Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Biodegradable polyesters
18 practice questions
Practice questions
1–7 of 7 · Easy
Question 1
1 mark · Easy
Answer and see the solution →Draw the structure of the repeat unit of polylactic acid (PLA) formed from lactic acid monomers.
Question 2
3 marks · Easy
Answer and see the solution →Lactic acid, which contains both a carboxylic acid group and an alcohol group in its molecule, can be used to make a biodegradable polyester.
(a)[1 mark]State the two functional groups present in lactic acid that allow it to form a polyester.
(b)[2 marks]Describe how a polyester such as PLA can be formed from lactic acid monomers.
Question 3
1 mark · Easy
Answer and see the solution →State the type of chemical bond in the backbone of PLA that makes it more biodegradable than poly(ethene).
Question 4
3 marks · Easy
Answer and see the solution →Polylactic acid (PLA) is formed by joining multiple lactic acid units.
(a)[1 mark]Draw the displayed formula of lactic acid.
(b)[2 marks]Show (with a labelled diagram or description) how two lactic acid molecules join to form an ester linkage.
Question 5
2 marks · Easy
Answer and see the solution →Polyesters such as polylactic acid (PLA) are more biodegradable than most addition polymers.
Calculate the number of ester linkages in a PLA chain formed from 10 lactic acid monomers. Show your working.
Question 6
2 marks · Easy
Answer and see the solution →Lactic acid () is the monomer for the biodegradable polyester called PLA (polylactic acid).
Draw the displayed (structural) formula for a section of the polylactic acid (PLA) polymer, showing two repeat units joined together.
Question 7
3 marks · Easy
Answer and see the solution →Lactic acid is a monomer that can be used to make the biodegradable polyester polylactic acid (PLA). The data table below shows three monomers, the type of polymerisation they can undergo, and whether the resulting polymer is biodegradable.
Monomer Type of polymerisation Is the polymer biodegradable? Lactic acid Condensation Yes Ethene Addition No Hexanedioic acid and ethane-1,2-diol Condensation Yes Analyse the table and answer the following parts:
(a)[1 mark]State which monomer from the table is used to make PLA.
(b)[1 mark]Based on the table, what type of polymerisation is used to make PLA?
(c)[1 mark]Use the data to give one reason why polylactic acid (PLA) is considered environmentally friendly.