Addition polymerisation

5 marks · Hard

Describe how poly(ethene) is prepared in the chemical industry.

(a)

State the name and formula of the monomer used to make poly(ethene).

[1 mark]

(b)

Write the equation for the polymerisation reaction, using displayed formulae for both the monomer and the polymer's repeat unit, and including 'n' notation.

[2 marks]

(c)

State the type of reaction used to produce poly(ethene).

[1 mark]

(d)

Describe the essential conditions needed for this reaction.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) Ethene,

(b) · must show Displayed formula for monomer: H2C=CH2, Repeat unit of polymer in displayed formula, with extension bonds and 'n' notation

(d) Heat, high pressure, and an initiator are needed · must show Heat and high pressure, Mention of initiator (not catalyst)

Common mistakes: Failing to use displayed formulae in the equation; Missing the 'n' in the equation; Incorrect reaction type (e.g., writing 'condensation' instead of 'addition'); Not stating both heat and high pressure for conditions

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · States ethene and gives formula

M1 (b) · 1 mark · Writes correct reactant and product structures in displayed formulae, includes extension bonds and 'n' notation

A1 (b) · 1 mark · Correct balancing of the polymerisation equation, using brackets and subscript 'n' for the polymer

B2 (c) · 1 mark · States reaction is addition polymerisation

B3 (d) · 1 mark · States correct conditions: heat, high pressure, and initiator (not catalyst)

Worked solution

a) The monomer is ethene, formula .

b) The equation is:

(Displayed formulae as below: )

c) This is an addition polymerisation reaction.

d) The reaction needs high temperature, high pressure, and an initiator to start the process.