Homogeneous and heterogeneous catalysts — Paper 1 · A Level Chemistry 9701

33 A reversible reaction is catalysed. Which statements about the effects of the catalyst on this system are correct? 1 The catalyst alters the mechanism of the reaction. 2 The catalyst reduces the energy of activation (the energy barrier) for both the forward and the backward reaction. 3 The catalyst alters the composition of the equilibrium mixture.

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2006

21 Tetramethyl-lead(IV), (CH3)4Pb, increases the rate of the reaction of methane with chlorine. CH4(g) + Cl2(g) → CH3Cl(g) + HCl(g) Why can tetramethyl-lead(IV) behave in this way? A It is a source of methyl radicals. B It releases CH3 + (g) . C It reacts with chloromethane and prevents equilibrium being established. D Metal ions catalyse the reaction.

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2007

18 The diagram represents the Haber process for the manufacture of ammonia from nitrogen and hydrogen. heat exchanger N2 + H2 catalytic converter condenser NH3 What is the purpose of the heat exchanger? A to cool the incoming gas mixture to avoid overheating the catalyst B to cool the reaction products and separate the NH3 from unused N2 and H2 C to warm the incoming gas mixture and shift the equilibrium to give more NH3 D to warm the incoming gas mixture and speed up the reaction

1 marks

Answer: D

This question in 9701/11 May/June 2008

33 Which statements about the properties of a catalyst are correct? 1 A catalyst increases the average kinetic energy of the reacting particles. 2 A catalyst increases the rate of the reverse reaction. 3 A catalyst has no effect on the enthalpy change of the reaction.

1 marks

Answer: C

This question in 9701/11 May/June 2008

12 Crotonaldehyde, CH3CH=CHCHO, can be obtained by oxidising butadiene, CH2=CHCH=CH2, using air or oxygen. One method is to pass a mixture of butadiene and oxygen through a hot aqueous solution of palladium(II) ions, Pd2+(aq), which catalyse the reaction. Which statement is not correct about the action of the Pd2+(aq) ions? A Changing the concentration of the Pd2+(aq) will have an effect on the rate of the reaction. B Pd2+(aq) increases the energy of the reacting molecules. C Pd2+(aq) lowers the activation energy for the reaction. D When Pd2+(aq) is used, the reaction proceeds by a different route.

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2008

36 Which statements about the Haber process for the industrial production of ammonia are correct? 1 The equilibrium constant Kp increases with pressure. 2 As the temperature increases, the equilibrium constant for the forward reaction becomes smaller. 3 The process is usually carried out at between 450 °C and 550 °C at a pressure of at least 150 atm.

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2008

10 The diagram shows the Maxwell-Boltzmann energy distribution curve for molecules of a mixture of two gases at a given temperature. For a reaction to occur the molecules must collide together with sufficient energy. number of molecules 00 Ea2 Ea1 energy Ea is the activation energy for the reaction between the gases. Of the two values shown, one is for a catalysed reaction, the other for an uncatalysed one. Which pair of statements is correct when a catalyst is used? A Ea1 catalysed reaction Ea2 uncatalysed reaction fewer effective collisions more effective collisions B Ea1 uncatalysed reaction Ea2 catalysed reaction fewer effective collisions more effective collisions C Ea1 catalysed reaction Ea2 uncatalysed reaction more effective collisions fewer effective collisions D Ea1 uncatalysed reaction Ea2 catalysed reaction more effective collisions fewer effective collisions

1 marks

Answer: B

This question in 9701/11 May/June 2009

32 The diagram represents the Boltzmann distribution of molecular energies at a given temperature. proportion of molecules energy Which of the factors that affect the rate of a reaction can be explained using such a Boltzmann distribution? 1 increasing the concentration of reactants 2 increasing the temperature 3 the addition of a catalyst

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2010

33 The diagram represents the Boltzmann distribution of molecular energies at a given temperature. proportion of molecules energy Which of the factors that affect the rate of a reaction can be explained using such a Boltzmann distribution? 1 increasing the concentration of reactants 2 increasing the temperature 3 the addition of a catalyst

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2010

4 Different Boltzmann distributions are shown in the diagrams. diagram 1 diagram 2 X P Y number of Q number of molecules molecules 00 00 molecular speed molecular speed In diagram 1, one curve P or Q corresponds to a temperature higher than that of the other curve. In diagram 2, one line X or Y corresponds to the activation energy for a catalysed reaction and the other line corresponds to the activation energy of the same reaction when uncatalysed. Which combination gives the correct curve and line? higher presence of temperature catalyst A P X B P Y C Q X D Q Y

1 marks

Answer: C

This question in 9701/11 May/June 2011

7 Different Boltzmann distributions are shown in the diagrams. diagram 1 diagram 2 X P Y number of Q number of molecules molecules 00 00 molecular speed molecular speed In diagram 1, one curve P or Q corresponds to a temperature higher than that of the other curve. In diagram 2, one line X or Y corresponds to the activation energy for a catalysed reaction and the other line corresponds to the activation energy of the same reaction when uncatalysed. Which combination gives the correct curve and line? higher presence of temperature catalyst A P X B P Y C Q X D Q Y

1 marks

Answer: C

This question in 9701/13 May/June 2011

12 Butanedioate ions can be dehydrogenated to form trans-butenedioate ions. The enzyme fumarase speeds up this reaction. Why does fumarase speed up this reaction? A Fumarase is a protein. B Fumarase is effective at body temperature. C Fumarase lowers the activation energy of the dehydrogenation reaction. D The enzyme fumarase is specific for this dehydrogenation reaction.

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2011

1 In the Haber process for the manufacture of ammonia, why is the heterogeneous catalyst iron in a finely divided state? A to increase its surface area B to produce the maximum reduction in the activation energy C to reduce its loss during the reaction D to reduce its surface area

1 marks

This question in 9701/12 Oct/Nov 2011

2 Ammonia is manufactured by the Haber Process, in an exothermic reaction. Assuming that the amount of catalyst remains constant, which change will not bring about an increase in the rate of the forward reaction? A decreasing the size of the catalyst pieces B increasing the pressure C increasing the temperature D removing the ammonia as it is formed

1 marks

Answer: D

This question in 9701/11 May/June 2012

8 The gaseous compound Z decomposes on heating. In the diagram below, Boltzmann distributions for Z at two different temperatures P and Q are shown. The lines X and Y indicate activation energies for the decomposition of Z with and without a catalyst. X Y P number of molecules Q 0 0 energy Which curve and which line describe the decomposition of Z at a higher temperature and with a catalyst present? higher temperature catalyst present A P X B P Y C Q X D Q Y

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2012

36 Sulfur dioxide is an atmospheric pollutant that causes acid rain. One of the reactions in this process is the oxidation of sulfur dioxide to sulfur trioxide. This oxidation takes place by a two stage reaction involving oxygen and nitrogen monoxide, NO. NO + 2 1 O2 → NO2 NO2 + SO2 → SO3 + NO Which statements are correct? 1 Nitrogen monoxide is acting as a catalyst for the oxidation. 2 Nitrogen atoms are oxidised in the second stage. 3 Oxygen atoms are first reduced and are then oxidised.

1 marks

Answer: D

This question in 9701/12 May/June 2013

5 Crotonaldehyde, CH3CH=CHCHO, can be obtained by oxidising butadiene, CH2=CHCH=CH2, using air or oxygen. One method is to pass a mixture of butadiene and oxygen through a hot aqueous solution of palladium(II) ions, Pd2+(aq), which catalyse the reaction. Which statement is not correct about the action of the Pd2+(aq) ions? A Changing the concentration of the Pd2+(aq) will have an effect on the rate of the reaction. B Pd2+(aq) increases the energy of the reacting molecules. C Pd2+(aq) lowers the activation energy for the reaction. D Pd2+(aq) provides a different route for the reaction.

1 marks

Answer: B

This question in 9701/13 May/June 2013

11 Boltzmann distributions are shown in the diagrams. diagram 1 diagram 2 X Y P number of Q number of molecules molecules 0 0 0 0 molecular energy molecular energy In diagram 1, one curve, P or Q, corresponds to a temperature higher than that of the other curve. In diagram 2, one line, X or Y, corresponds to the activation energy in the presence of a catalyst and the other line corresponds to the activation energy of the same reaction in the absence of a catalyst. Which combination gives the correct curve and line? higher presence of temperature catalyst A P X B P Y C Q X D Q Y

1 marks

Answer: C

This question in 9701/11 May/June 2014

5 In the diagram, curve X was obtained by observing the decomposition of 100 cm3 of 1.0 mol dm–3 hydrogen peroxide, catalysed by manganese(IV) oxide. Y X volume of oxygen formed 0 0 time Which alteration to the original experimental conditions would produce curve Y? A adding more manganese(IV) oxide B adding some 0.1 mol dm–3 hydrogen peroxide C adding water D raising the temperature

1 marks

Answer: B

This question in 9701/12 May/June 2014

32 The reaction E + F G + H is catalysed by platinum. Which statements about the properties of the catalyst are correct? 1 The catalyst has no effect on the enthalpy change of the reaction. 2 The catalyst increases the rate of the reverse reaction. 3 The catalyst increases the average kinetic energy of the reacting particles.

1 marks

Answer: B

This question in 9701/12 May/June 2014

36 A car has a catalytic converter fitted to its exhaust. On analysis its exhaust gases are shown to contain small quantities of nitrogen oxides. Which modifications would result in lower exhaust concentrations of nitrogen oxides? 1 an increase in the surface area of the catalyst in the converter 2 an increase in the rate of flow of the exhaust gases through the converter 3 a much higher temperature of combustion in the engine

1 marks

Answer: D

This question in 9701/12 May/June 2014

34 The stoichiometry of a catalysed reaction is shown by the equation below. P (g) + Q (g) R (g) + S (l) Two experiments were carried out in which the rate of production of R was measured. The results are shown in the diagram below. experiment 1 amount experiment 2 of R 00 time Which changes in the conditions might explain the results shown? 1 A lower pressure was used in experiment 2. 2 A different catalyst was used in experiment 2. 3 Product S was continuously removed from the reaction vessel in experiment 2.

1 marks

Answer: B

This question in 9701/13 May/June 2014

33 A reversible reaction is catalysed. Which statements about the effects of the catalyst on this system are correct? 1 The catalyst alters the mechanism of the reaction. 2 The catalyst reduces the activation energy for both the forward and the backward reaction. 3 The catalyst alters the composition of the equilibrium mixture.

1 marks

Answer: B

This question in 9701/11 Oct/Nov 2014

33 A reversible reaction is catalysed. Which statements about the effects of the catalyst on this system are correct? 1 The catalyst alters the mechanism of the reaction. 2 The catalyst reduces the activation energy for both the forward and the backward reaction. 3 The catalyst alters the composition of the equilibrium mixture.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2014

1 The diagram below represents, for a given temperature, the Boltzmann distribution of the kinetic energy of the molecules in a mixture of two gases that react slowly together. The activation energy for the reaction, Ea, is marked. When the reaction is catalysed, the rate of reaction increases a little. What will be the position of Ea for the catalysed reaction? number of molecules kinetic Ea energy A B C D

1 marks

Answer: B

This question in 9701/13 Oct/Nov 2014

1 The diagram shows a Boltzmann distribution of molecular energies for a gaseous mixture. The distribution has a peak, labelled P on the diagram. P activation number of energy molecules 00 molecular energy What happens when an effective catalyst is added to the mixture? A The height of the peak decreases and the activation energy moves to the right. B The height of the peak decreases and the activation energy moves to the left. C The height of the peak remains the same and the activation energy moves to the right. D The height of the peak remains the same and the activation energy moves to the left.

1 marks

Answer: D

This question in 9701/11 May/June 2015

11 Catalysts are an important feature of many industrial processes and biochemical reactions. Which row correctly describes the effect of a catalyst on a reversible chemical reaction? position of equilibrium effect on value of ∆H A moved to right decreased B unaffected decreased C unaffected increased D unaffected unaffected

1 marks

Answer: D

This question in 9701/13 May/June 2016

11 An autocatalytic reaction is a reaction in which one of the products catalyses the reaction. Which curve would be obtained if the rate of an autocatalytic reaction is plotted against time? A B C D rate rate rate rate 0 0 0 0 0 0 0 0 time time time time

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2016

11 An autocatalytic reaction is a reaction in which one of the products catalyses the reaction. Which curve would be obtained if the rate of an autocatalytic reaction is plotted against time? A B C D rate rate rate rate 0 0 0 0 0 0 0 0 time time time time

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2016

34 In the manufacture of sulfuric acid, the following exothermic reaction occurs. 2SO2(g) + O2(g) 2SO3(g) Which changes will move the position of the equilibrium to the right? 1 increasing the pressure 2 increasing the temperature 3 using twice as much catalyst

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2016

11 The Boltzmann distribution for the hydrogenation of an alkene at a particular temperature in the absence of a catalyst is shown. proportion of molecules Ea with energy E 00 molecular energy E Which row correctly describes the effects of adding nickel to the reaction vessel? the shape of the activation energy, Ea Boltzmann distribution A changes decreases B changes increases C does not change decreases D does not change increases

1 marks

Answer: C

This question in 9701/12 May/June 2017

34 The rate of chemical reactions can be increased by the addition of a suitable catalyst. For which reactions can a heterogeneous catalyst be used? 1 N2 + 3H2 2NH3 2 2SO2 + O2 2SO3 3 2NO + 2CO N2 + 2CO2

1 marks

Answer: A

This question in 9701/12 May/June 2017

10 The diagram shows the distribution of molecular energies in a sample of gas at a temperature T1. The activation energy for an uncatalysed reaction of this gas, Ea(uncat), is shown. T1 proportion Ea(uncat) of molecules with a given energy 0 0 molecular energy E Which diagram correctly shows the new distribution and new activation energy, Ea(cat), when the temperature is increased to T2, and a catalyst is used that increases the rate of the reaction? A B T1 T1 Ea(cat) proportion Ea(uncat) proportion Ea(uncat) T2 T2 of molecules Ea(cat) of molecules with a given with a given energy energy 0 0 0 molecular energy E 0 molecular energy E C D T1 Ea(cat) T1 proportion Ea(uncat) proportion Ea(uncat) of molecules of molecules Ea(cat) with a given with a given energy T2 energy T2 0 0 0 molecular energy E 0 molecular energy E

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2017

10 The diagram shows the distribution of molecular energies in a sample of gas at a temperature T1. The activation energy for an uncatalysed reaction of this gas, Ea(uncat), is shown. T1 proportion Ea(uncat) of molecules with a given energy 0 0 molecular energy E Which diagram correctly shows the new distribution and new activation energy, Ea(cat), when the temperature is increased to T2, and a catalyst is used that increases the rate of the reaction? A B T1 T1 Ea(cat) proportion Ea(uncat) proportion Ea(uncat) T2 T2 of molecules Ea(cat) of molecules with a given with a given energy energy 0 0 0 molecular energy E 0 molecular energy E C D T1 Ea(cat) T1 proportion Ea(uncat) proportion Ea(uncat) of molecules of molecules Ea(cat) with a given with a given energy T2 energy T2 0 0 0 molecular energy E 0 molecular energy E

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2017

4 The diagram shows the Boltzmann distribution of energies in a gas. The gas can take part in a reaction with an activation energy, Ea. The gas is maintained at a constant temperature. P proportion of molecules with a given energy 0 0 Ea molecular energy Which statement is correct? A If a catalyst is added, peak P will be lower and Ea will move to the left. B If a catalyst is added, peak P will be lower and Ea will move to the right. C If a catalyst is added, peak P will be the same and Ea will move to the left. D If a catalyst is added, peak P will be the same and Ea will move to the right.

1 marks

Answer: C

This question in 9701/11 May/June 2018

11 Two reactions are shown. reaction 1 N2(g) + 3H2(g) 2NH3(g) reaction 2 2O3(g) 3O2(g) In reaction 1, a finely powdered iron catalyst is used. In reaction 2, a vaporised tetrachloromethane catalyst in ultraviolet light is used. Which statement about the catalysts used is correct? A Both reaction 1 and reaction 2 use a heterogeneous catalyst. B Both reaction 1 and reaction 2 use a homogeneous catalyst. C Reaction 1 uses a heterogeneous catalyst and reaction 2 uses a homogeneous catalyst. D Reaction 1 uses a homogeneous catalyst and reaction 2 uses a heterogeneous catalyst.

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2018

10 In a chemical system the particles involved have a range of energies. This can be shown on a graph called the Boltzmann distribution. Which statement correctly explains the effect of a catalyst on the particles in a chemical system? A A catalyst enables particles with a lower energy to collide successfully. B A catalyst increases the number of particles with higher energies. C A catalyst increases the number of particles with the most probable energy value. D A catalyst increases the value of the most probable particle energy.

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2018

11 Nitrogen and hydrogen can react together to form ammonia. The formation of ammonia is exothermic. The rate and yield of the reaction can be altered by changing the conditions under which the reaction is carried out. Which row shows the effects of adding iron to the mixture and increasing the temperature? adding iron increasing the temperature A has no effect on the equilibrium yield reduces the equilibrium yield B increases the equilibrium yield increases the equilibrium yield C increases the equilibrium yield increases the rate D increases the rate has no effect on the equilibrium yield

1 marks

Answer: A

This question in 9701/12 Oct/Nov 2018

34 Some polluting gases are removed from car exhaust fumes using a catalytic converter. Platinum or palladium can be used as the catalyst. The reactions are faster when platinum is the catalyst than they are when palladium is the catalyst. Which statements are correct? 1 Platinum acts as a heterogeneous catalyst in these reactions. 2 The palladium-catalysed reactions have higher activation energies than the platinum-catalysed reactions. 3 The platinum-catalysed reactions are more exothermic than the palladium-catalysed reactions.

1 marks

Answer: B

This question in 9701/12 Feb/March 2019

38 Chlorine atoms in the upper atmosphere cause the breakdown of ozone. Cl + O3 → O2 + Cl O Cl O + O → Cl + O2 Which statements about these chlorine atoms are correct? 1 The chlorine atoms act as catalysts. 2 The chlorine atoms are free radicals. 3 The chlorine atoms are formed by heterolytic fission of a covalent bond in chlorofluorocarbons.

1 marks

Answer: B

This question in 9701/12 Feb/March 2019

34 Vanadium and pepsin can both act as catalysts. Vanadium is a metal. Pepsin is an enzyme. Which statements are correct for both vanadium and pepsin? 1 They will speed up any chemical reaction. 2 They can lower the activation energy for a reaction. 3 They are not used up when they act as catalysts.

1 marks

Answer: C

This question in 9701/11 May/June 2019

1 The Boltzmann distribution of molecular energies in a sample of aqueous hydrogen peroxide at room temperature is shown. molecules proportion of with sufficient molecules with energy to react energy, E 0 0 molecular energy, E Which diagram shows the Boltzmann distribution of molecular energies of aqueous hydrogen peroxide maintained at room temperature when a catalyst, manganese(IV) oxide, is added? A B molecules molecules with sufficient proportion of proportion of with sufficient energy to react molecules with molecules with energy to react energy, E energy, E 0 0 0 molecular energy, E 0 molecular energy, E C D molecules molecules with sufficient with sufficient proportion of energy to react proportion of energy to react molecules with molecules with energy, E energy, E 0 0 0 molecular energy, E 0 molecular energy, E

1 marks

Answer: B

This question in 9701/12 May/June 2019

34 The manufacture of ammonia from nitrogen and hydrogen is an important industrial process. Which of the following would leave the equilibrium constant, Kp, for the formation of ammonia unchanged? 1 addition of an iron catalyst 2 addition of ammonia 3 an increase in pressure

1 marks

Answer: A

This question in 9701/12 May/June 2019

1 The diagram shows a Boltzmann distribution of the energies of gaseous molecules and the activation energies, Ea, of a reaction with and without a catalyst. proportion of molecules with energy, E 00 Ea1 Ea2 molecular energy, E Which statement about this distribution curve is correct? A If the temperature of the gas is increased, the maximum of the curve becomes higher. B If the temperature of the gas is increased, the maximum of the curve moves to the left. C The fraction of molecules that react in the presence of a catalyst is shown by . D The fraction of molecules that react in the absence of a catalyst is shown by .

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2019

1 The diagram shows the Boltzmann distribution of energies in a gas. The gas undergoes a reaction with an activation energy, Ea. The peak of the distribution is labelled P. P proportion of molecules with energy E 0 0 Ea molecular energy, E If the same reaction is carried out in the presence of a catalyst, which statement is correct? A The peak P is at a lower height and the position of Ea moves to the left. B The peak P is at a lower height and the position of Ea moves to the right. C The peak P remains at the same height and the position of Ea moves to the left. D The peak P remains at the same height and the position of Ea moves to the right.

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2019

34 Hydrochloric acid reacts with zinc. 2HCl (aq) + Zn(s) → ZnCl 2(aq) + H2(g) What will increase the rate of this reaction but will not change the Boltzmann distribution of molecular energies? 1 addition of a suitable catalyst 2 an increase in concentration of hydrochloric acid 3 an increase in temperature of hydrochloric acid

1 marks

Answer: B

This question in 9701/12 Feb/March 2020

3 The catalysed formation of ammonia by the Haber process can be represented by the equation shown. N2(g) + 3H2(g) 2NH3(g) ∆H = –92 kJ mol–1 Which change in conditions will increase both the rate of formation and the equilibrium yield of ammonia? A decrease in the temperature B increase in the temperature C increase in the pressure D increase in the surface area of the catalyst

1 marks

Answer: C

This question in 9701/12 May/June 2020

34 The Haber process is used in industry to form ammonia from hydrogen and nitrogen. 3H2 + N2 2NH3 Which statements about the activation energy for this process are correct? 1 The activation energy for the forward reaction is the same as the activation energy for the reverse reaction. 2 The activation energy for the reverse reaction is decreased by the addition of iron. 3 The activation energy is the minimum energy that colliding particles must possess in order to react.

1 marks

Answer: C

This question in 9701/13 May/June 2020

11 An autocatalytic reaction is a reaction in which one of the products catalyses the reaction. Which curve would be obtained if the rate of an autocatalytic reaction is plotted against time? A B C D rate rate rate rate 00 00 00 00 time time time time

1 marks

Answer: C

This question in 9701/11 Oct/Nov 2020

11 An autocatalytic reaction is a reaction in which one of the products catalyses the reaction. Which curve would be obtained if the rate of an autocatalytic reaction is plotted against time? A B C D rate rate rate rate 00 00 00 00 time time time time

1 marks

Answer: C

This question in 9701/13 Oct/Nov 2020

11 The Boltzmann distribution curve for a gaseous mixture of ethene and hydrogen is shown. Nickel is an effective catalyst for the reaction that occurs. number of particles with energy, E Ea (catalysed) Ea 0 0 energy, E How does the diagram appear if the same reaction mixture is at a higher temperature? A The curve is unchanged. B The values of both Ea (catalysed) and Ea decrease. C The values of both Ea (catalysed) and Ea increase. D The values of both Ea (catalysed) and Ea remain the same.

1 marks

Answer: D

This question in 9701/12 Feb/March 2021

11 Which statement about catalysts is correct? A They change the reaction pathway by increasing the activation energy. B They increase the rate of reaction by lowering the enthalpy change of the reaction. C They increase the number of particles that have sufficient energy to react. D Heterogeneous catalysts are in the same state as the reactant.

1 marks

Answer: C

This question in 9701/11 May/June 2021

7 The reaction pathway diagram for the catalysed reaction and the uncatalysed reaction between N2 and H2 is shown. N2(g) + 3H2(g) 2NH3(g) Which letter represents the activation energy for the first step in the decomposition of NH3 in the presence of a catalyst? A C B energy N2(g) + 3H2(g) D 2NH3(g) reaction pathway

1 marks

Answer: D

This question in 9701/12 May/June 2021

32 Iron reacts with steam to produce hydrogen and an oxide of iron. 3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g) A system containing all four substances is at equilibrium. Which changes will decrease the mass of Fe present at equilibrium? 1 addition of steam at constant pressure 2 increase in overall pressure 3 addition of an effective catalyst

1 marks

Answer: D

This question in 9701/11 Oct/Nov 2021

11 NO and NO2 are both present in the lower atmosphere as pollutants. The reaction sequence shows the production of ozone from oxygen in the lower atmosphere. This sequence repeats many times. NO2(g)  NO(g) + O(g) NO(g) + 1 2 O2(g)  NO2(g) O2(g) + O(g)  O3(g) Which statement about this reaction sequence is correct? A NO is acting as a catalyst, but NO2 is not acting as a catalyst. B NO2 is acting as a catalyst, but NO is not acting as a catalyst. C Neither NO nor NO2 are acting as catalysts. D Both NO and NO2 are acting as catalysts.

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2021

11 The diagram shows the Boltzmann distribution of energies for a reactant gas. For a particular reaction, the activation energy is X. number of particles with energy, E 0 0 X energy, E Which change to the diagram occurs if an effective catalyst is added at the same temperature? A More particles will possess higher values of E. B The peak will move to the left. C The peak will move to the right. D The value of the activation energy decreases.

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2021

32 Iron reacts with steam to produce hydrogen and an oxide of iron. 3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g) A system containing all four substances is at equilibrium. Which changes will decrease the mass of Fe present at equilibrium? 1 addition of steam at constant pressure 2 increase in overall pressure 3 addition of an effective catalyst

1 marks

Answer: D

This question in 9701/13 Oct/Nov 2021

7 Hydrogen peroxide decomposes slowly at 20 C to form water and oxygen. 2H2O2 2H2O + O2 equilibrium constant = Kc The reaction is faster when a catalyst is present. Which statement is correct? A The catalyst alters the Boltzmann distribution so that the reactant molecules have more energy. B The catalyst has no effect on the value of Kc. C The catalyst increases the value of Kc. D The catalyst provides a different reaction mechanism with a higher activation energy.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2022

11 The Haber process is carried out with a nitrogen partial pressure of 50 kPa, a hydrogen partial pressure of 150 kPa, a temperature of 400 C and an iron catalyst. N2(g) + 3H2(g) 2NH3(g) If all other conditions are kept the same, which change will result in a raised activation energy? A Both the nitrogen and hydrogen partial pressures are changed to 100 kPa. B The iron is removed. C The nitrogen partial pressure is increased to 150 kPa. D The temperature is increased to 500 C.

1 marks

Answer: B

This question in 9701/12 Oct/Nov 2022

16 The decomposition of hydrogen peroxide in the presence of MnO, produces water and oxygen gas. 2H,0,(aq) — 2H,O(!) + O,(g) The volume of gas collected when 0.2g of MnO, is added to two different hydrogen peroxide solutions at 20 °C is shown on the graph as curves X and Y. < x volume of gas 0) time Which row shows the conditions that will result in curves X and Y? curve X curve Y concentration concentration volume of of H.O form of volume of of H.O form of H,0,/cm* an MnO, | H,0,/cm* 22, MnO, /moldm /moldm A 50 0.1 lumps 50 0.2 powder B 25 0.2 powder 25 0.1 lumps Cc 50 0.1 lumps 20 0.2 powder D 20 0.2 powder 40 0.1 lumps

1 marks

Answer: C

This question in 9701/12 Oct/Nov 2023

15 The Boltzmann distribution for the hydrogenation of an alkene at a particular temperature in the absence of a catalyst is shown. proportion of molecules Ea with energy E 0 0 molecular energy E Which row correctly describes the effects of adding a nickel catalyst to the reaction vessel? the shape of the activation energy, Ea Boltzmann distribution A changes decreases B changes increases C does not change decreases D does not change increases

1 marks

Answer: C

This question in 9701/11 May/June 2024

15 Gas Q decomposes slowly at room temperature. Q(g)  X(g) + Z(g) The Boltzmann distribution curve for gas Q at room temperature is shown. number of particles 0 0 Ea energy Which change occurs when a catalyst is added to gas Q? A The peak of the curve moves to the right on the diagram. B The number of particles with enough energy to decompose increases. C The kinetic energy of the unreacted particles increases. D The value of Ea decreases, moving the vertical dotted line to the right on the diagram.

1 marks

Answer: B

This question in 9701/12 May/June 2024

16 The Boltzmann distribution for a mixture of gases capable of reaction is shown. The two curves represent the mixture of gases at 25 C and at 35 C. The activation energies for the catalysed and uncatalysed reactions are shown. Ea catalysed number of particles w Ea uncatalysed x y 0 0 z energy Which row is correct? number of particles with number of particles with enough energy to react at 25 C enough energy to react at 35 C in the catalysed reaction in the uncatalysed reaction A w + x + y + z z B w + x + y + z x + z C y + z z D y + z x + z

1 marks

Answer: D

This question in 9701/12 Oct/Nov 2024

3 In the diagram, curve X was obtained by measuring the volume of oxygen produced during the decomposition of 100cm3 of 1.0moldm–3 hydrogen peroxide. A catalyst of manganese(IV) oxide was used. volume of oxygen formed 0 0 time Y X Which alteration to the original experimental conditions would produce curve Y? A adding more manganese(IV) oxide B adding some 0.1moldm–3 hydrogen peroxide C adding water D raising the temperature

1 marks

Answer: B

This question in 9701/11 May/June 2025

7 The gaseous compound Z decomposes on heating. In the diagram, Boltzmann distributions for Z at two different temperatures, P and Q, are shown. The lines X and Y indicate activation energies for the decomposition of Z with and without a catalyst. 0 0 molecular energy number of molecules X Y P Q Which curve and which line describe the decomposition of Z at a higher temperature and with a catalyst present? higher temperature catalyst present A P X B P Y C Q X D Q Y

1 marks

Answer: C

This question in 9701/13 May/June 2025

15 The reversible reaction between methanol and ethanoic acid liquids is catalysed by adding a small volume of concentrated sulfuric acid. Two statements about this reaction are listed. 1 The sulfuric acid is a homogeneous catalyst. 2 The sulfuric acid lowers the activation energy of the reverse reaction. Which statements are correct? A both 1 and 2 B 1 only C 2 only D neither 1 nor 2

1 marks

Answer: A

This question in 9701/11 Oct/Nov 2025