Topic 6 – Hydrocarbons – Q and A
1 What are the alkanes?
A family of hydrocarbons
2 Which of the following are alkanes:
ethene, propyne, butane, ethanol,
decane, propene?
butane and decane because they end in
-ane
3 Name the first 8 alkanes. (If you
don't remember them they are in the
data book).
methane, ethane, propane, butane,
pentane, hexane, heptane, octane
(nonane, decane)
4 Give uses for: a) methane b)
propane c) butane d) octane
methane – cookers, heating
propane: portable heaters
butane – lighter fuel
octane – petrol
5 Name the following alkanes:
CH4, C5H12, C7H16, C3H8
methane, pentane, heptane, propane
6 What is the general formula of the
alkanes?
CnH2n+2
7 Work out the molecular formula of
the alkanes with:
a) 2 carbons b) 6 carbons c) 8
carbons
C2H6
C6H14
C8H18
8 Which of the following are alkenes:
ethene, propyne, butane, ethanol,
decane, propene?
ethene and propene (end in –ene)
9 Name the first 5 alkenes.
ethene, propene, butene, pentene,
hexene
10
Name the following alkenes:
C2H4, C6H12, C5H10, C3H6
ethene, hexene, pentene, propene
11
What is the general formula of
the alkenes?
CnH2n
12
Work out the molecular
formula of the alkenes with:
a) 2 carbons b) 6 carbons c) 8 carbons
C2H4, C6H12, C8H16
13
Draw molecular formulae and
full structural formulae for the
following hydrocarbons:
C2H4
C4H10
ethene, ethane, butane, pentene
1
C2H6
C5H10
Topic 6 – Hydrocarbons – Q and A
14
What is meant by a saturated
hydrocarbon?
A hydrocarbon with single bonds only
between carbons
16
What is meant by an
unsaturated hydrocarbon?
A hydrocarbon with at least one C=C
double bond
17
Which of the following are
saturated:
ethane, ethene, propane,
butene?
ethane and propane are saturated
(alkanes have single bonds)
18
What chemical test is used to
distinguish between a saturated
and an unsaturated
hydrocarbon? State the result
of the test.
Bromine water when added to an
unsaturated hydrocarbon is
decolourised quickly.
19
State the type of reaction that
occurs between bromine and an
unsaturated hydrocarbon.
Addition reaction.
20
Does fractional distillation of
crude oil give adequate supplies
of short chain hydrocarbons for
uses such as petrol.
No it gives too much of the less useful
bigger molecules.
21
What is the name of the
industrial method for producing
smaller, more useful
molecules?
Catalytic cracking or thermal cracking.
22
In what 2 ways are the products
of cracking different from the
original molecules?
The molecules are smaller and lighter.
Alkenes are always produced.
2
Topic 6 – Hydrocarbons – Q and A
Credit Questions
1
What is meant by a homologous series?
A family of related compounds with similar
properties.
Alkanes, alkenes (also cycloalkanes)
2
Give 2 examples of homologous series.
3
What is the general formula of
a) the alkanes
b) the alkenes
4
The first three members of a homologous
series are:
C2H2, C3H4, C4H6
What is the general formula of this series?
5
Name the first five members of the
cycloalkanes.
cyclopropane, cyclobutane, cyclopentane,
cyclohexane, cycloheptane
6
Explain what is meant by isomers.
Molecules with same molecular formula and
different structural formulae.
7
Draw extended structures for 2 isomers
with the formula
a) C4H10
b)
C5H12
8
Explain why the boiling point increases
steadily as we go from methane to octane.
The molecules are getting bigger and so are
harder to separate – more energy needed.
9
In thermal cracking, why does use of a
catalyst represent a cost saving?
Less heat is needed using a catalyst, so energy
is saved.
CnH2n+2
CnH2n-2
a)
10 What types of molecules are produced
from the cracking of long chain alkanes?
b)
Smaller molecules always including alkenes.
12 Copy and complete this equation for
cracking putting in numbers for x and y
and suggest possible names for all the
products.
C10H22 
CnH2n
C3H6
Butane, propene and propene
C4H10 + C3H6 + CxHy
(one of the propenes might be
cyclopropane)
3