Download Unit 2 - Nat 5 Homework 1

Uddingston Grammar School
National 5 Chemistry
Hydrocarbons and Homologous Series
Unit 2 sub-unit b. Homework 1
1. Which of the following could be the molecular formula of a cycloalkane?1KU
A.
B.
C.
D.
C6H8
C6H10
C6H12
C6H14
2. The name of the compound below is
A.
B.
C.
D.
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But – 2 – ene
Pent – 2 – ene
But – 3 – ene
Pent – 3 - ene
3. Which of the following compounds is not an isomer of pent–1–ene?
A.
B.
C.
D.
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But – 1 – ene
Pent – 2 – ene
Cyclopentane
2 – methylbut – 1 - ene
4. The balanced equation for the complete combustion of a hydrocarbon X is
shown below.
X(g)
+
2O2(g)

CO2(g)
+
Which of the following is the correct formula of hydrocarbon X?
A.
B.
C.
D.
CH4
C2H6
C3H8
C4H10
2H2O(l)
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5. Which of the following structures belongs to the same homologous series as
the compound with the formula C3H8
1PS Selecting
6. Which of the following is an isomer of heptane?
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7.
The name of the above compound is
A.
B.
C.
D.
2,2-dimethylbutane
2-ethylpropane
2-methylbutane
3-methylbutane.
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Section 2
8. The lowest temperature at which a hydrocarbon ignites is called its flash
point.
Hydrocarbon
Hexane
Heptane
Octane
Nonane
Flash point
(oC)
-23
-4
13
31
a) Using the information in the table, make a general statement linking
the flash point to the number of carbon atoms.
1PS Predicting
b) Predict the flash point, in °C, of decane, C10H22.
1PS Analysing
9. The octane number of petrol is a measure of how efficiently it burns as a
fuel.
The higher the octane number, the more efficient the fuel.
The octane numbers for some hydrocarbons are shown.
Hydrocarbon
Butane
Pentane
Hexane
Heptane
Octane
2-methylpentane
2-methylhexane
2-methylheptane
Number of carbon atoms
4
5
6
7
8
6
7
8
a) Predict the octane number for hexane.
Octane number
90
62
0
-19
71
44
23
1 PS Predicting
b) State a relationship between the structure of the hydrocarbon and
their efficiency.
1 PS Processing
c) One of the hydrocarbons in the table above is 2-methylhexane. Draw
the full structural formula of 2-methylhexane.
1KU
10. Liquefied petroleum gas (LPG), which can be used as a fuel for heating, is a
mixture of propane and butane.
Propane and butane are members of the homologous series of alkanes.
a) State the number of the two boxes that correctly describe members
of the same homologous series.
1 KU
1.
2.
3.
4.
5.
They have
They have
They have
They have
They have
similar chemical properties.
the same molecular formula.
the same general formula.
the same physical properties.
the same formula mass.
b) The table gives some information about propane and butane.
Alkane
Propane
Butane
Boiling Point
(oC)
-42
-1
Explain why butane has a higher boiling point than propane.
2 KU
c) State the general formula for the alkanes and the name of the 3rd
member of the alkanes.
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15 Marks