O-LevelChemistryRates of Reaction5070/21 · Oct/Nov 2015 · Q1010 Marks

Methanol is manufactured by reacting carbon monoxide with hydrogen. The forward reaction is exothermic. CO(g) + 2H2(g) ⇌ CH3OH(g) ΔΗ = – 91 kJ/mol

(a)Predict and explain the effect of increasing the pressure on the position of equilibrium. The temperature remains constant.[2]
(b)Predict and explain the effect of decreasing the temperature on the position of equilibrium. The pressure remains constant.[2]
(c)The rate of reaction decreases when the temperature is lowered. Explain why.[2]
(d)(i)The reaction is catalysed by copper. Describe and explain the effect of a catalyst on this reaction.[2]
(d)(ii)Copper is a transition element. Many transition elements are catalysts. Give two other properties of copper that identify it as a transition element.[2]

Mark scheme

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

[2] B10(a) position of equilibrium moves to right/more products formed (1) goes in direction of decreasing number of moles/goes in direction of smaller volume/fewer moles of products than reactants (1)
[2] (b) position of equilibrium goes to the right/more products formed (1) reaction is exothermic/backward reaction is endothermic/reaction goes to the exothermic direction (1)
[2] (c) particles move slower/particles have less energy (1) fewer particles have activation energy/fewer successful collisions/fewer fruitful collisions (1)
[2] (d) (i) speeds up reaction (1) by lowering the activation energy/providing an alternative reaction pathway (1)
[2] (ii) ANY TWO FROM: form coloured compounds (1) have variable oxidation states/form ions with different charges (1) form complex ions (1)

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.