Edexcel GCSE Chemistry

Topic Questions

GCSEChemistryEdexcelTopic Questions5. Separate Chemistry 15.3 Dynamic Equilibria

5.3 Dynamic Equilibria

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1a1 mark

Ammonia is produced in a reversible reaction from hydrogen and nitrogen during the Haber process. 

Write the word equation for this reaction.

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1b1 mark

Which statement is not true about the Haber process for making ammonia?

☐ A Platinum is used as a catalyst
☐ B The process is carried out at a temperature of about 450 oC
☐ C The process takes place at a pressure of about 200 atmospheres
☐ D Natural gas is a raw material

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1c1 mark

Higher Only 

What does the graph show about the effect of pressure and temperature on the Haber process?

10-4

☐ A Less ammonia is produced at higher pressures
☐ B The yield of ammonia decreases with increased temperature
☐ C The optimum conditions are low pressure and high temperature
☐ D At 500 atmospheres and 400 °C the yield of ammonia is 45%

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1d1 mark

Higher Only

Why is a lower temperature than 450 °C not used during the Haber process?

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2a1 mark

Fertilisers are used to increase the yield of crops. 

Name the elements found in an NPK fertiliser.

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2b1 mark

Ammonium nitrate is a common fertiliser.

Write the word equation for the production of ammonium nitrate. 

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2c1 mark

A student was preparing a sample of ammonium sulfate in the lab. 

The steps they carried out are written below. 

The steps shown are not in the correct order. 

 step J  Heat the solution to partially evaporate the water  
 step K  Add sulfuric acid into a burette noting the starting volume 
 step L  Leave the remaining solution to dry and crystallize 
 step M  Determine the volume of sulfuric acid added and repeat the titration without indicator
 step N  Add the sulfuric acid to the ammonia slowly until the indicator changes colour  
 step O  Add ammonia into a conical flask with some indicator 

Write the steps in the correct order. 

Some of the steps have been completed for you. 

 first step                    last step
O                   L

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2d2 marks

Ammonium nitrate can be prepared industrially and on a smaller scale in a lab. 

Place ticks in boxes by two disadvantages of making ammonium nitrate on an industrial scale. 

The process is fast  
 It is an expensive process   
 Large concentrations of fertiliser are produced   
 There are several stages involved   
 Low concentrations of fertiliser are produced  

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3a2 marks

The Haber process produces ammonia which can be used as fertiliser. 

Balance the symbol equation for the Haber process. 

N2    +   ___H2   rightwards harpoon over leftwards harpoon   ___NH3

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3b1 mark

In the reaction in part a) the forward reaction is exothermic, 

Complete the missing word. 

The reverse reaction in the Haber process is ________________.

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3c3 marks

Higher Only

The conditions for the Haber process can be altered to achieve a high yield of ammonia. 

Use the words from the box to complete the sentences about why a a temperature of 450 oC is used. 

exothermic middle right fast
left high endothermic slow

At low temperatures, the _________________ reaction is favoured. 

The equilibrium shifts to the ____________  to produce more ammonia. 

At low temperatures the rate of reaction is ____________. 

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3d1 mark

Higher Only

An iron catalyst is used in the Haber process. 

Why is a catalyst used?

  ☐ A To produce more ammonia
  ☐ B To use less energy 
  ☐ C To reduce the rate of reaction
  ☐ D To use less hydrogen and nitrogen 

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4a1 mark

The Haber process produces ammonia from nitrogen and hydrogen.

N2    +  3H2   →   2NH3

How many atoms are there in one molecule of ammonia?

  ☐ A 2
  ☐ B 3
  ☐ C 4
  ☐ D 5

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4b2 marks

The nitrogen and hydrogen atoms in ammonia are joined by covalent bonds. 

This involves the sharing of electrons. 

Complete the dot and cross diagram for ammonia. 

You only need to show the outer shell electrons.

dot-and-cross-ammonia-incomplete

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4c4 marks

When nitrogen and hydrogen react to form ammonia, the reaction can reach a dynamic equilibrium.

Put ticks (✔) in the boxes to show which statements are true and which statements are false. 

The first one has been done for you. 

  true false
 The nitrogen and hydrogen no longer react   ✔
 The concentrations of the reactants and products remains constant    
 The rate of the forward reaction is equal to the rate of the reverse reaction    
 The reaction is no longer reversible     
 The concentration of reactants and products is the same    

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4d1 mark

Dynamic equilibrium takes place in a closed system. 

What is meant by a closed system?

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5a1 mark

The ammonia produced in the Haber process is used to produce nitrogen-based fertilisers.

One fertiliser is produced from neutralising ammonia with nitric acid.

What is the name of the compound produced?

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5b4 marks

Ammonium phosphate, (NH4)3PO4, is another fertiliser that can be produced from ammonia.

In the box below, write how many atoms there are of each element in one molecule of ammonium phosphate.

Nitrogen, N  
Hydrogen, H  
Phosphorous, P  
Oxygen, O  

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5c1 mark

Ammonium sulfate is also a fertiliser that can be manufactured by reacting ammonia with an acid.

Which acid would be needed?

  ☐ A Phosphoric acid
  ☐ B Sulfuric acid
  ☐ C Hydrochloric acid
  ☐ D Nitric acid

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5d
Sme Calculator1 mark

NPK fertilisers contain the three essential elements which improve agricultural productivity.

Table 1 shows the percentages of the three elements, nitrogen, phosphorous and potassium which are contained in four different fertilisers, W, X, Y and Z.

Table 1

Percentage (%) of element in fertiliser
Fertiliser Nitrogen  Phosphorus Potassium
W 25 0 0
X 12 0 37
Y 19 22 0
Z 23 18 21

Which fertiliser contains the highest total percentage of all of the essential elements?

  ☐ A Fertiliser W
  ☐ B Fertiliser X
  ☐ C Fertiliser Y
  ☐ D Fertiliser Z

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5e1 mark

When plants do not have sufficient amounts of the three essential elements, they do not grow as well and show visible signs.

  • Plants lacking in nitrogen can have yellow leaves
  • Plants lacking in phosphorus can be slow to grow
  • Plants lacking in potassium can have wilted leaves

Which of the fertilisers in Table 1 would be best to treat land where the plants are growing slowly and have wilted leaves?

Use the information in Table 1.

Tick (✓) one box.

  ☐ A Fertiliser W
  ☐ B Fertiliser X
  ☐ C Fertiliser Y
  ☐ D Fertiliser Z

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1a4 marks

Higher Only

Sulfur trioxide is produced by reacting sulfur dioxide with oxygen.

2SO2 + O2 rightwards harpoon over leftwards harpoon2SO3

i)
This reaction takes place in industry at 1–2 atm pressure and can reach a dynamic equilibrium.

Explain the effect on the rate of attainment of equilibrium, if the process is carried out at a pressure higher than 1–2 atm.

(3)

ii)
What volume of oxygen, in cm3, would react completely with 500 cm3 sulfur dioxide?
(1)
  ☐ A 500 ÷ 2
  ☐ B 500
  ☐ C 500 × 2
  ☐ D 500 × 32 

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1b1 mark

Higher Only

When there are alternative methods of producing a product, the final pathway is chosen by considering atom economy, cost of energy, yield of product and rates of reactions.

State another factor that should also be considered.

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1c6 marks

Higher Only

The reaction between nitrogen and hydrogen is exothermic.

N2 + 3H2 rightwards harpoon over leftwards harpoon 2NH3

If nitrogen and hydrogen were reacted at 150 atm pressure and 300°C, without a catalyst, some ammonia would be formed.

In the Haber process a pressure of 150 atm and a temperature of 450°C are used, in the presence of an iron catalyst.

Explain why the conditions used in the Haber process are better than the first set of conditions for the manufacture of ammonia.

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2a2 marks

Nitric acid can be titrated with a solution of ammonia.


i)
State the type of reaction occurring when nitric acid reacts with ammonia.


(1)

ii)
What salt is formed in this reaction?                                                                                 
(1)
  ☐ A ammonia nitric
  ☐ B ammonia nitrate
  ☐ C ammonium nitric
  ☐ D ammonium nitrate

 

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2b
Sme Calculator4 marks

Higher Only

In one stage of the production of nitric acid, nitrogen oxide, NO, is reacted with oxygen to make nitrogen dioxide, NO2. 

2NO + O2 → 2NO2
 

Calculate the minimum volume of air, measured at room temperature and pressure, required to react with 1000 g nitrogen oxide to form nitrogen dioxide.

 

Assume that the air contains 20% oxygen by volume.

(relative atomic masses: N = 14, O = 16

1 mol of gas occupies 24 dm3 at room temperature and pressure)

 
volume of air = .............................. dm3

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2c6 marks

Higher Only

In another stage in the production of nitric acid, ammonia is reacted with oxygen to form nitrogen oxide and water.

 
4NH3 (g) + 5O2 (g) rightwards harpoon over leftwards harpoon 4NO (g) + 6H2O (g)
 

Heat energy is given out when ammonia reacts with oxygen.

 

The conditions chosen for the reaction are

  • excess air, rather than just the right amount
  • a pressure of 10 atm, rather than atmospheric pressure
  • a temperature of 900 °C, rather than room temperature.


Explain the effect of the conditions chosen on the equilibrium yield of nitrogen oxide and on the rate of attainment of equilibrium.

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3a6 marks

Higher Tier Only 

Ammonia is manufactured by the Haber process.

The equation for the reaction is

N2 (g) + 3H2 (g) rightwards harpoon over leftwards harpoon with blank on top 2NH3 (g)

The reaction is reversible and can reach equilibrium.

i)
An iron catalyst can be used in the reaction.

Which row of the table shows how adding the iron catalyst affects the rate of attainment of equilibrium and the equilibrium yield of ammonia?
(1)
      rate of attainment of
equilibrium		 equilibrium yield of
ammonia
  ☐ A increases increases
  ☐ B decreases  does not change
  ☐ C decreases  increases
  ☐ D increases  does not change

ii)
Which of the following statements is correct when the reaction reaches equilibrium?
(1)
  ☐ A the reverse reaction starts to take place
  ☐ B the amounts of nitrogen, hydrogen and ammonia are equal 
  ☐ C the amounts of nitrogen, hydrogen and ammonia become constant 
  ☐ D the reaction stops 

iii)
The reaction is carried out at a pressure of 200 atmospheres.

Explain what effect a pressure higher than 200 atmospheres would have on the rate of attainment of equilibrium and on the equilibrium yield of ammonia.
(4)

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3b5 marks

Ammonium sulfate and ammonium nitrate are used as fertilisers as they both contain nitrogen, which will increase the yield of crops.

i)
Suggest one other reason for using solid ammonium sulfate and solid ammonium nitrate as nitrogenous fertilisers.
(1)
ii)
Ammonium nitrate can be made by the reaction of ammonia with nitric acid.
Write the balanced equation for this reaction.
(2)
iii)
Describe one similarity and one difference between the industrial production of ammonium sulfate and the laboratory preparation of ammonium sulfate.
(2)
similarity...................................................

difference.................................................

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4a2 marks

When hydrogen and nitrogen react to form ammonia, the reaction can reach a dynamic equilibrium.

N2  +   3H2   rightwards harpoon over leftwards harpoon   2NH3

Explain what is meant by a dynamic equilibrium.

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4b3 marks

Higher Only

The pressure used in the Haber process is approximately 200 atmospheres.

Explain how the use of a higher pressure would affect the equilibrium yield of ammonia.

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4c3 marks

Higher Only

The reaction to form ammonia is exothermic. The temperature used is approximately 450 °C.

Explain how the use of a lower temperature would affect the equilibrium yield of ammonia.

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4d3 marks

Higher Only

Undertaking the Haber process at 450 oC still means the reaction is very slow. 

Explain how this problem can be overcome in industry.

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5a3 marks

Ammonia can be used to produce salts used as fertilisers. 

Two of these salts include ammonium sulfate and ammonium nitrate. 

Write a balanced symbol equation for the production of ammonium sulfate from ammonia and sulfuric acid. 

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5b4 marks

Compare the industrial production of ammonium sulfate with laboratory production. 

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5c4 marks

Describe a method that could be used to prepare ammonium sulfate in the laboratory. 

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5d4 marks

Higher Only

Ammonia is reacted with excess nitric acid, HNO3, to make ammonium nitrate, NH4NO3.

NH3 + HNO3 → NH4NO3

Calculate the mass of ammonium nitrate produced by the complete reaction of 46 kg of ammonia.

Give your answer in grams to three significant figures.

(Relative atomic masses H = 1.0, N = 14, O = 16)

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11 mark

What essential plant nutrients do fertilisers supply?

  ☐ A phosphorus, calcium, nitrogen
  ☐ B iron, nitrogen, magnesium
  ☐ C nitrogen, potassium, phosphorus
  ☐ D potassium, calcium, nitrogen

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21 mark

Ammonia and sulfuric acid can react in the laboratory to make ammonium sulfate fertiliser.

What is the formula of the product?

  ☐ A NH3SO4
  ☐ B NH4SO4
  ☐ C (NH4)2SO4
  ☐ D (NH3)2SO4

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31 mark

Higher Tier Only

Ammonia is manufactured by the Haber process.

The reaction that occurs is:

N2 (g) + 3H2 (g) rightwards harpoon over leftwards harpoon 2NH3 (g)

A temperature of 450 oC is used instead of room temperature, and an iron catalyst can also be added.

Which row of the table shows how the temperature and the catalyst affect the rate of attainment of equilibrium?

      Effect of increasing temperature to 450 oC on the rate of attainment of equilibrium Effect of adding an iron catalyst on the rate of attainment of equilibrium
  ☐ A decreases does not change
  ☐ B decreases increases
  ☐ C increases does not change
  ☐ D increases increases

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41 mark

Higher Tier Only 

Ammonia is manufactured by the Haber process.

The reaction that occurs is:

N2 (g) + 3H2 (g) → 2NH3 (g)

The reaction is carried out at a pressure of 200 atmospheres. A higher pressure would give a greater equilibrium yield of ammonia.

Which of these statements is not a correct reason for the choice of pressure in the Haber process?

  ☐ A A higher pressure requires more expensive safety equipment
  ☐ B 200 atmospheres still gives an acceptable yield in an acceptable time
  ☐ C A higher pressure would make the reaction occur too quickly
  ☐ D A higher pressure would increase the chance of explosions occurring

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5a2 marks

Figure 1 shows the dot and cross diagram for a molecule of ammonia.

fig-1

Figure 1

i)
What do the dots and crosses represent in the diagram?
(1)
  ☐ A electrons
  ☐ B neutrons 
  ☐ C protons 
  ☐ D nuclei

ii)
Give the formula for the molecule of ammonia.

(1)

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5b3 marks
i)
Ammonia can be manufactured by the Haber process.

The word equation for the reaction is

nitrogen + hydrogen rightwards harpoon over leftwards harpoon ammonia

State the meaning of the rightwards harpoon over leftwards harpoon symbol.

(1)

ii)
In the Haber process, the percentage yield of ammonia at equilibrium changes with temperature.

Figure 2 shows how the percentage yield of ammonia at equilibrium changes with temperature.
fig-2-q1bii-1cho-1f-paper-1-june-2018
Figure 2

State what happens to the percentage yield of ammonia at equilibrium as the temperature increases.

(1)

iii)
Use the graph to find the percentage yield of ammonia at equilibrium at 450 °C.
(1)
percentage yield of ammonia at equilibrium = ..............................................

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5c1 mark

Ammonia reacts with nitric acid to form ammonium nitrate.

i)
Complete the word equation for this reaction.
(1)

................. + .................. → ........................

ii)
An ammonium ion has the formula NH4+.

A nitrate ion has the formula NO3-.

Which of the following is the formula for ammonium nitrate?

(1)

  ☐ A (NH)4NO3
  ☐ B (NH4NO)3 
  ☐ C NH4NO3 
  ☐ D (NHNO)12 

iii)
Explain why farmers spread ammonium nitrate on their fields.
(2)

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61 mark

Ammonium sulfate can be made by a laboratory preparation or an industrial process.

Which of the following statements is not a correct difference between the laboratory preparation and the industrial process?

  ☐ A The industrial process is on a much larger scale than the laboratory preparation
  ☐ B The industrial process is a batch process
  ☐ C Ammonia is used as a gas in the industrial process and as a solution in the laboratory preparation
  ☐ D The laboratory preparation involves titration and crystallisation steps

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7a3 marks

Fertilisers contain compounds that promote plant growth.

i)
State the name of an element in these compounds that promotes plant growth.  
(1)
ii)
Potassium nitrate is present in some fertilisers.

Potassium nitrate is formed by the reaction of potassium hydroxide solution with nitric acid.

Complete the balanced equation for this reaction. 
(2)
KOH + HNO3 → .............................. + ..............................

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7b3 marks

In the Haber process, hydrogen and nitrogen react to form ammonia. 

hydrogen + nitrogen rightwards harpoon over leftwards harpoon ammonia

i)
The rightwards harpoon over leftwards harpoon symbol in the word equation shows that the reaction goes forwards and backwards at the same time.

Give the name of this type of reaction.
(1)
ii)
State the formula of a molecule of ammonia. 
(1)

iii)
Figure 7 shows a graph of world ammonia production, in millions of tonnes, from 1945 to 2015. 
fig-7-q7biii-1cho-1f-paper-1-june-2019
Figure 7

State the overall trend in world ammonia production from 1945 to 2015.

(1)

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7c1 mark

Hydrogen can also be used in a hydrogen-oxygen fuel cell.

Give the name of the product formed in this fuel cell.  

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7d6 marks

Ammonia solution and dilute sulfuric acid are used to prepare pure, dry ammonium sulfate crystals.

In an experiment a titration is carried out to determine the volumes of ammonia solution and dilute sulfuric acid that react together.

Then an ammonium sulfate solution is prepared from which the pure, dry crystals are obtained.

Describe in detail, using suitable apparatus, how this experiment should be carried out. 

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81 mark

What numbers are required to balance the equations showing the reaction between ammonia and sulfuric acid?

___ NH3 (aq) + ___ H2SO4 (aq)  rightwards arrow ___ (NH4)2SO4  (aq)

  ☐ A 2, 1, 2
  ☐ B 2, 1, 1
  ☐ C 1, 2, 1
  ☐ D 2, 2, 1

                  

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9a2 marks

Ammonia is made by reacting nitrogen with hydrogen.

The nitrogen and hydrogen are obtained from raw materials.

Draw one straight line from each gas to the raw material it is obtained from.

fig-q5a-1cho-1f-paper-1-nov-2021

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9b2 marks

When nitrogen and hydrogen are reacted together, the reaction can reach a dynamic equilibrium.

Use words from the box to complete the sentences about dynamic equilibrium.

     backward    different    equal    faster   reversible

In a dynamic equilibrium two reactions occur at the same time.

These are the forward reaction and the ............................... reaction.

The rates of the two reactions are ...............................

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9c2 marks

The reaction between nitrogen and hydrogen happens at a pressure of 200 atmospheres.

Another unit of pressure is Pascals, Pa (1 atmosphere = 101325 Pa).
   
Calculate the value of 200 atmospheres in Pascals.

pressure = ............................................................. Pa

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9d3 marks

Figure 5 shows molecules of nitrogen, hydrogen and ammonia before the reaction and at equilibrium.

fig-5-q5d-1cho-1f-paper-1-nov-2021

Figure 5

i)
Complete the table showing

   • the number of hydrogen molecules before reaction
   • the number of hydrogen molecules at equilibrium
   • the change in the number of hydrogen molecules.

  number of molecules before reaction number of molecules at equilibrium change in number of molecules
nitrogen 4 2 -2
hydrogen .................. ................  
ammonia 0 4 +4

(1)

ii)
Complete the equation for this reaction.

(2)

......................... + ............................... rightwards harpoon over leftwards harpoon for blank of 2NH3

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101 mark

The Haber process is used to make ammonia, and ammonia is used to make nitric acid.

Ammonia and nitric acid can be reacted to make a salt that can be used as a fertiliser.

What is the formula of the salt made from this reaction?

  ☐ A NH4NO3
  ☐ B NH3NO4
  ☐ C NH3(NO3)2
  ☐ D NH4(NO3)2

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