Synthetic Polymers

5 marks · Easy

The polymer poly(propene) is produced by the addition polymerisation of propene.

(a)

Draw the displayed formula of the repeat unit of poly(propene).

[2 marks]

(b)

Write the displayed formula of the monomer used to make poly(propene).

[1 mark]

(c)

How many propene molecules would be needed to form a polymer chain containing 3000 carbon atoms?

[2 marks]

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) [—CH2—CH(CH3)—] · must show Two carbon backbone with one CH3 and four H attached as in displayed formula

(b) CH2=CHCH3 (propene) · must show Displayed formula, double bond present

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · Correct displayed structure of the poly(propene) repeat unit (backbone with two carbons; continuation bonds shown).

B2 (a) · 1 mark · Correct side group (CH3) and correct number of hydrogens on each carbon in the repeat unit.

B3 (b) · 1 mark · Correct displayed formula or structural formula for propene (must show C=C).

M1 (c) · 1 mark · Identifies that each monomer adds 2 carbons to the chain.

A1 (c) · 1 mark · Correct division and answer: 1500 propene molecules needed for 3000 carbons.

Worked solution

a) The repeat unit of poly(propene) has the following structure:

b) The monomer is propene, with structural formula CH2=CHCH3 or displayed as:

c) Each propene contains 3 carbons, but only 2 join the backbone in polymerisation. For a chain with 3000 carbons in the backbone:

So, 1500 propene molecules are needed.