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The outer layers of some golf balls are made from a polymer called polystyrene - AQA - A-Level Chemistry - Question 3 - 2019 - Paper 2
Question 3
The outer layers of some golf balls are made from a polymer called polystyrene. The isoprene monomer is a non-cyclic branched hydrocarbon that contains 88.2 % carbon... show full transcript
Worked Solution & Example Answer:The outer layers of some golf balls are made from a polymer called polystyrene - AQA - A-Level Chemistry - Question 3 - 2019 - Paper 2
Step 1
Deduce the molecular formula and suggest a possible structure.
Answer
To deduce the molecular formula from the empirical formula of isoprene, we can use the information provided:
- The empirical formula has 88.2% carbon, which gives us a ratio of carbon to hydrogen.
- The molecular formula can be deduced using the empirical formula:
Empirical formula: C₅H₈.
Thus, the molecular formula for isoprene is C₅H₈.
A possible structure for isoprene is as follows:
H H
\ /
C=C
/ \
H C
/ \
H H
This shows that isoprene is a branched hydrocarbon with a double bond.
Step 2
Draw the skeletal formula of the monomer used to make this polymer.
Answer
The skeletal formula of the monomer used to make this polymer, which has the repeating unit shown in the question, is:
H H
\ /
H - C - C - H
/ \
H H
This structure represents the branch points and hydrogen atoms in the polymer.
Step 3
Step 4
Step 5
Give a reason why this type of stereoisomerism arises.
Answer
This type of stereoisomerism arises due to the presence of a double bond (C=C), which restricts rotation around the bond, leading to different spatial arrangements of the atoms or groups attached to the carbons involved in the double bond. This creates geometric (cis/trans) isomerism.
Step 6
Explain why these golf balls do not biodegrade.
Answer
Golf balls do not biodegrade due to the presence of resilient polymers like polystyrene in their construction. The carbon-carbon bonds in these polymers are strong and resistant to breakdown by microbial action, hence they persist in the environment over extended periods.