Ammonia Chemical Bonding Worksheet Page 25
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28(c)
(from the graph) the best yield is obtained at high pressure;
and low temperature;
it is a reversible reaction;
in which formation of ammonia is favoured at low temperature
(because) the reaction is exothermic;
and the formation of ammonia is favoured at high pressure
because greater number of gaseous reactant molecules than
gaseous product molecules/because greater vol of reactant
than volume of product molecules;
pressure used is limited by cost/materials;
rate of reaction slow at low temperatures;
actual temperature and pressure used is a good compromise
(between a good yield and reasonable rate);
removal of ammonia makes rate more important than yield;
any 8 for 1 mark each
8
[12]
M8.
(a)
(i)
idea that it is
a reaction in which the products can themselves react to reform the
original substance or a reaction that can go in either direction
(allow explanation in terms of the specific reaction in the question)
for 1 mark
1
(ii)
nitrogen, hydrogen and ammonia
(allow formulae)
for 1 mark
1
(b)
(i)
high pressure/400 atm
low temperature/100 °C
for 1 mark each
2
(ii)
higher rate of reaction
good rate of production
or idea that more economic (ally viable)
(allow catalyst more effective at higher temperature)
for 1 mark each
2
(c)
(i)
ideas that it involves
use of catalyst
gains 1 mark
but use of platinum catalyst
gains 2 marks
2
high temperature/900 °C
for 1 mark
1
Page 25 of 28
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