Addition polymerisation

2 marks · Easy

A segment of the addition polymer poly(propene) contains 40 repeat units. Each repeat unit has the formula . Calculate the relative molecular mass (Mr) of this portion of the polymer. (Relative atomic masses: C = 12, H = 1)

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1680 (±0)

Common mistakes: Calculating Mr of a single repeat unit only; Incorrect multiplication

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Marking points

M1 · 1 mark · Correctly calculates relative molecular mass (Mr) of one repeat unit: (3 x 12) + (6 x 1) = 42

A1 · 1 mark · Multiplies Mr of repeat unit by 40: 42 × 40 = 1680

Worked solution

Relative molecular mass (Mr) of is calculated as:

For 40 repeat units: