REACTIONS AND PROPERTIES OF ALKANES
Graded Worksheet
PHYSICAL PROPERTIES
Below is a table with the boiling points of the first 8 straight chain alkanes:ALKANE
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
FORMULA
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
B.P (OC)
- 164
- 88
- 42
- 0.5
36
69
98.5
125.8
B.P (K)
109
185
231
272.5
309
342
371.5
398.8
1) Plot a graph, either by hand or using Excel, to show how the boiling point of the alkanes
(on the y-axis) varies with the number of C atoms in the molecule (on the x-axis). You may
use boiling points in either units – whichever you prefer.
If you are using Excel, this should be an x-y scatter graph and you should select the form
with a smoothed line joining the points. If you are doing a hand-drawn graph, draw the best
smooth curve through the points afterwards.
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2) Describe how the boiling point changes with the number of C atoms in the molecule.
Explain the trend in boiling points by considering the intermolecular forces present between
alkane molecules.
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COMBUSTION
3) Alkanes are hydrocarbons and will burn. When hydrocarbons burn in plenty of air, there are
only two products, carbon dioxide and water.:a) Write a balanced chemical equation for the complete combustion of propane.
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b) Write a balanced chemical equation for the complete combustion of octane.
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c) What environmental problem arises from the carbon dioxide formed from the burning of
fossil fuels?
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4) 1 mole of an alkane requires 11 moles of oxygen for complete combustion. Deduce which
alkane this is and write a balanced chemical equation for the reaction.
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5) When there is a limited oxygen supply, then the hydrocarbons are incompletely burnt. Soot
and carbon monoxide form instead of carbon dioxide. Describe the problems associated
with these two products of incomplete combustion.
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SUBSTITUTION REACTIONS
6) When chlorine reacts with an excess of methane in ultraviolet light, chloromethane is formed
as the main organic product.
a) Write a balanced equation for the reaction forming chloromethane.
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b) Give the name of the mechanism for the formation of chloromethane and then outline it,
including the name for each of the three stages in the reaction.
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7) Although chloromethane is the main organic product in the reaction above, there are other
products formed. Give the names and formula of two other organic compounds, one
containing chlorine and one not containing chlorine, which might be present in the mixture at
the end of the reaction. Explain how each of these products has been formed.
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