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Draw structures to show the differences that occur in the bonding in three ethene molecules when they undergo addition polymerisation and become part of a poly(ethene) chain - Leaving Cert Chemistry - Question B - 2017
Question B
Draw structures to show the differences that occur in the bonding in three ethene molecules when they undergo addition polymerisation and become part of a poly(ethen... show full transcript
Worked Solution & Example Answer:Draw structures to show the differences that occur in the bonding in three ethene molecules when they undergo addition polymerisation and become part of a poly(ethene) chain - Leaving Cert Chemistry - Question B - 2017
Step 1
Draw structures to show the differences that occur in the bonding in three ethene molecules when they undergo addition polymerisation and become part of a poly(ethene) chain.
Answer
The structures of three ethene molecules can be described as follows:
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The first structure represents three ethene molecules ( H H H | | | C = C + C = C + C = C | | |
H H H) -
The polymerisation process converts the double bonds into single bonds, forming a poly(ethene) chain:
H H H | | | C - C - C | | |
H H H -
As the reaction continues, long chains are formed such as:
H H H H | | | | ... - C - C - C - C - ... | | | |
H H H H
This shows the differences in bonding structures resulting from the polymerisation of ethene.
Step 2
Give two differences in properties, other than the difference in density, between LDPE or low-density poly(ethene) and HDPE or high-density poly(ethene).
Answer
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LDPE is more branched, which contributes to its lower melting point and shorter chain length, making it softer and more flexible compared to HDPE, which has a more linear structure and higher density.
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HDPE is stronger and less flexible, exhibiting higher tensile strength compared to LDPE.
Step 3
What were the differences between the conditions used for the production of LDPE and HDPE?
Answer
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LDPE is produced under higher pressures and lower temperatures compared to HDPE, which is produced under lower pressures and higher temperatures.
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The catalyst used for the production of LDPE is typically organometallic (Ziegler-Natta catalyst), while HDPE also utilizes similar catalysts but with different formulations.