Alkanes and alkenes – building and cracking formulae
carbon
1. What are the chemical symbols for the following elements?
hydrogen
2. Carbon can form two types of bonds when combining with hydrogen. Complete the table below.
Structural formula
Chemical formula
Family
General formula
Carbon to
carbon single
bonds.
Use 2 carbon
atoms and 6
hydrogen atoms.
Carbon to
carbon double
bonds.
Use 2 carbon
atoms and 4
hydrogen atoms.
3. Complete the table for the alkane family.
4. Complete the table for the alkene family.
Alkanes
Alkenes
Name
Chemical
formula
Structural formula
Name
Chemical
formula
Structural formula
methane
ethene
propane
pentene
4. Explain why there is no alkene called methene.
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Alkanes and alkenes – building and cracking formulae
The alkane family
1. Alkanes with at least 4 carbon atoms can form branched forms. These are called isomers.
An isomer of butane
Draw a branched isomer of butane
2. During the cracking process decane (which has 10 carbon atoms) can be cracked into pentane,
ethane and which alkene?
Show this equation using chemical formulae.
The alkene family
1. What is the name of the process when
alkene monomers are joined together to form
very large chains?
2. During this process, which bonds break?
3. Lots of ethane monomers to can be joined together (polymerized) to form ....................................
Complete the reaction by adding the repeating unit to show the structure of polymerised ethane.
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Alkanes and alkenes – building and cracking formulae
Answers – Page 1
1.
carbon
C
hydrogen
H
2.
Structural formula
Chemical formula
Family
General formula
Carbon to carbon
single bonds.
Use 2 carbon
atoms and 6
hydrogen atoms.
CH4
alkanes
CnH2n+2
Carbon to carbon
double bonds.
Use 2 carbon
atoms and 4
hydrogen atoms.
C2H4
alkenes
CnH2n
3.
Name
Chemical
formula
Name
Chemical
formula
Structural formula
methane
CH4
-
-
-
ethane
C2H6
ethene
C2H4
propane
C3H8
propene
C3H6
butane
C4H10
butene
C4H8
pentane
C5H12
pentene
C5H10
Structural formula
4. Alkenes have a double bond so there cannot be an alkene with just one carbon atom.
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Alkanes and alkenes – building and cracking formulae
Answers – Page 2
The alkane family
1. A structure that resembles the following:
CH3—CH—CH3
|
CH3
2. Propene
C10H22
C5H12 +
C2H6 + C3H6
The alkene family
1.
Polymerisation
2.
Carbon – carbon double bonds
3.
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