O-LevelChemistryOrganic Chemistry5070/22 · Oct/Nov 2016 · Q810 Marks

Propenenitrile, CH2=CHCN, is made by passing a mixture of propene, ammonia and oxygen over a catalyst at 450°C. CH3CH=CH2 + NH3 + 1½O2 → CH2=CHCN + 3H2O The reaction is exothermic.

(a)Draw an energy profile diagram for this reaction on the axes shown. On your diagram label • the reactants and products, • the enthalpy change for the reaction, • the activation energy.[3]
(b)Propenenitrile decolourises aqueous bromine. Explain why.[1]
(c)The structure of propenenitrile is shown. H CN | / C = C | / H H Draw the structure of the addition polymer formed from propenenitrile.[2]
(d)(i)The catalyst used in the reaction to make propenenitrile is molybdenum. Molybdenum is a transition element. State two physical properties of molybdenum.[2]
(d)(ii)Molybdenum reacts with chlorine at room temperature to form molybdenum(VI) chloride, MoCl6. Molybdenum(VI) chloride has a melting point of 254°C. Construct an equation for this reaction, including state symbols.[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 (Oct/Nov 2016). The mark or mark type is shown in brackets.

[1] reactants labelled on left and products labelled on the right AND product level below reactant level
[1] enthalpy change labelled and shown by downward arrow
[1] activation energy shown as upward arrow from left hand energy level to energy 'hump' above the highest energy levels of both products and reactants
[1] C=C double bond/it is unsaturated
[1] CN CH - CH2
[1] extension bonds shown
[1] high melting point/high boiling point
[1] high density
[1] hard
[1] good conductor of electricity/good conductor of heat
[1] malleable
[1] ductile
[1] shiny/lustrous
[1] correct formulae (Mo(s) + 3Cl2(g) → MoCl6 (s))
[1] correct state symbols, dependent on correct formulae

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