89
ethane
C3H8
3
propane
4
butane
5
pentane
−42
C4H10
0
C5H12
36
CH4O
6
methanol
64,7
C2H6O
7
ethanol
78,4
C3H8O
8
propan-1-ol
97
C3H8O2
9
propan-1,2-diol
10
propan-1,2,3-triol
188
C3H8O3
290
Table 1
The following questions refer to the compounds shown in the above table.
1. Which of the above compounds are gases at room temperature?
2. What is the reason for the trend of increasing boiling points seen in compounds 1 to 5?
3. Despite the fact that the length of the carbon chain in compounds 8,9 and 10 is the
same, the boiling point of propan-1,2,3-triol is much higher than the boiling point of
propan-1-ol. What is responsible for this large difference in boiling point?
4. Give the IUPAC name and the structural representation of an isomer of butane.
5. Which one of the compounds is used as a reactant in the preparation of the ester ethyl
methanoate?
6. Using structural representation, write an equation for the reaction which produces ethyl
methanoate.
(IEB 2004)
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Answer 6:
1. Methane, ethane, propane and butane (i.e. compounds 1 - 4)
2. As the alkanes increase in chain length so does their surface area. This leads to
stronger intermolecular forces and an increase in boiling point.
3. As each hydroxyl group is added the strength of the intermolecular forces increases.
The compound can form more hydrogen bonds. This leads to an increase in the boiling
point.
4. 2-methylpropane
5. Ethanol (7)
6.
Problem 7:
Refer to the numbered diagrams below and then answer the questions that follow.
1. Which one of the above compounds is produced from the fermentation of starches and
sugars in plant matter?
2. To which one of the following homologous series does compound 1 belong?
1. esters
2. alcohols
3. aldehydes
4. carboxylic acids
3. The correct IUPAC name for compound 3 is...
1. 1,1-dibromobut-3-yne
2. 4,4-dibromobut-1-yne
3. 2,4-dibromobut-1-yne
4. 4,4-dibromoprop-1-yne
4. What is the correct IUPAC name for compound 4?
1. propanoic acid
2. ethyl methanoate
3. methyl ethanoate
4. methyl propanoate
IEB 2005
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Answer 7:
1. compound 2, ethanol
2. iv) carboxylic acids
3. ii) 4,4-dibromobut-1-yne
4. iii) methyl ethanoate
Problem 8:
Answer the following questions:
1. Explain the term homologous series.
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Answer 8:
1. A homologous series is a series of compounds with the same general formula. All
molecules in this series will contain the same functional groups. For example the
alkanes are a homologous series: they have the general formula CnH2n+2; for
every extra carbon atom there are two extra hydrogen atoms.
Problem 9:
Consider the organic compounds labelled A to D.
A. CH3CH2CH2CH2CH2CH3
B. C6H6
C. CH3−Cl
D.
1. Write a balanced chemical equation for the preparation of compound C using an
alkane as one of the reactants.
2. Write down the IUPAC name for compound D.
3. Write down the structural representation of an isomer of compound A that has only
FOUR carbon atoms in the longest chain.
4. Write down the structural representation of compound B.
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Answer 9:
1. CH4+Cl2+light → CH3Cl+HCl
2. There are six carbon atoms in the longest chain containing the functional group so the
prefix is hex-. The compound is a ketone and the ketone carbon is the second carbon
atom, so the suffix is -2-one. There are 2 methyl groups attached to the fourth carbon
atom (4,4-dimethyl). The compound is 4,4-dimethylhexan-2-one.
3. The molecular formula of compound A is C6H14.
Note that these are the only two possibilities.
4.
or
or
Any one of the above structures is reasonable. Learners can also draw benzene.
Problem 10:
Chlorine and ethane react to form chloroethane and hydrochloric acid.
1. Write a balanced chemical equation for this reaction, using molecular formulae.
2. Give the structural representation of chloroethane.
3. What type of reaction has taken place in this example?
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Answer 10:
1. Cl2(g)+C2H6(g)+light → C2H5Cl(g)+HCl(ℓ)
2.
3. Substitution
Problem 11:
Petrol is in fact not pure C8H18 but a mixture of various alkanes. The octane rating of petrol
refers to the percentage of the petrol which is C8H18. For example, 93 octane fuel contains
93% C8H18 and 7% other alkanes. The isomer of C8H18 referred to in the octane rating is
in fact not octane but 2,2,4-trimethylpentane.
1. Write a balanced equation for the chemical reaction which takes place
when C8H18 burns in excess oxygen (complete combustion).
2. Give the general formula of the alkanes.
3. Define the term isomer.
4. Use the information given in this question and your knowledge of naming organic
compounds to deduce and draw the full structural formula for 2,2,4trimethylpentane.(I.E.B.)
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Answer 11:
1. 2C8H18(ℓ)+25O2(g) → 16CO2(g)+18H2O(g)+heat
2. CnH2n+2
3. Isomers are two (or more) organic compounds that have the same molecular formula
but a different structural formula.
4.