Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Biodegradable polyesters
18 practice questions
Practice questions
1–8 of 8 · Normal
Question 1
2 marks · Normal
Answer and see the solution →State the two types of functional groups present in lactic acid that allow it to form a biodegradable polyester.
Question 2
4 marks · Normal
Answer and see the solution →Biodegradable polyesters such as PLA can be broken down by environmental processes more easily than many other polymers.
(a)[1 mark]Explain what is meant by the term 'ester linkage' in a polyester.
(b)[3 marks]Describe why polyesters with ester linkages are more biodegradable than addition polymers.
Question 3
3 marks · Normal
Answer and see the solution →Lactic acid has the molecular formula . A single lactic acid molecule is used as the monomer for making polylactic acid (PLA).
Calculate the molecular formula of the repeat unit of PLA, given that one molecule of water () is eliminated each time two lactic acid monomers link. Show your working.
Question 4
4 marks · Normal
Answer and see the solution →The table shows the time taken for different types of polymers to degrade in soil:
Degradation times of polymers in soil Polymer Degradation time (months) PLA (polylactic acid) 12 Poly(ethene) 400 Poly(ester) 18 Poly(propene) 350 Use the data to answer the questions.
(a)[1 mark]Which polymer is the most biodegradable? Give the evidence from the table.
(b)[3 marks]Explain, using your knowledge of chemical structure, why PLA degrades faster than poly(ethene) or poly(propene).
Question 5
1 mark · Normal
Answer and check →Which of the following shows the correct displayed formula for the repeat unit of polylactic acid (PLA)?
- A.—[O—CH(CH3)—CO]—
- B.—[CH2—CH(OH)—CO]—
- C.—[O—CH2—CO]—
- D.—[CH(OH)—CH3—COO]—
Question 6
2 marks · Normal
Answer and see the solution →Describe how polylactic acid (PLA) is produced from its monomer, lactic acid.
Question 7
4 marks · Normal
Answer and see the solution →Polyesters are condensation polymers that are more biodegradable than many addition polymers.
(a)[1 mark]State what is meant by a condensation polymerisation reaction.
(b)[3 marks]With reference to chemical bonding, explain why polyesters can be biodegraded more easily than addition polymers.
Question 8
3 marks · Normal
Answer and see the solution →Lactic acid has the formula . When making a biodegradable polyester such as polylactic acid (PLA), lactic acid monomers react with each other to form a long polymer chain.
Explain, using your knowledge of its structure, how lactic acid can form a biodegradable polyester like PLA from a single type of monomer.