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AQA GCSE · Question 06.1 · Organic chemistry
Disposable cups are made from coated paper or poly(styrene). Figure 4 represents the structure of poly(styrene). Which small molecule is used to produce poly(styrene)?
Disposable cups are made from coated paper or poly(styrene). Figure 4 represents the structure of poly(styrene). Which small molecule is used to produce poly(styrene)?
Answer options:
A.
Ethene
B.
Styrene
C.
Propene
D.
trans-1,2-diphenylethene
How to approach this question
1. Look at the repeating unit of the polymer poly(styrene) shown in Figure 4. The backbone is -C-C- and the groups attached are C₆H₅, H, H, and H.
2. Polymerisation involves breaking a C=C double bond in a small molecule (the monomer) to form a long single-bonded chain.
3. To find the monomer, mentally "reverse" this process: turn the single C-C bond in the backbone back into a C=C double bond and keep the attached groups the same.
4. Compare this structure with the options provided.
Full Answer
B.Styrene✓ Correct
The second option: Styrene monomer
Poly(styrene) is an addition polymer. It is formed from many small monomer molecules joining together. The name "poly(styrene)" tells us the monomer is called styrene.
The structure of the polymer shows a repeating unit: `[-CH(C₆H₅)-CH₂-]`.
This repeating unit is formed when the double bond in the styrene monomer breaks. The styrene monomer must therefore have a C=C double bond and the same groups attached to the carbon atoms.
The structure of the styrene monomer is `CH(C₆H₅)=CH₂`. This matches the second option provided.
Common mistakes
✗ Choosing the monomer for a different polymer, like ethene.
✗ Being confused by the different chemical groups attached to the carbon atoms.
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