c3 yield and atom economy name: of chemical reactions · this question is about zinc and magnesium....

C3 YIELD AND ATOM ECONOMYOF CHEMICAL REACTIONSQuestion Practice

Name: ________________________

Class: ________________________

Date: ________________________

Time: 95 minutes

Marks: 94 marks

Comments: GCSE CHEMISTRY ONLY

Page 1 of 37Immanuel+College

Magnesium reacts with steam to produce hydrogen gas and magnesium oxide.

A teacher demonstrated the reaction to a class. The figure below shows the apparatus theteacher used.

(a) (i) The hydrogen produced was collected.

Describe how to test the gas to show that it is hydrogen.

Test __________________________________________________________

______________________________________________________________

Result ________________________________________________________

______________________________________________________________

(2)

1

(ii) Explain why the magnesium has to be heated to start the reaction.

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)


(b) The equation for the reaction is:

Mg(s) + H2O(g) MgO(s) + H2(g)

(i) The teacher used 1.00 g of magnesium.

Use the equation to calculate the maximum mass of magnesium oxide produced.

Give your answer to three significant figures.

Relative atomic masses (A r): O = 16; Mg = 24

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

Maximum mass = ____________________ g

(3)

(ii) The teacher’s demonstration produced 1.50 g of magnesium oxide.

Use your answer from part (b)(i) to calculate the percentage yield.

If you could not answer part (b)(i), use 1.82 g as the maximum mass of magnesiumoxide. This is not the answer to part (b)(i).

______________________________________________________________

Percentage yield = ____________________ %

(2)

(iii) Give one reason why the percentage yield is less than 100%.

______________________________________________________________

______________________________________________________________

______________________________________________________________

(1)

(Total 10 marks)


This question is about zinc and magnesium.

Zinc is produced by electrolysis of molten zinc chloride, as shown in the figure below.

(a) (i) Why must the zinc chloride be molten for electrolysis?

______________________________________________________________

______________________________________________________________

(1)

2

(ii) Describe what happens at the negative electrode.

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(3)

(iii) Complete the half equation for the reaction at the positive electrode.

________ Cl2 + ________ e–

(1)

(b) Magnesium can be produced from magnesium oxide.

The equation for the reaction is:

Si(s) + 2 MgO(s) SiO2(s) + 2 Mg(g)

(i) How can you tell from the equation that the reaction is done at a high temperature?

______________________________________________________________

______________________________________________________________

(1)


(ii) This reaction to produce magnesium from magnesium oxide is endothermic.

What is meant by an endothermic reaction?

______________________________________________________________

______________________________________________________________

(1)

(iii) A company made magnesium using this reaction.

Calculate the mass of magnesium oxide needed to produce 1.2 tonnes ofmagnesium.

Relative atomic masses (Ar): O = 16; Mg = 24

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

Mass of magnesium oxide needed = ____________________ tonnes

(3)

(iv) The company calculated that they would produce 1.2 tonnes of magnesium, but only0.9 tonnes was produced.

Calculate the percentage yield.

______________________________________________________________

______________________________________________________________

Percentage yield = __________ %

(1)

(v) Give one reason why the calculated yield of magnesium might not be obtained.

______________________________________________________________

______________________________________________________________

(1)

(Total 12 marks)


The symbol equation for the decomposition of hydrogen peroxide is:

2H2O2 → 2H2O + O2

(a) This reaction is exothermic.

What is an exothermic reaction?

___________________________________________________________________

___________________________________________________________________

(1)

3

(b) A student measured the volume of oxygen produced by 50 cm3 of hydrogen peroxide.


The graph shows the results.

(i) Use the graph to describe the changes in the rate of the reaction from 0 to 35seconds.

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(3)

(ii) What was the total volume of oxygen gas collected?

________________________ cm3

(1)

(iii) The student had calculated that the hydrogen peroxide used shouldproduce 25 cm3 of oxygen.

Calculate the percentage yield of oxygen.

______________________________________________________________

______________________________________________________________

______________________________________________________________

Answer = ________________ %

(2)


(c) An increase in the temperature of the hydrogen peroxide increases the rate of the reaction.

Use your knowledge of particles to explain why.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

(3)

(Total 10 marks)

A student investigated the reactions of copper carbonate and copper oxide with dilutehydrochloric acid.

In both reactions one of the products is copper chloride.

(a) Describe how a sample of copper chloride crystals could be made from copper carbonateand dilute hydrochloric acid.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

(4)

4


(b) A student wanted to make 11.0 g of copper chloride.

The equation for the reaction is:

CuCO3 + 2HCl → CuCl2 + H2O + CO2

Relative atomic masses, Ar: H = 1; C = 12; O = 16; Cl = 35.5; Cu = 63.5

Calculate the mass of copper carbonate the student should react with dilute hydrochloricacid to make 11.0 g of copper chloride.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Mass of copper carbonate = _________________________ g

(4)

(c) The percentage yield of copper chloride was 79.1 %.

Calculate the mass of copper chloride the student actually produced.

___________________________________________________________________

___________________________________________________________________

Actual mass of copper chloride produced = ____________ g

(2)


(d) Look at the equations for the two reactions:

Reaction 1 CuCO3(s) + 2HCl(aq) → CuCl2(aq) + H2O(l) + CO2(g)

Reaction 2 CuO(s) + 2HCl(aq) → CuCl2(aq) + H2O(l)

Reactive formula masses: CuO = 79.5; HCl = 36.5; CuCl2 = 134.5; H2O = 18

The percentage atom economy for a reaction is calculated using:

Calculate the percentage atom economy for Reaction 2.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Percentage atom economy = ________________________ %

(3)

(e) The atom economy for Reaction 1 is 68.45 %.Compare the atom economies of the two reactions for making copper chloride.

Give a reason for the difference.

___________________________________________________________________

___________________________________________________________________

(1)

(Total 14 marks)


The graph in Figure 1 shows a flow diagram for the Haber process.

Figure 1

(a) (i) Hydrogen gas is obtained from methane.Name one source of methane.

____________________________________

(1)

5

(ii) Air is the source used to produce nitrogen for the Haber process.Suggest why air must not get into the reactor.

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)

(iii) Describe what happens to the mixture of gases from the reactor.

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(3)


(b) The graph in Figure 2 shows the percentage yield of ammonia using different conditions.

Figure 2

(i) Use Figure 2 to suggest the conditions that produce the greatest yield of ammonia.

______________________________________________________________

______________________________________________________________

(1)


(ii) Use Figure 2 to suggest and explain why the conditions used to produce ammonia inthe Haber process are a temperature of 450 °C and a pressure of 200 atmospheres.

______________________________________________________________

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(5)

(Total 12 marks)


Ammonium sulfate and urea are made from ammonia. These compounds are used by farmers.

The flow diagram shows the stages to make ammonium sulfate and urea.

(a) Give two examples from the flow diagram of the efficient use of energy and raw materials.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

(2)

6


(b) The equation for the reaction in Stage 4 is shown below.

N2(g) + 3H2(g) 2NH3(g)

The forward reaction is exothermic.

State and explain:

(i) how a decrease in temperature would affect the yield of ammonia at equilibrium

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)

(ii) how an increase in pressure would affect the yield of ammonia at equilibrium.

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)


(c) The equation for the reaction in Stage 7 is shown below.

2 NH3ammonia

+ CO2NH2CONH2

urea+ H2O

The table gives the relative formula masses (Mr) of the reactants and the products for thisreaction.

Formula of reactant or product Relative formula masses (Mr)

NH3 17

CO2 44

NH2CONH2 60

H2O 18

Percentage atom economy can be calculated using:

Calculate the percentage atom economy for the reaction in Stage 7.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Percentage atom economy = ____________________________ %

(2)

(Total 8 marks)

Percentage atom economy =


Aspirin tablets have important medical uses.

7

A student carried out an experiment to make aspirin. The method is given below.

1. Weigh 2.00 g of salicylic acid.2. Add 4 cm3 of ethanoic anhydride (an excess).3. Add 5 drops of concentrated sulfuric acid.4. Warm the mixture for 15 minutes.5. Add ice cold water to remove the excess ethanoic anhydride.6. Cool the mixture until a precipitate of aspirin is formed.7. Collect the precipitate and wash it with cold water.8. The precipitate of aspirin is dried and weighed.

(a) The equation for this reaction is shown below.

C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH salicylic acid aspirin

Calculate the maximum mass of aspirin that could be made from 2.00 g of salicylic acid.

The relative formula mass (Mr) of salicylic acid, C7H6O3, is 138

The relative formula mass (Mr) of aspirin, C9H8O4, is 180

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Maximum mass of aspirin = _______________ g

(2)


(b) The student made 1.10 g of aspirin from 2.00 g of salicylic acid.

Calculate the percentage yield of aspirin for this experiment.

(If you did not answer part (a), assume that the maximum mass of aspirin that can bemade from 2.00 g of salicylic acid is 2.50 g. This is not the correct answer to part (a).)

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Percentage yield of aspirin = _______________ %

(2)

(c) Suggest one possible reason why this method does not give the maximum amount ofaspirin.

___________________________________________________________________

___________________________________________________________________

(1)

(d) Concentrated sulfuric acid is a catalyst in this reaction.

Suggest how the use of a catalyst might reduce costs in the industrial production of aspirin.

___________________________________________________________________

___________________________________________________________________

(1)

(Total 6 marks)


The Haber process is named after the German chemist, Fritz Haber.

The diagram shows the main stages in the Haber process.

Reproduced with the permission of Nelson Thornes Ltd from PATRICK FULLICK et al,

ISBN 0-7487-9644- 4. First published in 2006

An exothermic reaction takes place when nitrogen reacts with hydrogen to make ammonia.

The reaction can be represented by this equation.

N2 (g) + 3H2 (g) 3

8

2NH (g)

(a) Calculate the maximum mass of ammonia that could be made from 1000 g of nitrogen.

Relative atomic masses: H = 1; N = 14

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Mass _______________g

(3)


(b) At a temperature of 450 °C and 200 atmospheres the actual mass of ammonia producedwhen 1000 g of nitrogen is passed through the reactor is 304 g.

Calculate the percentage yield of ammonia produced in the reactor.

(If you did not answer part (a), then assume that the maximum mass of ammonia that canbe made from 1000 g of nitrogen is 1100 g. This is not the correct answer to part (a).)

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

Percentage yield of ammonia = _______________ %

(2)

(c) State and explain:

(i) how a decrease in temperature would affect the yield of ammonia

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)

(ii) how an increase in pressure would affect the yield of ammonia.

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

(2)


(d) Factories that make ammonia are often near to large towns.

Discuss the economic, safety and environmental factors to be considered when there is anammonia factory near a town.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

(3)

(Total 12 marks)

(a) Ammonia is manufactured from nitrogen and hydrogen. The equation for the reactionbetween them is:

N2(g) + 3H2(g) 3(g)

9

2NH

(i) What is the source of the nitrogen?

______________________________________________________________

(1)

(ii) Why does increasing the pressure increase the chance of molecules of hydrogenreacting with molecules of nitrogen?

______________________________________________________________

______________________________________________________________

(1)

(iii) The percentage yield of ammonia is the percentage, by mass, of the nitrogen andhydrogen which has been converted to ammonia. Calculate the mass, in tonnes, ofammonia which can be produced from 90 tonnes of hydrogen when the percentageyield is 50%. The relative atomic masses are: H 1; N 14.

Show clearly how you get to your answer.

______________________________________________________________

______________________________________________________________

______________________________________________________________

Mass = ________________________ tonnes

(2)


(b) The percentage yield of ammonia depends on the temperature and pressure inside thereaction vessel. The set of graphs show this.

(i) MPa is the symbol for which unit?

______________________________________________________________

(1)

(ii) What is the percentage yield of ammonia produced at a temperature of 450 °C and apressure of 20 MPa?

______________________________________________________________

(1)

(iii) Suggest what changes the chemical engineers should make to both the temperatureand the pressure to increase the percentage yield of ammonia.

Temperature ___________________________________________________

Pressure ______________________________________________________

(1)


(iv) How can the rate of ammonia production be increased without changing thetemperature or pressure or the mass of hydrogen and nitrogen?

______________________________________________________________

______________________________________________________________

(1)

(c) About four-fifths of ammonia production is used to produce fertilisers. One of them is knownas NPK. It is made in the following way.

• Some ammonia is converted to nitric acid which is then mixed with phosphoric acid.• The mixture is neutralised with more ammonia and the solution is partly evaporated.• Potassium chloride is added to form granules.• The granules are coated to make the fertiliser free-flowing.

Complete the flow-chart for the production of NPK by writing in the names of the correctchemicals in the six boxes.

(2)

(Total 10 marks)


Mark schemes

(a) (i) lit splint or ignite the gas11

(squeaky) pop / explosion1

(ii) because it provides energy (for the reaction)1

to break bonds (in the reactants) or so the particles collide successfully

ignore reference to frequency or rate of collisions

because it provides the activation energy gains 2 marks1

(b) (i) 1.67(g)

allow 1.66-1.68

correct answer (to 3 significant figures) with or without workinggains 3 marks

if answer incorrect allow up to 2 marks for the following steps:

24 → 401.00 → 40 / 24or

moles magnesium = 1 / 24 or 0.04(17)

multiply by 40

allow ecf from incorrect ratio or incorrect number of moles3

(ii) if correct answer from part (b)(i) used

allow ecf from part (b)(i)

89.8 or 90

if 1.82 g used

82.4 or 82

correct answer with or without working gains 2 marks

if answer incorrect, allow the following for 1 mark:

1.50 / 1.67 (or their answer from part (b)(i))

if 1.82 g used: 1.50 / 1.822


(iii) any one from:

ignore measurement errors

• not all the magnesium reacted

allow the reaction may be reversible• some of the magnesium oxide / product may have been left in the tube or

may have been lost

ignore magnesium lost• different / unexpected reaction• magnesium not pure

1

[10]


(a) (i) so ions can move (and carry charge)

accept so current can flow

allow so it can conduct (electricity)

allow so charged particles can move

do not accept so electrons can move1

(ii) because zinc ions gain electrons

accept because zinc ions are reduced1

2 (electrons)1

zinc is formed

accept correct half equation for 3 marks

if no mark gained allow

positive ions go to negative electrode or

opposites attract or

reduction (of zinc) or

(zinc) gains electrons for 1 mark1

(iii) 2 Cl– Cl2 + 2 e–

must be completely correct1

(b) (i) because the magnesium is a gas

allow magnesium goes from solid to gas1

(ii) (a reaction which) takes in energy (from the surroundings)

accept more energy needed to break bonds than released byforming bonds

accept correct reference to energy level diagram

allow (a reaction which) takes in heat (from the surroundings)1

(iii) (Mr MgO =) 40

accept (2 Mr MgO =) 801

1.2 / 24 (x40) or 0.05 (x40)

or

40 / 24 (x1.2) or 1.67 (x1.2)

allow ecf from step 11

2(.0)

2


allow ecf carried through from step 1

correct answer with or without working gains 3 marks1

(iv) 75(%)1

(v) any one from:• the reaction is reversible

accept incomplete reaction

ignore equilibrium not reached• some lost / escaped / released (when separated)• some of the reactant may react in different ways from the expected

reaction• impure reactant(s)

ignore measurement and calculation errors1

[12]

(a) gives out energy or heat13

(b) (i) accept qualified answers in terms of volume of gas related to time

fast initially1

slows down1

reaction stops

accept reaction is now very slow1

(b) (ii) 211

(iii) 84

correct answer with or without working = 2 marks

allow ecf from (b)(ii) correctly calculated for 2 marks

allow evidence of 21/25 or (b)(ii)/25 for 1 mark2

(c) because they / particles have more energy / move faster

ignore particles move more / vibrate1

(and so) particles collide more often / more frequently or particles more likely to collide

ignore collide faster

ignore more collisions1


(and) more of the collisions are successful or particles collide with more energy / harder ormore of the particles have the activation energy

accept more successful collisions1

[10]

(a) add excess copper carbonate (to dilute hydrochloric acid)

accept alternatives to excess, such as ‘until no more reacts’1

4

filter (to remove excess copper carbonate)

reject heat until dry1

heat filtrate to evaporate some water or heat to point of crystallisation

accept leave to evaporate or leave in evaporating basin1

leave to cool (so crystals form)

until crystals form1

must be in correct order to gain 4 marks

(b) Mr CuCl2 = 134.5

correct answer scores 4 marks1

moles copper chloride = (mass / Mr = 11 / 134.5) = 0.08178438661

Mr CuCO3= 123.51

Mass CuCO3 (=moles × M2= 0.08178 × 123.5) = 10.1(00)1

accept 10.1 with no working shown for 4 marks

(c)

or

11.0 × 0.7911

8.70 (g)1

accept 8.70(g) with no working shown for 2 marks

(d) Total mass of reactants = 152.51


134.5

152.5

allow ecf from step 11

88.20 (%)1

allow 88.20 with no working shown for 3 marks

(e) atom economy using carbonate lower because an additional product is made or carbondioxide is made as well

allow ecf1

[14]

(a) (i) natural gas

allow fossil fuels / biogas generator1

5

(ii) air contains oxygen1

this would react with / oxidise the hydrogen

allow this would react with / oxidise the iron

ignore nitrogen1

(iii) cooled1

ammonia condenses / liquefies (so can be separated)1

nitrogen and hydrogen (remain as gases and) are returned to the reactor

allow recycled1

(b) (i) 200 °C and 1000 atmospheres1

(ii) the reaction is reversible

allow stated as equilibrium or forward / backward reaction anywherein answer

1

forward reaction is exothermic so increased temperature lowers the yield of ammonia

allow converse1

a lower temperature would decrease rate of reaction

allow converse1


a higher pressure would increase the yield of ammonia because the forward reactionproduces the least number of (gaseous) molecules / moles

allow converse1

higher pressures would involve high cost / energy1

ignore risk / explosion

[12]

(a) any two from:

• heat water / make steam / boil water or heat / steam used in stage 1 or fromstage 3

• carbon dioxide from stage 3 used in stage 7 /to make urea

• nitrogen and / or hydrogen recycled

• ammonia and / or carbon dioxide recycled

allow unreacted material / gas recycled from stage 5 (to 4)

allow unreacted material / gas recycled from stage 8 (to 7)

NB: if neither of the last two points are awarded unreacted materialrecycled = 1 mark

2

6

(b) (i) increase yield

because (forward) reaction is exothermic

ignore references to rate1

allow because (forward) reaction gives out heat1

(ii) increase yield

ignore references to rate1

because more (gaseous) reactant molecules than (gaseous) product molecules

accept because greater volume on the left than the right1


(c) 76.9 - 77

correct answer gains 2 marks with or without workingallow 77 or 76.923…

allow 76 or 0.77 or 0.76923 for 1 mark

if answer incorrect allow 1 mark for either

or

2

[10]

x 100

x 100

(a) 2.61 / range 2.5 to 2.7

correct answer with or without or with wrong working gains 2 marks

(accept answers between 2.5 and 2.7)

if answer incorrect moles of salicylic acid = 2/138 = 0.0145 molesie 2/138 or 0.0145 gains 1 markor(180/138) × 2 gains 1 markor1 g → 180/138 = (1.304 g) gains 1 mark(not 1.304g alone)

2

7

(b) 42.1 range 40.7 to 42.3

accept correct answer with or without or with wrong working for 2marks

ecf ie (1.1 / their answer from (a)) × 100 correctly calculated gains 2marks

if answer incorrect percentage yield = 1.1 / 2.61 × 100 gains 1 mark

if they do not have an answer to part (a)orthey choose not to use their answer then:

• yield = (1.1 / 2.5) × 100 (1)

• = 44

accept 44 for 2 marks with no working2


(c) any one from:

• errors in weighing

• some (of the aspirin) lost

do not allow ‘lost as a gas’

• not all of the reactant may have been converted to product

eg reaction didn’t go to completion

allow loss of some reactants

• the reaction is reversible

accept other products / chemicals

• side reactions

ignore waste products

• reactants impure

• not heated for long enough

• not hot enough for reaction to take place1

(d) any one from:

• use lower temperature

• use less fuel / energy

ignore references to use of catalyst

• produce product faster or speed up reaction

• more product produced in a given time (owtte)

• increased productivity

• lowers activation energy1

[6]


(a) 1213.8 to 1214.3

gains 3 marks without working

correct answer not given then check working

1) moles of N2 =

1 mark for each correct step

do not penalise rounding errors in this part

2) moles of NH3 = 2 × (answer from (1)) = 71.4 mol

3) mass of NH3 = (answer from 2) × 17 = 71.4 × 17 = 1214 g3

8

= 35.7 mol

or

• 28g of N 2 → 34g of NH31 mark for each correct step

• 1g of N 2 → 3

do not penalise rounding errors in this part

• 1000 g of N 2 → 1000 × 1.214 = 1214g

allow error carried forward eg

= 1.214g NH

or

• 1000 ×

gains 2 marks if correct answer not given

1000 ×

(823.5g) 1000 × calculated correctly (1647.05g)

gains 1 mark, 2 marks if correctly calculated

gains 1 mark if or

other correct methods

look for the key ideas in the methods above


(b) 25 / 25.035 or ecf from (a)

gains 2 marks even when there is no working

incorrect answer then 304/(their answer from (a)) × 100 gains 1mark

or using figures from part (b)

27.6 / 28

gains 2 marks even when there is no working

accept 27 for 1 mark

if answers incorrect then304/1100 × 100 gains 1 mark2

(c) (i) increase yield1

reaction is exothermic

or

allow decreased yield because rate of reaction is slower /fewer collisions for 2 marks

must get both points for 2 marks1

(ii) increase yield1

plus one from:

• more (gaseous) reactant molecules than (gaseous)product molecules (owtte)

accept greater volume on the left than the right owtte

• increased rate of reaction / more collisions1


(d) any one from:

economic

• large town provides workforce

• workers do not have to travel far to the factory. (owtte)

• transport infrastructure already in place for large town. (owtte)

• factory brings prosperity to town (owtte)

• factory provides employment

• reduced tourism

• reduction in local house prices

• any other sensible economic factor linked to town1

any one from:

safety

• escape of dangerous / harmful chemicals / gases (owtte)

do not allow polluting gases unqualified

• danger of increased traffic

• risk of explosion.(owtte) /danger of high pressure

• consequences of an accident could be severe if the town is close

• any other sensible safety idea1


any one from:

environmental

• factory might be unsightly (owtte)

• screening of factory (owtte)

• loss of habitats (owtte)

• plant trees/ hedges etc on and around plant site

• pollution of water / air / soil could harm plants / animals or noise pollution

must be explained

• CO 2 is produced by burning fuels / heating

• CO 2 causes global warming / any effect of global warming

• eye sore

• any other sensible environmental factor1

[12]

(a) (i) atmosphere

or (fractional distillation of liquid) air1

(ii) eithermore (chance) of them colliding/

not just ‘faster’

coming into contactorthe volume of the product / the ammonia is less than /only half the volume of the reactants / the nitrogen and hydrogen

1

9

(iii) 3 × (1 ×2) of hydrogen→ 2 × (14 +1 ×3) of ammonia

accept 6 parts of hydrogen →34 parts of ammonia or similari.e. candidate uses the atomic masses and works correctly from theequation

1

= 225 (tonnes/t)

unit not required1


(b) (i) megapascal(s)

accept million pascal(s)1

(ii) 28 (%)

accept any answer in the range 28.0 to 28.5 inclusive1

(iii) reduce the temperature and increase the pressure

both required1

(iv) eitheruse a catalyst

accept use iron as a catalyst

accept use iron which has been more finely divided

accept use iron / catalyst with a bigger (surface) area

accept use a better catalyst1

orremove the ammonia (as it is produced)

accept react the ammonia with or dissolve the ammonia in water(as it is produced)

1

(c) ammonianitric acidphosphoric acid

all three on the left correct

ammonia potassium chloride

all three on the right correct

water or water vapour

accept ‘steam’1

[10]


c3 yield and atom economy name: of chemical reactions · this question is about zinc and magnesium....

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