Topic 20: Polymerisation

Question 1

Definitions I:
(a) Addition polymerisation
(b) Repeat unit
(c) Monomer

Answer 1

Definitions I:
(a) Monomers with C=C join without byproducts, forming a polymer.
(b) Smallest repeating segment of a polymer chain, e.g., -CH₂CH₂-.
(c) Small molecule that polymerises, e.g., CH₂=CH₂.

Question 2

Write the polymerisation equation for ethene forming poly(ethene). [2 Marks]

Answer 2

n CH₂=CH₂ → [-CH₂CH₂-]ₙ (1 mark)
Poly(ethene) forms (1 mark)

Question 3

Deduce the repeat unit for poly(chloroethene) from CH₂=CHCl. [2 Marks]

Answer 3

CH₂=CHCl → [-CH₂CHCl-]ₙ (1 mark)
Repeat unit: -CH₂CHCl- (1 mark)

Question 4

In a factory, propene is polymerised. Identify the monomer from [-CH(CH₃)CH₂-]ₙ. [2 Marks]

Answer 4

[-CH(CH₃)CH₂-]ₙ from CH₂=CHCH₃ (1 mark)
Monomer: propene (1 mark)

Question 5

Why is disposal of poly(ethene) problematic in landfills? [2 Marks]

Answer 5

Non-biodegradable, resists breakdown (1 mark)
Accumulates in landfills, long-term pollution (1 mark)

Question 6

Describe the process of addition polymerisation using poly(ethene) as an example. [3 Marks]

Answer 6

Ethene’s C=C opens, bonds form (1 mark)
Chain grows via addition, no byproducts (1 mark)
Forms [-CH₂CH₂-]ₙ, poly(ethene) (1 mark)

Question 7

In a lab, CH₂=CHCl forms PVC. Write the equation and name the polymer. [2 Marks]

Answer 7

n CH₂=CHCl → [-CH₂CHCl-]ₙ (1 mark)
Poly(chloroethene), PVC (1 mark)

Question 8

What harmful products arise from burning poly(chloroethene) in waste incineration? [2 Marks]

Answer 8

HCl gas, toxic chlorine compounds (1 mark)
Pollutes air, harms health (1 mark)

Question 9

Deduce the repeat unit for a polymer made from CH₂=CHCH₃. [2 Marks]

Answer 9

CH₂=CHCH₃ → [-CH(CH₃)CH₂-]ₙ (1 mark)
Repeat unit: -CH(CH₃)CH₂- (1 mark)

Question 10

In recycling, why can’t poly(alkene)s biodegrade naturally? [2 Marks]

Answer 10

Stable C-C bonds, no natural degradation (1 mark)
Microbes can’t break poly(alkene)s (1 mark)

Question 11

Identify the monomer in this polymer section: [-CH₂-CHCl-CH₂-CHCl-] and write its formula. [2 Marks]

Answer 11

Monomer: CH₂=CHCl (1 mark)
From [-CH₂CHCl-], chloroethene (1 mark)

Question 12

Compare the environmental impact of poly(ethene) vs. poly(chloroethene) disposal. [3 Marks]

Answer 12

Both non-biodegradable, persist in environment (1 mark)
Poly(ethene): CO₂ on burning, less toxic (1 mark)
Poly(chloroethene): HCl, more harmful (1 mark)