Are polyalkenes biodegradable?

No. They are chemically inert so microorganisms cannot break them down.

Are polyesters and polyamides biodegradable?

Yes. Their links can be hydrolysed.

Breaking of a bond by reaction with water, often with acid or alkali.

Why can an ester link be hydrolysed?

The carbonyl carbon is δ+, so a nucleophile such as water can attack it.

What are the products of hydrolysing a polyester?

A dicarboxylic acid and a diol (carboxylate salt in alkali).

What are the products of hydrolysing a polyamide in acid?

A dicarboxylic acid and a diammonium ion (the amine protonated).

Give two advantages of incineration with energy recovery.

Heat can generate electricity, and the volume of waste is greatly reduced.

Give one disadvantage of incineration.

Releases CO₂ and possibly toxic gases that must be removed.

Give two disadvantages of landfill.

Non-biodegradable polymers persist and it takes up land space (also wastes a chemical resource).

Give an advantage and a disadvantage of recycling.

It saves crude oil and waste; sorting and cleaning is costly and quality can fall.

What is feedstock recycling?

Breaking polymer into small molecules, such as monomers or hydrocarbons, for use as raw materials.

Which polymers suit mechanical recycling best?

A clean, single type of polymer, such as PET bottles.

Biodegradability and disposal of polymersAQA A-Level Chemistry: Flashcards

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Why are polyalkenes chemically inert?

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Why are polyalkenes chemically inert?: They contain only strong, non-polar C–C and C–H bonds, so there is no δ+ site for nucleophiles to attack.
Are polyalkenes biodegradable?: No. They are chemically inert so microorganisms cannot break them down.
Are polyesters and polyamides biodegradable?: Yes. Their links can be hydrolysed.
What is hydrolysis?: Breaking of a bond by reaction with water, often with acid or alkali.
Why can an ester link be hydrolysed?: The carbonyl carbon is δ+, so a nucleophile such as water can attack it.
What are the products of hydrolysing a polyester?: A dicarboxylic acid and a diol (carboxylate salt in alkali).
What are the products of hydrolysing a polyamide in acid?: A dicarboxylic acid and a diammonium ion (the amine protonated).
Give two advantages of incineration with energy recovery.: Heat can generate electricity, and the volume of waste is greatly reduced.
Give one disadvantage of incineration.: Releases CO₂ and possibly toxic gases that must be removed.
Give two disadvantages of landfill.: Non-biodegradable polymers persist and it takes up land space (also wastes a chemical resource).
Give an advantage and a disadvantage of recycling.: It saves crude oil and waste; sorting and cleaning is costly and quality can fall.
What is feedstock recycling?: Breaking polymer into small molecules, such as monomers or hydrocarbons, for use as raw materials.
Which polymers suit mechanical recycling best?: A clean, single type of polymer, such as PET bottles.

Exam questions on Biodegradability and disposal of polymers

A council is choosing between poly(propene) crates and polyester food trays for a school canteen. It wants to know how each material will behave if it ends up in the environment.
Explain why poly(propene) is chemically inert.2 marks
Fishing nets made from nylon-6,6, a polyamide, are sometimes lost at sea. Nylon-6,6 is made from hexanedioic acid and 1,6-diaminohexane.
The nylon-6,6 is hydrolysed by hot aqueous acid. Give the formulae of the two organic products.2 marks
A local authority collects poly(ethene) packaging waste. It can send the waste to landfill, burn it in an energy-from-waste plant, or recycle it.
State one advantage and two disadvantages of disposing of poly(ethene) waste in landfill.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).