Q1.
Ammonia Ammonia is used in the production of fertilisers. The flow diagram shows the main stages in the manufacture of ammonia. Study the flow diagram and then answer the questions.
(a)
What is the purpose of the iron in the reactor? ........................................................................................................................ ........................................................................................................................ (1)
(b)
In the reactor the equation to produce ammonia is
! (g) "
(i)
#
$% (g) "
"!% (g) $
The equation shows that the reaction is re&ersible. 'plain how the reaction reaches an equilibrium. ...............................................................................................................
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............................................................................................................... (1)
(ii)
The best yield of ammonia at equilibrium is produced at a low temperature. 'plain why. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... (2)
(iii)
The best yield of ammonia at equilibrium is produced at a high pressure. 'plain why. ............................................................................................................... ............................................................................................................... (1) (Total 5 marks)
Q2.
Ammonia is made from nitrogen and hydrogen in the %aber process. ! (g) # $% (g) "
"
"!% (g) (# heat) $
Flow Chart for the Haber Process
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'ffect of temperature and pressure on t he amount of ammonia at equilibrium
(a)
+se the information gi&en abo&e and your ,nowledge of the %aber process and re&ersible reactions to help you to answer t his question. State which conditions of temperature and pressure would gi&e the highest
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percentage of ammonia at equilibrium. 'plain why. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (4)
(b)
The %aber process uses a temperature of -/ 01 and a pressure of "// atmospheres. 'plain why these conditions are chosen. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 7 marks)
Q3.
'arly atmospheres on 'arth contained ammonia (!% ). $
(a)
(i)
1omplete the sentence. 2ur atmosphere today is made up of about ...................... ........ 3 nitrogen. (1)
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(ii)
Today we con&ert nitrogen bac, to ammonia mainly for the production of fertilisers. What do plants con&ert the nitrogen in these fertilisers into? ........................................................................................................................... ........................................................................................................................... (1)
(b)
The con&ersion of nitrogen to ammonia is shown.
(i)
When ma,ing ammonia4 what is one source of hydrogen? ........................................................................................................................... (1)
(ii)
Apart from ammonia4 name one other product formed during this con&ersion. ........................................................................................................................... (1)
(c)
The main reaction is the formation of ammonia from nitrogen and hydrogen. (i)
1omplete and balance the equation for this reaction. .......................(g) # .......................(g) 5 .........!% (g) $
(2)
(ii)
!ame the metal catalyst used in this reaction. ...........................................................................................................................
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(1)
(iii)
This reaction does not wor, successfully at room temperature ("/ 01) and needs a much higher temperature of -// 01. 'plain why. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
(d)
6raw a diagram to show the arrangement of the electrons in a molecule of ammonia. The electron arrangement of each atom is hydrogen * and nitrogen ". .
(2) (Total 11 marks)
Q4.
Ammonia is produced by the %aber process. In the process nitrogen and hydrogen are mied. The pressure is increased to about "// atmospheres. The gases are passed o&er an iron catalyst at about -/01. The equation for the reaction is ! (g) "
#
$% (g) "
"!% (g) $
The reaction between nitrogen and hydrogen is re&ersible. This affects the amount of ammonia that it is possible to obtain from the process. The graph below shows how the pressure and temperature affect the percentage of ammonia that can be produced.
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+se this information4 together with your ,nowledge of the process4 to eplain why many industrial ammonia plants operate at "// atmospheres and -/01. ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... (Total 5 marks)
Q5.
The flow chart below shows the main stages in the production of ammonium nitrate.
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(a)
(i)
!ame the two raw materials shown in the flow chart as and !. 9aw material ........................................................ 9aw material ! ........................................................ (2)
(ii)
What is the purpose of the iron in the reactor? ............................................................................................................................ ............................................................................................................................ (1)
(b)
(i)
:alance the equation which represents the reaction which produces ammonia in the %aber process.
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! # ...................... % "
"
...................... !% and heat $
(1)
(ii)
The table shows how temperature and pressure affect the amount of ammonia produced in this reaction.
T'<'9AT+9' (01)
9'SS+9' (AT<) '91'!TA=' 2> !IT92='! A!6 %692='! 12!@'9T'6 T2 A<<2!IA (3)
"/
"//
8
"/
*///
7
*///
*
/./*
*///
*///
*
'plain4 as fully as you can4 why a temperature of about -/01 and a pressure of about "// atmospheres are normally used in the industrial process. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ (") (Total 1# marks)
Q".
(a) Ammonia is manufactured from nitrogen and hydrogen. The equation for the reaction between them is
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! (g) # $% (g) "
(i)
"
"!% (g) $
What is the source of the nitrogen? ........................................................................................................................... (1)
(ii)
Why does increasing the pressure increase the chance of molecules of hydrogen reacting with molecules of nitrogen? ........................................................................................................................... ........................................................................................................................... (1)
(iii)
The percentage yield of ammonia is the percentage4 by mass4 of the nitrogen and hydrogen which has been con&erted to ammonia. 1alculate the mass4 in tonnes4 of ammonia which can be produced from / tonnes of hydrogen when the percentage yield is /3. The relati&e atomic masses are % *B ! *-. Show clearly how you get to your answer. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................
(b)
The percentage yield of ammonia depends on the temperature and pressure inside the reaction &essel. The set of graphs show this.
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(i)
<a is the symbol for which unit? ........................................................................................................................... (1)
(ii)
What is the percentage yield of ammonia produced at a temperature of -/ 01 and a pressure of "/ <a? ........................................................................................................................... (1)
(iii)
Suggest what changes the chemical engineers should ma,e to both the temperature and the pressure to $ncrease the percentage yield of ammonia. Temperature ..................................................................................................... ressure ............................................................................................................ (1)
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(i&)
%ow can the rate of ammonia production be increased without changing the temperature or pressure or the mass of hydrogen and nitrogen? ........................................................................................................................... ........................................................................................................................... (1)
(c)
About fourDfifths of ammonia production is used to produce fertilisers. 2ne of them is ,nown as !E. It is made in the following way. F F F F
Some ammonia is con&erted to nitric acid which is then mied with phosphoric acid. The miture is neutralised with more ammonia and the solution is partly e&aporated. otassium chloride is added to form granules. The granules are coated to ma,e the fertiliser freeDflowing.
1omplete the flowDchart for the production of !E by writing in the names of the correct chemicals in the s$% boes.
(2) (Total 1# marks)
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Q7.
Ammonia is manufactured from nitrogen and hydrogen. The reaction is shown in the equation below.
The diagram shows some details of the manufacturing process.
The graph shows the percentage of reacting gases con&erted into ammonia at different temperatures and pressures.
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At room temperature and pressure4 the reaction is &ery slow and only a small percentage of the reacting gases is con&erted to ammonia. +se the information on the diagram and graph to
(a)
describe the conditions used in the manufacture of ammonia to $ncrease the rate of react$on. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (4)
(b)
describe and eplain the conditions used in the manufacture of ammonia to $ncrease the &$el'. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................
..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................
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..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (7) (Total 11 marks)
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