O-LevelChemistryOrganic Chemistry5070/22 · May/June 2015 · Q810 Marks

The flow chart shows the steps involved in the manufacture of poly(propenenitrile). [Figure B8.1]

(a)Long chain alkanes such as C17H36 can be cracked to form propene, C3H6. Construct an equation to show the cracking of C17H36 to form propene.[1]
(b)The equation shows the reaction to make propenenitrile. 2C3H6(g) + 2NH3(g) + 3O2(g) → 2C3H3N(g) + 6H2O(g) Describe and explain what happens to the rate of this reaction if the temperature is increased.[2]
(c)(i)The structure of propenenitrile is shown. [Figure B8.2] Explain why propenenitrile is unsaturated.[1]
(c)(ii)Describe a chemical test to show that propenenitrile is unsaturated.[2]
(d)Draw part of the structure of poly(propenenitrile).[2]
(e)A factory uses 1750 tonnes of propenenitrile to produce poly(propenenitrile). The percentage yield is 95%. Calculate the mass of poly(propenenitrile) produced.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2015). The mark or mark type is shown in brackets.

[1] (a) Any correct equation e.g. C17H36 → C3H6 + C14H30 (1)
[2] (b) reaction is faster because particles are moving faster/rate increases because particles have more energy (1)
more particles have energy above the activation energy/more effective collisions/more fruitful collisions/more energetic collisions/more (chance of) successful collisions (1)
[1] (c) (i) Has carbon-carbon double bond/has C=C bond (1)
[2] (ii) Add bromine (water) (1)
Goes from (orange/brown/red/red-brown)/to colourless/(bromine) is decolourised (1)
[2] (d) Correct repeat unit (1)
Free bonds at the end (1)
[2] (e) Maximum/predicted mass = 1750 (tonnes)
OR
1750 × 95/100 (1)
Mass of product = 1662.5 (tonnes) (1)

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