Chemistry · Oct / Nov 2016 · Paper 22 · Question B7
5070
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The question as text
B7 In the contact process, sulfur trioxide is made by the catalytic oxidation of sulfur dioxide. In a closed container the following equilibrium is set up. 2SO2(g) + O2(g) 2SO3(g) The reaction is exothermic.
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B7(a)[1]
vanadium pentoxide/vanadium(V) oxide/V2O5 (1)
1
B7(b)[1]
four bonding electrons between the two oxygen atoms AND four non-bonding electrons on each oxygen atom (1)
1
B7(c)(i)[3]
little/no change in % yield at low temperature (1)
yield decreases as temperature increases (1)
reaction is exothermic so equilibrium moves to the left as temperature increases/increasing temperature favours the endothermic reaction (1)
3
B7(c)(ii)[2]
at 250 °C reaction is slow(er)/at 450 °C reaction is fast(er) (1)
idea of compromise temperature/idea of balance between lower yield and faster rate (1)
2
B7(d)[2]
(position of) equilibrium moves to the right/(position of) equilibrium moves towards the product side (1)
more (gas) molecules on left than right of the equation/fewer (gas) molecules on right of equation than left (1)
2
B7(e)[1]
SO3 + 2HBr → SO2 + Br2 + H2O (1)
1 Total: 10
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