O-LevelChemistryRates of Reaction5070/22 · May/June 2016 · Q910 Marks

Carbon monoxide reacts with hydrogen in a reversible reaction. CO(g) + 2H2(g) ⇔ CH3OH(g) ∆H = −91 kJ/mol The reaction reaches an equilibrium if carried out in a closed container.

(a)Explain, in terms of bond breaking and bond forming, why this reaction is exothermic.[2]
(b)When one mole of methanol, CH3OH, is formed, 91 kJ of energy is released. Calculate the amount of energy released when 160 g of methanol is formed. [Mᵣ of methanol = 32] energy released = .................................................... kJ[2]
(c)(i)Predict, with a reason, how the position of equilibrium of this reaction changes as the pressure is increased at constant temperature,[2]
(c)(ii)temperature is increased at constant pressure.[2]
(d)(i)Methanol and compound X react together to form methyl butanoate. Name X.[1]
(d)(ii)The reaction is normally carried out using a catalyst. Name a suitable catalyst for this reaction.[1]

Mark scheme

Marking points from the official mark scheme (May/June 2016). The mark or mark type is shown in brackets.

[1] Bond breaking absorbs energy AND bond making releases energy/bond breaking is endothermic AND bond making is exothermic
[1] Less energy absorbed than released/more energy released than absorbed/endothermic energy change is less than exothermic energy change/exothermic energy change is more than endothermic energy change
[1] Moles of methanol = 5
[1] Energy released = 455 kJ
[1] Position of equilibrium moves to the right/equilibrium shifts to the product side
[1] Fewer moles on product side/more moles on reactant side/greater volume (of gas) on left ORA/greater number of molecules on the left ORA
[1] Position of equilibrium moves to the left/equilibrium shifts to the reactant side
[1] Reaction is exothermic/forward reaction is exothermic/backward reaction is endothermic
[1] Butanoic acid
[1] (Mineral) acid

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