Rate of reaction — Paper 4 · IGCSE Sciences - Co-ordinated (Double) 0654

9 Magnesium is an element in Group II of the Periodic Table. (a) (i) An atom of magnesium has a mass (nucleon) number of 26. State the names and numbers of particles contained in the nucleus of this magnesium atom. … … [2] (ii) State the electronic structure of a magnesium atom. … [1] (b) Fig. 9.1 shows apparatus that a student uses to investigate the energy change when magnesium reacts with dilute hydrochloric acid. thermometer lid insulated dilute hydrochloric container acid magnesium Fig. 9.1 Fig. 9.2 shows a graph of the temperature measurements the student obtains during the investigation. BB CC temperature A 0 time Fig. 9.2 (i) Name the gas released in the reaction. … [1] (ii) Predict two ways in which the composition of the reaction mixture inside the insulated container changes during the reaction. 1 … 2 … [2] (iii) Use Fig. 9.2 to compare the average kinetic energies of the particles in the reaction mixture at points A and B, … … at points B and C. … … [1] (c) The student then investigates how the concentration of acid affects the rate of reaction between magnesium and dilute hydrochloric acid. Fig. 9.3 shows the apparatus he uses. test-tube thermometer gas syringe 50 100 excess dilute hydrochloric acid magnesium water at 20 ºC Fig. 9.3 (i) The student repeats this experiment several times using different concentrations of acid. Explain why the test-tube in Fig. 9.3 is placed in a large volume of water at 20 °C. … … … … [2] (ii) State and explain, in terms of collisions between reacting particles, the effect of an increase in acid concentration on the rate of reaction. effect … explanation … … … [2]

11 marks

Mark scheme: 9(a)(i) 12 protons ; 14 neutrons ; 2 9(a)(ii) 2,8,2 ; 1 9(b)(i) hydrogen ; 1 9(b)(ii) (concentration of) acid decreases ; (concentration of) magnesium chloride increases ; (mass of) magnesium decreases ; max 2 9(b)(iii) K.E. higher at B than at A AND K.E. at B and C the same ; 1 9(c)(i) reaction releases thermal energy / temperature of mixture increases / exothermic / temperature affects rate ; water (seeks to) keep temperature constant ; 2 9(c)(ii) reaction rate increases ; increased collision frequency ; 2

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8 Fig. 8.1 shows apparatus a student uses to collect the gas that is made when a solid reacts with a liquid. thermometer gas syringe gas collected liquid solid Fig. 8.1 Table 8.1 shows information about five experiments, P, Q, R, S and T, the student does. The temperature of the contents of the test-tube at the start of each experiment is 20 °C. Table 8.1 temperature / °C experiment liquid solid gas made at start after 2 mins dilute sodium P hydrochloric 20 17 carbon dioxide hydrogencarbonate acid dilute Q hydrochloric magnesium 20 29 acid dilute sulfuric R copper 20 20 acid S water calcium 20 32 dilute T hydrochloric calcium carbonate 20 22 acid (a) (i) Complete Table 8.1 to show the gas made, if any, in experiments Q, R, S and T. If no gas is made, state none. [3] (ii) Describe the pH changes, if any, in experiment R and in experiment S. Explain your answers. pH change in R … explanation … … pH change in S … explanation … … [2] (iii) Using Table 8.1, deduce the change in the kinetic energy of the particles in experiment P during the reaction. Explain your answer. change … explanation … … [1] (b) The student repeats experiment T several times, changing the concentration of the dilute hydrochloric acid each time. She keeps all of the other variables the same. Her results are shown as a sketch graph in Fig. 8.2. rate of reaction 0 0 concentration of hydrochloric acid Fig. 8.2 (i) Describe the relationship between the concentration of the hydrochloric acid and the rate of the reaction. … … … [2] (ii) Explain the results shown in Fig. 8.2 in terms of collisions involving particles of acid. … … … … [2] Please turn over for Question 9.

10 marks

Mark scheme: 8(a)(i) Q – hydrogen R – none S – hydrogen T – carbon dioxide 1 correct ; 2 or 3 correct ; 4 correct ; 3 8(a)(ii) R no change in pH because copper does not react with dilute sulfuric acid ; S pH increases because solution becomes alkaline / calcium hydroxide is produced ; 2 8(a)(iii) particle K. E. decreases because reaction endothermic / temperature decreases ; 1 8(b)(i) the higher the concentration (of acid) the higher the rate of reaction / proportional ; relationship is direct proportion / or description ; 2 8(b)(ii) greater concentration of acid causes greater concentration of particles ; at higher concentration of particles there is a greater collision frequency ; max 2

This question in 0654/41 Oct/Nov 2017

8 (a) For each compound shown, predict whether it reacts with water to produce an acidic, an alkaline or a neutral solution. potassium oxide, K2O … calcium oxide, CaO … carbon dioxide, CO2 … nitrogen dioxide, NO2 … [2] (b) When magnesium reacts with excess dilute hydrochloric acid, hydrogen gas is produced. Fig. 8.1 shows apparatus a student uses to investigate this reaction. hydrogen measuring cylinder gas dilute hydrochloric acid magnesium water Fig. 8.1 She measures the volume of gas in the measuring cylinder at regular intervals after the start of the reaction. A sketch graph of her results is shown in Fig. 8.2. volume of hydrogen 0 0 time Fig. 8.2 (i) Predict how the concentration of the hydrochloric acid changes, if at all, during the reaction. … [1] (ii) Describe and explain the shape of the graph in Fig. 8.2 in terms of the rate of reaction. … … … [2] (iii) The student repeats the experiment. She uses hydrochloric acid that has a higher concentration. She keeps all of the other variables the same. On Fig. 8.2, sketch a graph to show the results that the student obtains from her second experiment. [2] (c) The balanced equation for the reaction between zinc and dilute hydrochloric acid is shown. Zn + 2 HCl ZnCl + 2 H2 Complete the steps in the calculation to find the volume of hydrogen gas that is produced when 2.6 g of zinc reacts completely in excess dilute hydrochloric acid. Show your working. Step 1 Calculate the number of moles in 2.6 g of zinc. [Ar: Zn = 65] number of moles = … Step 2 State the number of moles of hydrogen gas produced. number of moles = … Step 3 Calculate the volume, in cm3, of hydrogen gas produced. [molar gas volume = 24 dm3] volume = … cm3 [4]

11 marks

Mark scheme: 8(a) potassium oxide – alkaline calcium oxide – alkaline carbon dioxide – acidic nitrogen dioxide – acidic 2 or 3 correct ; 4 correct ; 2 8(b)(i) decreases ; 1 8(b)(ii) rate of reaction, initially constant / steady ; then reaction rate decreases / eventually becomes zero ; 2 8(b)(iii) line is higher than the first line ; levels off at the same value of volume ; 2 8(c) moles of zinc = 2.6 ÷ 65 = 0.04 ; moles of hydrogen = 0.04 ; volume of hydrogen = 0.04 × 24 = 0.96 (dm3) ; 0.96 dm3 = 960 cm3 ; 4

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8 (a) Iron is a metal in the fourth period of the Periodic Table. Name the collection of metals in the fourth period that contains iron. … [1] (b) Iron is a catalyst for the industrial process that produces ammonia. (i) Name the industrial process that produces ammonia. … [1] (ii) State the gaseous elements that combine to make ammonia. … and … [1] (iii) Define the term catalyst. … … [1] (c) Potassium oxide reacts with pure water. Iron oxide does not react with pure water. (i) Suggest the pH of the mixture formed after potassium oxide reacts with water. Explain your answer. pH … explanation … … [1] (ii) State the pH of the mixture of iron oxide and water. … [1] (d) Polluted air can cause acid rain. (i) Name one gaseous oxide, other than carbon dioxide, that causes acid rain. … [1] (ii) Acid rain reacts slowly with metals and with limestone. Suggest one reason for this low rate of reaction. Explain your answer using ideas about particles. reason … … explanation … … … [2]

9 marks

Mark scheme: 8(a) transition (metals) ; 1 8(b)(i) Haber ; 1 8(b)(ii) nitrogen, hydrogen ; 1 8(b)(iii) (material) that increases reaction rate ; 1 8(c)(i) >7 to 14 AND (potassium oxide reacts to produce an) alkaline solution / potassium hydroxide ; 1 8(c)(ii) 7 ; 1 8(d)(i) sulfur dioxide ; 1 8(d)(ii) Low concentration of acid / low temperature / small surface area ; so collision frequency / chance of collision (between reactants) is low ; 2

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8 (a) Limestone is a useful material obtained from the Earth’s crust. The main compound in limestone is calcium carbonate. State two uses of limestone. 1 … 2 … [2] (b) Fig. 8.1 shows apparatus a student uses to investigate the rate of reaction between calcium carbonate and excess dilute hydrochloric acid. carbon dioxide dilute hydrochloric acid calcium carbonate electronic 75.0 g balance Fig. 8.1 The student records the balance reading every minute for 18 minutes. Fig. 8.2 shows a graph of her results. 75.0 mass / g 74.0 73.0 72.0 0 2 4 6 8 10 12 14 16 18 time / minutes Fig. 8.2 (i) Use the graph to find the time taken for all of the calcium carbonate to react. time = … minutes [1] (ii) Use the graph and your answer to (b)(i) to calculate the average loss of mass per minute until the reaction is complete. average loss of mass per minute = … g [1] (iii) The student repeats the experiment, using acid at a higher temperature. She does not change the other variables. Predict and explain the effect of this temperature increase on the rate of this reaction. Use ideas about collisions between particles in your explanation. effect … explanation … … … [2] (c) The balanced equation for the reaction in (b) is shown below. 2HCl (aq) + CaCO3(s) CaCl 2(aq) + CO2(g) + H2O(l ) (i) State the meanings of the state symbols (aq) and (l ). (aq) … (l ) … [1] (ii) Use steps 1, 2 and 3 to calculate the volume of carbon dioxide that is produced when 2.0 g of calcium carbonate reacts with excess dilute hydrochloric acid. Show your working. step 1 Calculate the number of moles of calcium carbonate contained in 2.0 g. [Ar : Ca, 40; C, 12; O, 16] number of moles of calcium carbonate = … step 2 State the number of moles of carbon dioxide that are produced. number of moles of carbon dioxide = … step 3 Calculate the volume in dm3 of carbon dioxide that is produced. [molar gas volume = 24 dm3] volume = … dm3 [4] Please turn over for Question 9.

11 marks

Mark scheme: 8(a) making, lime / calcium oxide ; neutralisation of, acidic industrial waste / acidic soil ; used in blast furnace / for iron extraction ; AVP ; max 2 8(b)(i) 12.5 ; 1 8(b)(ii) (75.0 – 72.5) ÷ 12.5 = 0.20 (g / min) ; 1 8(b)(iii) (rate increases) particles move more quickly / kinetic energy of particles increases ; which increases collision frequency / increases the chance of successful collision / more particles with activation energy ; 2 Question Answer Marks 8(c)(i) aqueous / the substance is dissolved in water / is in water solution AND liquid / the substance is a liquid ; 1 8(c)(ii) step 1 calculate Mr CaCO3 , 40 + 12 + (16 × 3) = 100 ; number of moles = 2.0 ÷ 100 = 0.02 ; step 2 moles of carbon dioxide = 0.02 ; step 3 volume of carbon dioxide = 24 × 0.02 = 0.48 (dm3 ) ; 4

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5 (a) Five elements are listed in order of reactivity. aluminium most reactive carbon iron copper gold least reactive Identify a metallic element from the list that is: extracted from its oxide in a blast furnace … obtained from its oxide by electrolysis … found in the Earth as the uncombined metal. … [2] (b) Fig. 5.1 shows apparatus a student uses to investigate the reaction between excess zinc powder and copper sulfate solution. She uses a temperature sensor to record the temperature during the investigation. zinc powder temperature sensor insulated beaker copper sulfate solution Fig. 5.1 She stirs the copper sulfate solution for one minute and then adds the zinc powder. She continues to stir the mixture for a further eight minutes. Fig. 5.2 shows a graph of the results. temperature / °C 0 2 4 6 8 10 12 time / minutes Fig. 5.2 (i) State the term used to describe all chemical reactions that cause an increase in temperature. … [1] (ii) State the energy change that occurs in the reaction between zinc and copper sulfate solution. from … to … energy energy [1] (iii) State for how long the zinc reacts with the copper sulfate solution. … minutes [1] (c) The reaction between aqueous copper ions and zinc atoms is represented by the ionic equation shown. Cu2+(aq) + Zn(s) Zn2+(aq) + Cu(s) Explain how this equation shows that zinc atoms are oxidised. … … [1] (d) The student repeats her experiment. She uses copper sulfate solution that has a higher concentration, but she does not change any other variable. State how the rate of reaction in the second experiment compares with the rate of reaction in the first experiment. Explain your answer using ideas about collisions between aqueous copper ions and zinc atoms. … … … … … [3]

9 marks

Mark scheme: 5(a) iron aluminium gold / copper 1 or 2 correct ; 3 correct ; 2 5(b)(i) exothermic ; 1 5(b)(ii) chemical (potential) to thermal ; 1 5(b)(iii) 6 ; 1 5(c) zinc atoms lose electrons ; 1 5(d) rate is higher ; higher concentration means more copper ions per volume / more ions near the zinc at any one time ; increased frequency of collision (of copper ions and zinc atoms surface) / increased chance of collisions ; 3

This question in 0654/43 Oct/Nov 2018

11 (a) A student investigates the rate of reaction of calcium carbonate with dilute hydrochloric acid. The word equation for the reaction is shown. calcium carbonate + hydrochloric acid calcium chloride + water + carbon dioxide Fig. 11.1 shows some of the apparatus he uses. calcium carbonate dilute hydrochloric acid Fig. 11.1 (i) Suggest what other equipment he needs and how he would use it to calculate the rate of carbon dioxide produced. You may draw on Fig. 11.1 to help your answer. … … … … … [2] (ii) He carries out the experiment using dilute hydrochloric acid at 20 °C. He repeats the experiment at 30 °C. Fig. 11.2 shows his results. 100 80 Keyvolume of 30 °Cgas / cm3 20 °C 60 40 20 0 0 2 4 6 8 10 12 14 16 time / min Fig. 11.2 State and explain the differences between the graphs in terms of the movement of reacting particles. … … … … … [3] (b) Lead chloride is an insoluble salt. Describe a method of making solid lead chloride from reactants chosen from Table 11.1. Table 11.1 compound solubility in water calcium chloride soluble calcium nitrate soluble calcium sulfate insoluble lead carbonate insoluble lead nitrate soluble lead sulfate insoluble magnesium sulfate soluble silver chloride insoluble sodium chloride soluble sodium nitrate soluble reactants … and … method … … … … [4] (c) Lead chloride has a melting point of 501 °C. Explain how the structure of lead chloride causes it to have a high melting point. … … … [2] [Total: 11]

11 marks

Mark scheme: 11(a)(i) gas syringe / measuring cylinder inverted over water ; measure volume of carbon dioxide and divide by time ; or balance ; measure loss in mass and divide by time ; 2 11(a)(ii) at higher temperature: (initial) rate of reaction / rate at which gas is collected, is higher ; more particles possess, activation energy / minimum energy to react, / there are more successful collisions ; greater frequency of collision ; 3 11(b) lead nitrate ; calcium chloride / sodium chloride ; mix solutions ; filter ; 4 11(c) Ionic lattice / giant ionic structure ; many bonds / strong bonds / strong forces / require a large amount of energy to break bonds ; 2

This question in 0654/41 May/June 2019

11 The raw materials needed to make sulfuric acid in the Contact process are air, sulfur and water. Fig. 11.1 shows the stages in the Contact process. sulfur air stage 1 sulfur dioxide air stage 2 sulfur trioxide sulfuric stage 3 acid compound X water stage 4 sulfuric acid Fig. 11.1 (a) In stage 2, sulfur dioxide reacts with oxygen to make sulfur trioxide. The equation for this reaction is 2SO2 + O2 2SO3 State the meaning of the symbol. … [1] (b) Fig. 11.2 shows the relationship between the temperature of stage 2 and the percentage of sulfur dioxide converted to sulfur trioxide. 100 percentage of sulfur dioxide 80 converted to sulfur trioxide 60 40 20 0 0 500 1000 1500 2000 temperature / °C Fig. 11.2 (i) Suggest the temperature in stage 2 of the Contact process. … [1] (ii) Use Fig. 11.2 to suggest one advantage, other than cost, of using a low temperature in stage 2. … [1] (iii) State and explain why a low temperature is not used in stage 2. Explain your answer in terms of particle movement in stage 2. … … … … [3] (c) Compound X, H2S2O7, is formed in stage 3. Name compound X. … [1] (d) The overall equation for the Contact process is raw materials product 2S + 3O2 + 2H2O 2H2SO4 Complete steps 1 to 4 to calculate the mass of sulfuric acid made from 1000 g of sulfur. Show your working. [Ar : H,1; O,16; S,32] Step 1 Calculate the number of moles in 1000 g of sulfur. number of moles = … Step 2 Deduce the number of moles of sulfuric acid made from 1000 g of sulfur. number of moles = … Step 3 Calculate the relative molecular mass, Mr , of sulfuric acid. Mr = … Step 4 Calculate the mass of sulfuric acid made from 1000 g of sulfur. mass = … g [4] [Total: 11]

11 marks

Mark scheme: 11(a) reversible ; 1 11(b)(i) 450 °C ; 1 11(b)(ii) greater yield / more sulfur trioxide produced ; 1 11(b)(iii) reduced rate of reaction ; any two from particles have, lower speed / less (kinetic) energy ; fewer particles have sufficient, energy to react / activation energy or fewer successful collisions ; lower frequency of collision ; max 3 11(c) oleum ; 1 11(d) Step 1: (1000 / 32) = 31.25 ; Step 2: 31.25 ; Step 3: Mr (H2SO4) = 98 ; Step 4: 31.25 × 98 = 3100 (g) ; 4

This question in 0654/42 May/June 2019

5 (a) A teacher investigates the rate at which carbon dioxide is produced when dilute hydrochloric acid reacts with excess calcium carbonate powder. She uses the apparatus shown in Fig. 5.1. The temperature of the acid is 20 °C. carbon dioxide measuring cylinder water dilute hydrochloric acid calcium carbonate Fig. 5.1 She measures the volume of carbon dioxide collected in the measuring cylinder every minute for 10 minutes. Fig. 5.2 shows a graph of her results. 0.10 0.08 volume of carbon dioxide / dm3 0.06 0.04 0.02 0 0 2 4 6 8 10 time / min Fig. 5.2 (i) Use ideas about colliding particles to explain the shape of the graph. … … … [3] (ii) The teacher repeats the experiment, adding dilute hydrochloric acid at 30 °C to excess calcium carbonate powder. Sketch the graph she obtains on Fig. 5.2. [2] (b) The symbol equation for the reaction between calcium carbonate and dilute hydrochloric acid is shown. CaCO3 + 2HCl CaCl2 + CO2 + H2O (i) State the volume of gas produced in 10 minutes when dilute hydrochloric acid at 20 °C is added to excess calcium carbonate powder. …………………………………………….. dm3 [1] (ii) Use your answer to (b)(i) to calculate the volume of dilute hydrochloric acid added to the excess calcium carbonate. Complete steps 1 to 3. Show your working. The concentration of the dilute hydrochloric acid is 0.50 mol / dm3. The volume of 1 mole of any gas is 24 dm3 at room temperature and pressure. Step 1 Calculate the number of moles of carbon dioxide produced. number of moles = … Step 2 Calculate the number of moles of HCl reacting. number of moles = … Step 3 Calculate the volume of dilute acid added. volume = … dm3 [3] (c) State the ratio of the number of molecules in 1 mole of carbon dioxide to the number of molecules in 1 mole of water. … [1] [Total: 10]

10 marks

Mark scheme: 5(a)(i) rate decreases ; acid (particles) used up / concentration decreases ; frequency of particle collision decreases ; 3 5(a)(ii) steeper initially and plateaus earlier ; same final volume ; 2 5(b)(i) 0.070 ; 1 5(b)(ii) (0.070 / 24) = 0.0029 ; (0.0029 × 2) = 0.0058 ; (0.0058 / 0.50) = 0.012 ; 3 5(c) 1:1 ; 1

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8 Calcium carbonate, CaCO3, reacts with dilute hydrochloric acid. Calcium chloride, CaCl 2, carbon dioxide and water are made. (a) Write the balanced symbol equation for this reaction. … [2] (b) The hydrochloric acid used in the experiment is made by dissolving 0.75 moles of hydrogen chloride in 500 cm3 of water. Calculate the concentration of the hydrochloric acid in mol / dm3. concentration = … mol / dm3 [2] (c) The rate of this reaction can be changed by changing the concentration of the acid. Explain the effect of changing the concentration of the acid on the rate of the reaction. Use ideas about particles. … … … … … [3] (d) The reaction between calcium carbonate and hydrochloric acid is exothermic. (i) State the meaning of an exothermic reaction. … … [1] (ii) Fig. 8.1 shows an energy level diagram for an exothermic reaction. A B energy reactants C products reaction progress Fig. 8.1 State which arrow, A, B or C, shows the activation energy for the reaction. … [1] [Total: 9]

9 marks

Mark scheme: 8(a) CaCO3 + 2HCl → CaCl2 + H2O + CO2 correct formulae ; correctly balanced ; Question Answer Marks 8(b) (0.75 × 1000) ÷ 500 ; 1.5 (mol/dm3) ; or volume of water = 0.500 dm3 ; (0.75 ÷ 0.500 =) 1.5 (mol/dm3) ; 2 8(c) higher the concentration, higher the rate of reaction ; particles are more crowded / more particles per unit volume / more particles per cm3 / increased chance of collision ; more frequent collisions / more collisions per second ; 3 8(d)(i) (reaction in which), thermal energy / heat, is given out / more energy is given out than taken in / energy of products is less than energy of reactants ; 1 8(d)(ii) B 1

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11 Ammonium sulfate is used as a fertiliser. (a) Ammonium sulfate contains the ions NH4+ and SO42–. Determine the formula of ammonium sulfate. … [1] (b) Describe why it is important that farmers use fertilisers containing nitrogen, phosphorus and potassium. … … … [2] (c) Ammonium sulfate is made by reacting dilute sulfuric acid with ammonia. Ammonia is made in the Haber process. Nitrogen gas reacts with hydrogen gas as shown in the equation. N2 + 3H2 2NH3 (i) Explain why a temperature of 450 °C is used rather than a temperature of 800 °C. Do not include cost in your answer. … … [1] (ii) Explain why a temperature of 450 °C is used rather than a temperature of 200 °C. Do not include cost in your answer. … … [1] (iii) State why iron is needed in the Haber process. … … [1] [Total: 6]

6 marks

Mark scheme: 11(a) (NH4)2SO4 ; 1 11(b) to improve crop yield / idea of producing better quality crops ; fertilisers provide the essential elements for plant growth / owtte ; plants remove NPK (from soil), which needs to be replaced / owtte ; max 2 11(c)(i) idea that 450°C gives higher yield (than 800°C) / ORA ; 1 11(c)(ii) idea that rate of reaction is faster at 450°C (than at 200°C) / ORA ; 1 11(c)(iii) iron is a catalyst / iron increases the rate of the reaction ; 1

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5 A scientist investigates the reaction between calcium carbonate and dilute hydrochloric acid. Carbon dioxide gas is given off during the reaction. The scientist measures the mass of the flask and its contents every 30 seconds during the experiment. Fig. 5.1 shows the apparatus the scientist uses. cotton wool dilute hydrochloric acid flask pieces of calcium carbonate 178.52 balance Fig. 5.1 After every reading, the scientist calculates the mass of carbon dioxide gas given off. The scientist repeats the experiment using the same amount of calcium carbonate and dilute hydrochloric acid. This time he uses warm dilute hydrochloric acid instead of cold dilute hydrochloric acid. Fig. 5.2 shows the scientist’s results. 1.2 1.1 warm acid 1.0 0.9 cold acid 0.8 mass of 0.7 carbon dioxide 0.6 / g 0.5 0.4 0.3 0.2 0.1 00 1 2 3 4 5 6 7 time / minutes Fig. 5.2 (a) (i) Use Fig. 5.2 to state the mass of carbon dioxide made after 2.5 minutes using cold acid. … [1] (ii) Warm acid reacts faster with calcium carbonate than cold acid. Explain why both reactions make 1.2 g of carbon dioxide gas. … … [1] (iii) Calculate the volume occupied by 1.2 g of carbon dioxide gas at 25 °C. The molar gas volume at 25 °C is 24 dm3. [Ar: C, 12; O, 16] volume = … dm3 [3] (b) The reaction with warm acid is faster than the reaction with cold acid. Explain why reactions are faster at higher temperatures. Explain your answer in terms of collisions between particles. … … … … [3] (c) State two other processes that produce carbon dioxide. 1 … 2 … [2] [Total: 10]

10 marks

Mark scheme: 5(a)(i) 0.9 (g) ; 1 5(a)(ii) any one from: same mass / amount of calcium carbonate ; same amount of hydrochloric acid ; 1 5(a)(iii) Mr of CO2 = 44 ; moles of CO2 = 1.2 ÷ 44 = 0.027 ; volume of CO2 = 0.027 × 24 = 0.65 dm³ ; 3 5(b) particles have more kinetic energy / particles move faster ; more collisions per second / greater collision frequency ; more particles have the minimum/activation energy to react; 3 5(c) any two from: combustion of carbon-containing substances; respiration; (thermal) decomposition of carbonate; 2

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13 Ammonia, NH3, is used in the manufacture of nitrogen‑containing fertilisers. (a) Explain why nitrogen‑containing fertilisers are important. … [1] (b) Ammonia is made in the Haber process. Fig. 13.1 shows stages in the Haber process. nitrogen from the air reaction chamber unreacted hydrogen from gases natural gas recycled liquid ammonia collected when gases cooled liquid ammonia Fig. 13.1 (i) Write a balanced symbol equation for the formation of ammonia in the Haber process. … [2] (ii) Suggest a suitable pressure to use in the reaction chamber. … [1] (iii) Explain why: • an iron catalyst • a temperature of 450 °C are used in the reaction chamber. iron catalyst … … temperature of 450 °C … … [2]

6 marks

Mark scheme: 13(a) any one from : for (good) plant growth ; to produce plant proteins / amino acids ; to produce sufficient food / increase yield AW ; 13(b)(i) N2 + 3H2 ⇌ 2NH3 correct formulae ; correctly balanced ; 2 13(b)(ii) 200 atmospheres ; 1 13(b)(iii) catalyst speeds up rate of reaction ; (temperature of) 450 °C is used to increase the rate of reaction without sacrificing yield ; 2

This question in 0654/41 Oct/Nov 2020

8 A student investigates the reaction between sodium thiosulfate solution and dilute hydrochloric acid. Fig. 8.1 shows the apparatus the student uses. min s 1 s 00:00. 10000 add dilute acid and start timing sodium thiosulfate solution cloudy mixture a cross drawn on start of end of paper experiment experiment Fig. 8.1 The student looks down at the cross drawn on the paper. A solid is made during the reaction and the mixture in the flask becomes cloudy. At the moment she adds the dilute acid, the student starts a stop-watch. She measures the time it takes until she can no longer see the cross. The student does four experiments. She uses different concentrations, A, B, C or D, of sodium thiosulfate each time. She does all the experiments at 20 °C and keeps the concentration of hydrochloric acid constant. Table 8.1 shows her results. Table 8.1 concentration time taken for cross to disappear / s A 39 B 78 C 127 D 61 (a) Look at the student’s results. State which is the most concentrated solution of sodium thiosulfate. Choose from A, B, C or D. … Explain your answer. … … [2] (b) The rate of the reaction can be increased by increasing the temperature of the reaction mixture to 45 °C. Explain why. Use ideas about collisions between particles. … … … … [3] (c) The reaction between sodium thiosulfate solution and dilute hydrochloric acid is exothermic. Explain why. Use ideas about bond forming and bond breaking. … … … … [3] [Total: 8]

8 marks

Mark scheme: 8(a) A ; fastest reaction / shortest time ; 2 8(b) particles have more kinetic energy / move faster ; more collisions per second / greater collision frequency; more particles have the, minimum / activation energy ; 3 8(c) bond breaking absorbs energy / bond breaking is endothermic ; bond making releases energy / bond making is exothermic ; more energy released than absorbed / ORA ; 3

This question in 0654/42 Oct/Nov 2020

2 Ammonium sulfate is a fertiliser. The formula of ammonium sulfate is (NH4)2SO4. (a) Calculate the relative formula mass, Mr , of ammonium sulfate. [Ar: H, 1; N, 14; O, 16; S, 32] relative formula mass = … [1] (b) Ammonium sulfate is made by reacting ammonia with sulfuric acid. Write a balanced symbol equation for this reaction. … [2] (c) Potassium sulfate, K2SO4, is another fertiliser. In an experiment, 22.4 g of potassium hydroxide, KOH, dissolved in distilled water, reacts with 19.6 g of sulfuric acid to make potassium sulfate. (i) Calculate the number of moles of potassium hydroxide and the number of moles of sulfuric acid that react. [Ar: H, 1; K, 39; O, 16; S, 32] number of moles of potassium hydroxide = … number of moles of sulfuric acid = … [2] (ii) Using your answers from part (c)(i), deduce the balanced symbol equation for the reaction. Show your working. … [3] (d) Ammonia is used in the manufacture of some fertilisers. Ammonia is made in the Haber process. nitrogen + hydrogen ammonia Fig. 2.1 shows the percentage of ammonia made using different conditions of temperature and pressure. 100 200 °C 80 400 °C 60 percentage of ammonia made 40 600 °C 20 0 0 100 200 300 400 500 pressure / atmospheres Fig. 2.1 The highest percentage of ammonia is made at 200 °C and 300 atmospheres pressure. However, in an ammonia factory, a temperature of 450 °C and 200 atmospheres pressure are used. Explain why. Use ideas about the percentage of ammonia made and the rate of reaction. … … … … … [3] [Total: 11]

11 marks

Mark scheme: 2(a) 132 ; 1 2(b) 2NH3 + H2SO4 → (NH4)2SO4 correct formulae ; correctly balanced ; 2 2(c)(i) moles of KOH = mass ÷ Mr = 22.4 ÷ 56 = 0.40 moles of H2SO4 mass ÷ Mr = 19.6 ÷ 98 = 0.20 use of mass ÷ Mr or working ; 0.40 and 0.20 ; 2 Question Answer Marks 2(c)(ii) simplest whole number ratio is 2:1 / (so) 2 mol of KOH react with 1 mol of H2SO4 ; 2KOH + H2SO4 → K2SO4 + 2H2O correct formulae ; correctly balanced ; 3 2(d) 450°C / higher temperature (rather than 200°C) increases rate of reaction ; 200 atmospheres / lower pressure (rather than 300 atmospheres) safer / less expensive ; idea of compromise (e.g. between yield and rate) ; max 3 3

This question in 0654/43 Oct/Nov 2020

8 A scientist investigates the reaction between marble chips (calcium carbonate) and dilute hydrochloric acid. The scientist uses 20 g of marble chips and 40 cm3 of dilute hydrochloric acid. The temperature of the acid is 25 °C. Fig. 8.1 shows the apparatus used. beaker 40 cm3 dilute marble hydrochloric acid chips 146.2 g balance Fig. 8.1 The scientist measures the mass every 20 seconds until the reaction stops. The scientist calculates the loss in mass. Fig. 8.2 shows the results. 0.6 0.5 0.4 loss in mass 0.3 / g 0.2 0.1 0.0 0 40 80 120 160 200 240 280 time / seconds Fig. 8.2 (a) (i) Use Fig. 8.2 to state the loss in mass after 40 seconds. loss in mass = … g [1] (ii) Use Fig. 8.2 to state how long it takes for the reaction to stop. time = … seconds [1] (b) The scientist does the experiment again. This time the scientist uses dilute hydrochloric acid which is less concentrated than in the first experiment. The reaction is slower. Explain why reactions are slower when reactants are less concentrated. Explain your answer in terms of collisions between particles. … … … [2] (c) Carbon dioxide gas is made in the reaction. State the chemical test and its positive result for carbon dioxide gas. test … result … [2] (d) In this experiment, 0.47 g of carbon dioxide gas is made. Calculate the volume occupied by 0.47 g of carbon dioxide gas. The molar gas volume at 25 °C is 24 dm3. Show your working. [Ar : C, 12; O, 16] volume = … dm3 [3] [Total: 9]

9 marks

Mark scheme: 8(a)(i) 0.3 (g) ; 1 8(a)(ii) 156 (seconds) ; 1 8(b) less particles per unit volume / less particles per cm3 / less particle density ; less frequent collisions / less collisions per second ; 2 8(c) limewater ; turns, milky / cloudy ; 2 8(d) Mr of CO2 = 44 ; moles of CO2 = 0.47 ÷ 44 = 0.0107 ; volume of CO2 = 0.0107 × 24 = 0.26 (dm³) OR volume of CO2 = 0.0107 × 24 = 0.26 (dm³) ; 3

This question in 0654/42 Feb/March 2021

8 A student is investigating indigestion tablets. Indigestion tablets neutralise excess acid in the stomach. The student adds one tablet to 50 cm3 of dilute hydrochloric acid. He measures the time taken for the tablet to completely react. The student repeats the experiment using different concentrations of hydrochloric acid. The temperature of the acid is always 25 °C. Fig. 8.1 shows the apparatus he uses. beaker 50 cm3 dilute hydrochloric acid indigestion tablet Fig. 8.1 Fig. 8.2 shows a graph of the student’s results. 200 150 time / s 100 50 0 0 0.5 1.0 1.5 2.0 concentration mol/dm3 Fig. 8.2 (a) Look at Fig. 8.2. State how long it takes for the tablet to fully react when the student uses hydrochloric acid with a concentration of 1.0 mol / dm3. time = … s [1] (b) The student does the experiment again. He makes only one change. He uses dilute hydrochloric acid at a temperature of 35 °C instead of 25 °C. Sketch a line on Fig. 8.2 to predict the results at 35 °C. [1] (c) The student’s results show that it takes less time for indigestion tablets to react when the acid is more concentrated. Explain why reactions are faster when reactants are more concentrated. Explain your answer in terms of collisions between particles. … … … [2] (d) Indigestion tablets contain calcium carbonate, CaCO3. Look at the symbol equation for the reaction of calcium carbonate with dilute hydrochloric acid. The equation is not balanced. Balance the equation. CaCO3 + HCl CaCl2 + CO2 + H2O [1] (e) In one experiment the student measures the temperature of the acid before he adds the tablet. He also measures the temperature after all the tablet has reacted. The temperature decreases. State the name for this type of energy transfer. … [1] (f) Dilute hydrochloric acid is an acid. Define an acid in terms of proton transfer. … [1] [Total: 7]

7 marks

Mark scheme: 8(a) 50 (seconds) ; 1 8(b) line is same shape as original and is always underneath it ; 1 8(c) more particles per unit volume / more particles per cm3 ; more frequent collisions / more collisions per second ; 2 8(d) CaCO3 + 2 HCl → CaCl2 + CO2 + H2O ; 1 8(e) endothermic ; 1 8(f) (acid is a) proton donor / donates protons / owtte ; 1

This question in 0654/42 May/June 2021

2 Hydrogen peroxide solution slowly decomposes to make water and oxygen gas. (a) (i) Write the word equation for this reaction. … [1] (ii) Manganese(IV) oxide is a catalyst for this reaction. Describe what is meant by a catalyst. … … … [2] (b) A student investigates the decomposition of hydrogen peroxide solution. Fig. 2.1 shows the student’s experiment. 25 cm3 beaker hydrogen peroxide solution manganese(IV) oxide 52.50 g Fig. 2.1 Fig. 2.2 shows a graph of the student’s results. 0.5 0.4 0.3 loss in mass / g 0.2 0.1 0 0 1 2 3 4 5 6 time / min Fig. 2.2 (i) State the loss in mass after 2 minutes. loss in mass = … g [1] (ii) State what happens to the rate of the reaction between 1 and 4 minutes. … [1] (c) The student wants to increase the rate of the decomposition of the hydrogen peroxide solution. He does not want to change the catalyst or the volume of the hydrogen peroxide solution. Describe and explain one way that the student can use to increase the rate of the reaction. Explain your answer in terms of collisions between particles. … … … … [3] [Total: 8]

8 marks

Mark scheme: 2(a)(i) hydrogen peroxide → water + oxygen ; 1 2(a)(ii) (substance that) speeds up a reaction / makes a reaction faster ; (substance that) is not changed at the end of the reaction / is not included in the chemical equation / is not used up ; 2 2(b)(i) 0.4 (g) ; 1 2(b)(ii) decreases / owtte ; 1 2(c) increase concentration ; (so) more particles per unit volume / more particles per cm3 ; more frequent collisions / more collisions per second ; or increase temperature ; (so) particles move faster / particles have more energy ; more frequent collisions / more collisions per second / more successful collisions ; max 3 3

This question in 0654/43 May/June 2021

2 Ammonia, NH3, is made in the Haber process. The balanced symbol equation is shown. N2 + 3H2 2NH3 Fig. 2.1 shows how ammonia is made. nitrogen and hydrogen nitrogen • iron catalyst • high pressure hydrogen • 450 °C ammonia Fig. 2.1 (a) The reaction between nitrogen and hydrogen is a reversible reaction. State what is meant by a reversible reaction. … [1] (b) Describe what happens to unreacted nitrogen and hydrogen. … [1] (c) It is important to make ammonia as cheaply as possible. The conditions used to make ammonia are an iron catalyst, a high pressure and a temperature of 450 °C. Two of the factors that affect cost are: • the percentage of ammonia made • the rate of reaction. Explain why each condition is used. Use ideas about percentage of ammonia made and the rate of reaction. iron catalyst … … high pressure … … 450 °C … … [3] (d) The atoms in a molecule of nitrogen, N2, are held together by covalent bonds. The electronic structure of nitrogen is 2,5. Draw the dot-and-cross diagram to show the bonding in nitrogen. You only need to include the outer shell electrons. [2] (e) Ammonia reacts with sulfuric acid. The balanced symbol equation is shown. 2NH3 + H2SO4 (NH4)2SO4 Calculate the mass of sulfuric acid, H2SO4, needed to react completely with 68 g of ammonia. Show your working. [Ar : H, 1; N, 14; O, 16; S, 32] mass of sulfuric acid = … g [3] [Total: 10]

10 marks

Mark scheme: 2(a) idea of a reaction that goes both ways ; 1 2(b) recycled / owtte ; 1 2(c) iron catalyst: increases rate of reaction / owtte ; high pressure: increases the yield of ammonia / increases rate of reaction ; 450 °C: idea of compromise of temperature to give high enough rate of reaction with reasonable yield ; 3 2(d) triple bond between N atoms ; lone pairs on N atoms ; 2 2(e) Mr of NH3 = 17 and Mr H2SO4 = 98 ; 2 moles of NH3 needs 1 mole of H2SO4 ; 98 68 34 × = 196 (g) ; 3

This question in 0654/41 Oct/Nov 2021

5 Magnesium carbonate, MgCO3, reacts with dilute hydrochloric acid, HCl. Magnesium chloride, MgCl 2, carbon dioxide and water are made. (a) Write the balanced symbol equation for this reaction. … [2] (b) A student investigates the reaction between magnesium carbonate and dilute hydrochloric acid. Fig. 5.1 shows the apparatus used. 20 40 60 80 100 cm3 gas syringe dilute hydrochloric acid magnesium carbonate Fig. 5.1 The student measures the total volume of carbon dioxide gas collected every 10 seconds. The student then repeats the experiment using the same amount of magnesium carbonate and the same volume of hydrochloric acid. The hydrochloric acid is more concentrated. In both experiments all of the magnesium carbonate is used up by the end of the reaction. Table 5.1 shows the student’s results. Table 5.1 time / seconds 0 10 20 30 40 50 60 70 80 dilute volume hydrochloric 0 12 25 33 40 43 46 48 48 of acid carbon dioxide concentrated in cm3 hydrochloric 0 25 38 44 46 48 48 48 48 acid (i) Look at the results for the dilute acid in Table 5.1. State how long it takes to make 33 cm3 of carbon dioxide gas. time = … seconds [1] (ii) Look at the results for both experiments in Table 5.1. The total volume of carbon dioxide gas is the same at the end of both experiments. Explain why. … [1] (iii) Describe the test for carbon dioxide gas and its positive result. test … result … [2] (iv) The volume of carbon dioxide gas made in both experiments is 48 cm3. Calculate the mass of 48 cm3 of carbon dioxide gas. The molar gas volume at 25 °C is 24 dm3. Show your working. [Ar : C, 12; O, 16] mass of carbon dioxide gas = … g [3] (c) Describe and explain the effect of increasing the concentration on the rate of reaction. Explain your answer in terms of collisions between particles. … … … … [3] [Total: 12]

12 marks

Mark scheme: 5(a) MgCO3 + 2HCl → MgCl2 + CO2 + H2O correct formulae ; correct balancing ; 2 5(b)(i) 30 (seconds) ; 1 5(b)(ii) (student used) same mass of magnesium carbonate; 1 5(b)(iii) limewater ; turns milky / cloudy ; 2 5(b)(iv) moles of CO2 = 48 ÷ 24 000 or 0.048 ÷ 24 or 0.0020 ; Mr of CO2 = 44 ; (mass of CO2 = 0.0020 × 44 =) 0.088 (g) ; 3 5(c) rate of reaction increases / owtte ; particles are more crowded / more particles per unit volume / more particles per cm3 ; more frequent collisions / more collisions per second ; 3

This question in 0654/41 Oct/Nov 2021

11 A student investigates the reaction between zinc, Zn, and dilute hydrochloric acid, HCl. Zinc chloride, ZnCl 2, and hydrogen gas are made. (a) Write the balanced symbol equation for this reaction. … [2] (b) The student does the experiment three times. The student uses dilute hydrochloric acid with the same concentration each time. Fig. 11.1 shows the student’s results. 1 2 volume of hydrogen / cm3 3 time / min Fig. 11.1 (i) State which reaction took the longest to finish. Choose from experiments 1, 2 or 3. … [1] (ii) In all three experiments the student keeps the same: • volume of dilute hydrochloric acid • concentration of dilute hydrochloric acid • size pieces of zinc. State one variable that could have been changed from experiment 1 to produce the results in experiment 2. Explain your answer. variable changed … explanation … … … [3] (iii) The student uses 1 g of zinc in experiment 1. Suggest the mass of zinc used in experiment 3. mass of zinc = … g [1] (c) Brass is an alloy made when zinc is mixed with copper. State which diagram shows the structure of brass. Choose from A, B, C or D. A B C D diagram … [1] (d) Copper metal is a good conductor of electricity. Explain why copper is a good conductor of electricity. … … … [2] [Total: 10]

10 marks

Mark scheme: 11(a) Zn + 2HCl → ZnCl2 + H2 correct formulae ; correct balancing ; 2 11(b)(i) 2 : 1 11(b)(ii) explanation for experiment 2: used a lower temperature ; any two from: particles move slower or particles have less energy ; less frequent collisions / less collisions per second ; less particles with the activation energy / enough energy to react ; 3 11(b)(iii) 0.5 (g) ; 1 11(c) D ; 1 11(d) reference to sea of electrons ; electrons can move through the structure / flow / carry charge ; 2

This question in 0654/43 Oct/Nov 2021

8 Plants need three essential elements: nitrogen, phosphorus and potassium. These elements are found in fertilisers. (a) Describe why it is important that farmers use fertilisers containing nitrogen, phosphorus and potassium. … … … [2] (b) Potassium sulfate, K2SO4, is a fertiliser that contains potassium. A student makes some potassium sulfate. He reacts potassium carbonate, K2CO3, with sulfuric acid. Look at the equation for this reaction. K2CO3 + H2SO4 K2SO4 + CO2 + H2O The student uses 2.76 g of potassium carbonate. Calculate the mass of potassium sulfate the student makes. Show your working. [Ar: C, 12; H, 1; K, 39; O, 16; S, 32] mass = … g [2] (c) Another student checks that a sample of fertiliser contains potassium. She uses a flame test. Describe how she will know if the fertiliser contains potassium. … [1] (d) Ammonia is used to make some fertilisers. Ammonia is made from nitrogen and hydrogen. N2 + 3H2 2NH3 (i) The use of a catalyst reduces the cost of making ammonia. Explain how. … … [1] (ii) The reaction between nitrogen and hydrogen is reversible. Explain what is meant by a reversible reaction. … … [1] (e) Fig. 8.1 shows the percentage of ammonia made at different temperatures and pressures. 80 70 350°C350°C 60 400°C400°C 50 percentage 450°C450°C of ammonia 40 made 30 20 10 0 0 100 200 300 400 pressure / atmospheres Fig. 8.1 Look at Fig. 8.1. (i) Describe how the percentage of ammonia made changes as the temperature increases. … [1] (ii) State a temperature and pressure which would make 40% of ammonia. temperature = … °C pressure = … atmospheres [1] [Total: 9]

9 marks

Mark scheme: 8(a) to, improve quality / increase yield / for growth, (of crop / plant) ; prevents discolouration of leaves / synthesis of (named) proteins or amino acids / replaces (named) minerals or ions in soil ; 2 8(b) relative formula mass of K2CO3 =138 and of K2SO4 = 174 ;  174 2.76 138 = 3.48 g ; 2 8(c) (flame test gives) a lilac / purple (flame) ; 1 Question Answer Marks 8(d)(i) (catalyst) increases rate of reaction ; 1 8(d)(ii) idea that reaction can go both ways / can go in both directions ; 1 8(e)(i) decreases / owtte ; 1 8(e)(ii) 350 °C and 125 atm OR 400 °C and 210 atm OR 450 °C and 325 atm ; 1

This question in 0654/42 May/June 2022

8 Fig. 8.1 shows the arrangement of ions in magnesium metal at 25°C. Fig. 8.1 (a) Describe the changes in the arrangement and movement of magnesium ions when magnesium melts. changes in arrangement of magnesium ions … … … changes in movement of magnesium ions … … … [2] (b) Magnesium melts at 650 °C and boils at 1090 °C. In the box, draw the arrangement of ions in magnesium at 1800 °C. [1] (c) Magnesium reacts with dilute hydrochloric acid. Hydrogen gas is made in the reaction. A student investigates this reaction. Fig. 8.2 shows the apparatus he uses. gas syringe magnesium ribbon dilute hydrochloric acid Fig. 8.2 Every 10 seconds, the student measures the total volume of hydrogen gas made. Fig. 8.3 shows the graph the student plots of his results. 70 60 50 volume of 40 hydrogen gas / cm3 30 20 10 0 0 10 20 30 40 50 60 70 80 time / s Fig. 8.3 (i) State the volume of gas collected after 40 seconds. volume of gas = … cm3 [1] (ii) The reaction is fastest during the first 10 seconds. Explain why. … … [1] (iii) The student repeats the experiment. He uses the same volume of hydrochloric acid and the same mass of magnesium. This time he increases the temperature of the hydrochloric acid. All of the magnesium reacts with the acid. On Fig. 8.3, sketch the shape of the graph you would expect this time. [2] (d) The rate of the reaction can be increased by increasing the concentration of the dilute hydrochloric acid. Explain why. Use ideas about collisions between particles. … … … [2] (e) Magnesium chloride is also made in the reaction between magnesium and dilute hydrochloric acid. Magnesium chloride contains the ions Mg2+ and Cl –. Determine the formula of magnesium chloride. … [1] [Total: 10]

10 marks

Mark scheme: 8(a) Changes in arrangement: idea that arrangement of particles becomes more random / becomes irregular ; Changes in movement: (idea that particles change from vibrating about fixed positions and start) moving around each other ; 8(b) randomly arranged particles not touching each other ; 1 8(c)(i) 48 (cm³) ; 1 8(c)(ii) acid is more concentrated at the start / the magnesium has a greater surface area at the start ; 1 8(c)(iii) graph steeper initially ; levels off at 58 cm³ ; 2 Question Answer Marks 8(d) more particles per unit volume / less space between particles ; increased rate of (successful) collisions ; 2 8(e) MgCl2 ; 1

This question in 0654/43 May/June 2022

11 Sulfuric acid is made by the Contact process. Sulfur, air and water are raw materials used to make sulfuric acid. Look at the equations for the first two stages in the Contact process. stage 1 … + … sulfur dioxide stage 2 sulfur dioxide + oxygen sulfur trioxide (a) Complete the word equation for stage 1 of the Contact process. [2] (b) The conditions used for stage 2 are: • 450 °C • atmospheric pressure • a catalyst. (i) State the name of the catalyst used. … [1] (ii) Explain why a catalyst and a temperature of 450 °C are used in stage 2 of the Contact process. Use ideas about: • the percentage of sulfur trioxide made • the rate of reaction. catalyst percentage of sulfur trioxide made … … rate of reaction … … 450 °C percentage of sulfur trioxide made … … rate of reaction … … [4] (c) The reaction in stage 2 of the Contact process is exothermic. Fig. 11.1 shows the energy level diagram for the reaction. Complete the labels on Fig. 11.1. Choose the labels from the list. energy given out energy taken in products reactants reactants have less energy … energy … … progress of reaction Fig. 11.1 [2] (d) In an experiment, 200 g of sulfur trioxide, SO3, is made. Calculate the volume occupied by 200 g of sulfur trioxide gas. The relative molecular mass, Mr, of sulfur trioxide is 80. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). Show your working. volume = … dm3 [2] [Total: 11]

11 marks

Mark scheme: 11(a) sulfur ; oxygen ; 2 11(b)(i) vanadium(V) oxide / vanadium pentoxide ; 1 11(b)(ii) Due to an issue with question 11(b)(ii), the question has been removed from the question paper Question Answer Marks 11(c) ;; 2 11(d) moles of SO3 = 200 ÷ 80 = 2.5 ; volume of SO3 = 2.5  24 = 60 dm³ ; 2 reactants products energy given out

This question in 0654/43 May/June 2022

5 (a) Fig. 5.1 shows the arrangement of particles in a liquid. liquid gas solid Fig. 5.1 Complete Fig. 5.1 to show the arrangement of the particles in a gas and in a solid. [2] (b) (i) Liquid water boils at 100 °C to form steam. Describe what happens to the water particles during this change of state. Include: • how the arrangement of the particles changes • how the movement of the particles changes. arrangement … … movement … … [2] (ii) Fig. 5.2 shows the bonds between the atoms and the forces between the molecules in water. H H H O O H bond between force between atoms molecules Fig. 5.2 When water boils, the forces between the molecules are broken. Explain why the bonds between atoms are not broken. … … [1] (iii) Draw a dot-and-cross diagram to show the bonding in water, H2O. Show only the outer shell electrons. [2] (c) (i) Water reacts with magnesium metal. The reaction is very slow. The reaction is faster if hot water is used. Explain why. Use ideas about collisions between particles. … … … [2] (ii) The reaction between water and magnesium is faster if powdered magnesium is used instead of strips of magnesium. Explain why. Use ideas about collisions between particles. … … … [2] [Total: 11]

11 marks

Mark scheme: 5(a) 2 gas ; solid ; 5(b)(i) move further apart ; 2 continue to move randomly / move more freely / collide with each other less often ; 5(b)(ii) bonds (between atoms) are strong / need a lot of energy to break / are covalent ; 1 5(b)(iii) 2 2 shared pairs ; all else correct ; 5(c)(i) particles move faster / have more energy ; 2 more particles possess the minimum energy to react / activation energy ; 5(c)(ii) more surface area ; 2 more frequent collisions / more collisions per second / owtte ;

This question in 0654/41 Oct/Nov 2022

8 Some cars use petrol as a fuel. Some cars use diesel as a fuel. Table 8.1 shows the mass of pollutant made when 1 kg of petrol or 1 kg of diesel is burnt in a car engine. Table 8.1 mass of pollutant / g pollutant car using petrol car using diesel black smoke 18 0.6 carbon monoxide 236 10 nitrogen monoxide 59 29 sulfur dioxide 3.8 0.9 (a) (i) Car A uses 5 kg of petrol fuel for a journey. Car B uses 8 kg of diesel fuel for the same journey. State which car, A or B, makes the most nitrogen monoxide. Explain your answer. Car … makes most nitrogen monoxide. explanation … … [1] (ii) The nitrogen monoxide, NO, made inside the car engine is removed by a catalytic converter. The nitrogen monoxide is turned into nitrogen gas and oxygen gas. Construct the balanced symbol equation for this reaction. … [2] (iii) Sulfur dioxide is a pollutant that causes acid rain. Sulfur dioxide is not removed from car emissions by a catalytic converter. Describe one way that emissions of sulfur dioxide by cars can be reduced. … … [1] (b) A petrol car makes 236 g of carbon monoxide gas when 1 kg of petrol is burnt. Calculate the volume occupied by 236 g of carbon monoxide gas. The molar gas volume at room temperature and pressure is 24 dm3. Show your working. volume = … dm3 [3] (c) Sulfur dioxide is used in the manufacture of sulfuric acid in the Contact process. 2SO2(g) + O2(g) 2SO3(g) Describe two conditions used for this reversible reaction. 1 … 2 … [2] [Total: 9]

9 marks

Mark scheme: 8(a)(i) (car A / petrol car because) 1 car A / petrol car makes 5  59 OR 295 g (of nitrogen monoxide) but car B / diesel car makes 8  29 OR 232 g (of nitrogen monoxide) ; 8(a)(ii) 2NO → N2 + O2 2 correct formulae ; correct balancing ; 8(a)(iii) use of low sulfur fuel / remove sulfur from fuel ; 1 8(b) Mr of CO = 28 ; 3 (moles of CO =) 236 ÷ 28 OR 8.43 ; (volume of CO = 8.43  24 =) 202 dm³ ; 8(c) any two from: 2 pressure – 2 atmospheres / 200 kPa ; temperature – 450 °C ; vanadium(V) oxide / V2O5 catalyst ;

This question in 0654/41 Oct/Nov 2022

3 A student reacts calcium carbonate with cold dilute hydrochloric acid. Fig. 3.1 shows the apparatus. gas syringe cold dilute hydrochloric acid calcium carbonate Fig. 3.1 The student measures the volume of gas in the gas syringe every five seconds for a total of fifty seconds. Table 3.1 shows the results. Table 3.1 time volume of gas / seconds / cm3 0 0 5 32 10 53 15 70 20 84 25 95 30 99 35 100 40 100 45 100 50 100 (a) State the volume of gas collected in the syringe when the reaction stops. volume = … cm3 [1] (b) (i) At the end of the experiment some calcium carbonate remains. Describe how the rate of reaction changes during the experiment. Explain your answer using ideas about collisions between particles. … … … … … [3] (ii) The student repeats the procedure with the same amounts of calcium carbonate and dilute hydrochloric acid. The dilute hydrochloric acid has the same concentration as in part (a). This time they use warm dilute hydrochloric acid instead of cold dilute hydrochloric acid. The reaction is much faster. Explain why the reaction is much faster by using ideas about collisions between particles. … … … … [2] (c) (i) Some buildings are made from marble. Marble is a form of calcium carbonate. Acid rain reacts very slowly with marble buildings. Suggest why the reaction is so slow. … … [1] (ii) Sulfur dioxide is a pollutant gas that dissolves in rainwater to form acid rain. State one source of sulfur dioxide in the air. … … [1] (d) Calcium carbonate, CaCO3, and dilute hydrochloric acid, HCl, react to make a gas. The other products are calcium chloride, CaCl 2, and water. Construct the balanced symbol equation for this reaction. … + … … + … + … [2] [Total: 10]

10 marks

Mark scheme: 3(a) 100 (cm3) ; 1 3(b)(i) rate of reaction decreases ; 3 as the reaction proceeds there are less particles in the same volume / less crowded particles ; therefore less collisions per second ; 3(b)(ii) particles move faster / particles have more (kinetic) energy ; 2 more (successful) collisions per second / owtte ; 3(c)(i) acid is very dilute / marble is in large pieces or has a small surface area ; 1 3(c)(ii) combustion of fossil fuels (which contain sulfur compounds) / AVP ; 1 3(d) CaCO3 + 2 HCl → CaCl2 + H2O + CO2 ;; 2

This question in 0654/42 Feb/March 2023

8 Ammonium sulfate is used as a fertiliser. (a) Ammonium sulfate contains the element nitrogen. Explain why farmers add nitrogen‑containing fertilisers to crops. … … [1] (b) Ammonium sulfate contains the ions NH4+ and SO42–. Determine the formula of ammonium sulfate. formula = … [1] (c) A student makes another fertiliser called potassium sulfate, K2SO4. The reactants are potassium hydroxide, KOH, and sulfuric acid, H2SO4. 2KOH + H2SO4 K2SO4 + 2H2O Calculate the maximum mass of potassium sulfate made from 28 g of potassium hydroxide. Show your working. [Ar: H, 1; K, 39; O, 16; S, 32] mass of potassium sulfate = … g [3] (d) Ammonia is a chemical used to make fertilisers. It is made by the Haber process from the reaction of nitrogen with hydrogen. nitrogen + hydrogen ammonia Fig. 8.1 shows the percentage of ammonia made using different conditions of temperature and pressure. 100 200 °C 80 400 °C 60 percentage of ammonia 40 600 °C 20 0 100 200 300 400 500 pressure / atmospheres Fig. 8.1 (i) State what happens to the percentage of ammonia made when the pressure increases. Use Fig. 8.1 and the curve drawn for the reaction at 600 °C. … [1] (ii) The highest percentage of ammonia is made at 200 °C and 300 atmospheres. This is the lowest of the three temperatures shown on the graph. Explain why a temperature of 450 °C is used in an ammonia factory. Use ideas about the position of the equilibrium and the rate of reaction. position of equilibrium … … rate of reaction … … [2] [Total: 8]

8 marks

Mark scheme: 8(a) increased crop yield / increased growth rate / idea of better-quality crops / idea of replacing or adding nutrients or 1 minerals / for synthesis of amino acids or proteins ; 8(b) (NH4)2SO4 ; 1 8(c) relative formula mass of KOH =56 and of K2SO4 = 174 ; 3 28 moles of KOH = = 0.5 ; 56 (2:1 ratio so) mass of potassium sulfate = 0.25  174 = 43.5 g ; 8(d)(i) increases / owtte ; 1 8(d)(ii) position of equilibrium 2 low temperature or 200 °C moves (position of) equilibrium to RHS / ORA ; rate of reaction reaction slow at low temperatures / ORA ;

This question in 0654/42 Feb/March 2023

8 A student investigates the rate of reaction between dilute hydrochloric acid, HCl, and magnesium, as shown in Fig. 8.1. Magnesium chloride, MgCl 2, and hydrogen gas, H2, are made. magnesium ribbon hydrochloric acid Fig. 8.1 (a) Construct the balanced symbol equation for this reaction. … [2] (b) The student repeats the experiment with five different temperatures of the dilute hydrochloric acid. The same volume and concentration of hydrochloric acid and the same mass of magnesium ribbon are used in each experiment. She measures the time for the magnesium to completely react at each temperature. Table 8.1 shows her results. Table 8.1 temperature time / °C / s 20 119 25 76 30 60 35 39 40 31 (i) The reaction gets faster as the temperature increases. Explain how you can tell this from Table 8.1. … [1] (ii) Tick (3) two reasons in Table 8.2 which explain why reactions get faster as the temperature increases. Table 8.2 tick reason (3) particles are closer together particles collide more often particles have less energy particles have a larger surface area particles move faster [2] (c) The reaction between magnesium and dilute hydrochloric acid is an exothermic reaction. Use the axes shown in Fig. 8.2 to draw and label the energy level diagram for this reaction. Label: • the energy of the reactants and the products • the energy change in the reaction • the activation energy of the reaction. energy progress of reaction Fig. 8.2 [3] (d) Zinc reacts with sulfuric acid, H2SO4, to make zinc sulfate, ZnSO4, and hydrogen gas. Zn + H2SO4 ZnSO4 + H2 3.35 g of zinc reacts with excess dilute sulfuric acid to make 0.1 g of hydrogen gas. Calculate the volume occupied by 0.1 g of hydrogen gas. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). volume of hydrogen gas = … dm3 [3] [Total: 11]

11 marks

Mark scheme: 8(a) Correct formulae ; Correct balancing ; 2 8(b)(i) (as the temperature increases) the time decreases / owtte ; 1 Question Answer Marks 8(b)(ii) reason tick () particles are closer together particles collide more often  particles have less energy particles have a larger surface area particles move faster  ;; 2 8(c) products shown below reactants ; energy change or H correctly labelled ; activation energy correctly labelled ; 3 Question Answer Marks 8(d) Mr of H2 = 2 ; moles of H2 = 0.1 ÷ 2 = 0.05 / M / Mr ; volume of H2 = 0.05  24 = 1.2 dm³ ; 3

This question in 0654/41 May/June 2023

2 A student investigates the reaction between calcium carbonate, CaCO3, and dilute hydrochloric acid, HCl. Calcium chloride, CaCl 2, water and carbon dioxide are made. (a) Construct the balanced symbol equation for this reaction. … [2] (b) Describe the test for carbon dioxide. Include the observation for a positive result. test … result … [2] (c) Fig. 2.1 shows the apparatus used. gas syringe conical flask calcium carbonate and dilute hydrochloric acid Fig. 2.1 The student does the experiment at five different temperatures. Table 2.1 shows the results of the experiment. Table 2.1 temperature / °C 21 32 40 48 59 time to collect 50 cm3 of gas / s 131 66 42 24 13 (i) State the temperature when the reaction is fastest. temperature = … °C [1] (ii) Describe the relationship between the temperature and the rate of the reaction. … … [1] (d) The student does the experiment again at 21 °C. They use the same amounts of calcium carbonate and dilute hydrochloric acid. This time they use hydrochloric acid that is more concentrated. The reaction is faster than when using dilute hydrochloric acid. Explain why. Use ideas about collisions between particles in your answer. … … … [2] (e) Fig. 2.2 shows the energy level diagrams for two different reactions, A and B. Reaction A and reaction B are done under the same conditions. reaction A reaction B 25 kJ energy energy 15 kJ 10 kJ 10 kJ progress of reaction progress of reaction Fig. 2.2 Reaction A happens faster than reaction B. Explain why. Use information from Fig. 2.2 in your answer. … … … [2] [Total: 10]

10 marks

Mark scheme: 2(a) correct formulae ; correct balancing ; 2 2(b) test – limewater ; result – turns milky / cloudy ; 2 2(c)(i) 59 (°C) ; 1 2(c)(ii) as the temperature increases the rate of reaction increases / owtte ; 1 2(d) particles are more crowded / more particles per cm³ / owtte ; more frequent collisions / more collisions per second / owtte ; 2 2(e) activation energy for reaction A is lower than for reaction B ; idea that more / higher proportion of reactant particles can react on collision in reaction A ; 2

This question in 0654/43 May/June 2023

8 A student investigates the reaction between large marble chips and excess dilute hydrochloric acid. Fig. 8.1 shows the apparatus they use. carbon dioxide measuring cylinder dilute hydrochloric acid trough 20 g large marble chips water Fig. 8.1 The student measures the total volume of carbon dioxide gas every 30 seconds. Fig. 8.2 shows a graph of the student’s results. 100 90 80 70 60 volume of carbon 50 dioxide gas / cm3 40 30 20 10 0 0 30 60 90 120 150 180 210 240 270 time / s Fig. 8.2 (a) (i) State the time at which the reaction stops. time = … s [1] (ii) The student repeats the experiment using 20 g of small marble chips, instead of 20 g of large marble chips. Sketch a line on Fig. 8.2 to show the results you would expect. [2] (b) The student repeats the experiment again. This time the student uses: • the same mass of small marble chips • the same volume of hydrochloric acid • more concentrated hydrochloric acid. Explain, using ideas about collisions between particles, why the reaction is faster. … … … [3] (c) The reaction between marble chips and dilute hydrochloric acid is an example of an exothermic reaction. Use the axes shown in Fig. 8.3 to draw and label the energy level diagram for this type of reaction. Label: • the energy levels of the reactants and the products • the energy change in the reaction • the activation energy of the reaction. energy progress of reaction Fig. 8.3 [3] (d) When 5 g of marble chips, CaCO3, react with dilute hydrochloric acid, HCl, 2.2 g of carbon dioxide is produced. CaCO3 + 2HCl CaCl2 + H2O + CO2 Calculate the volume occupied by this 2.2 g of carbon dioxide gas. The molar gas volume at room temperature and pressure is 24 dm3. [Ar: C, 12; O, 16] volume of carbon dioxide gas = … dm3 [3] [Total: 12]

12 marks

Mark scheme: 8(a)(i) 240 (s) ; 1 8(a)(ii) line starting at the origin but steeper than the original ; 2 levels off at 80 (cm3) ; 8(b) particles are more crowded / more particles per unit volume / 3 more particles per cm3 ; more collisions ; more frequent collisions / more collisions per second ; 8(c) 3 products shown below reactants ; energy change or H correctly clearly indicated and labelled ; activation energy clearly indicated and labelled ; 8(d) Mr of CO2 = 44 ; 3 moles of CO2 = 0.05 ; volume of H2 (= 0.05  24) = 1.2 dm3 ;

This question in 0654/42 Oct/Nov 2023

5 Some students investigate the reaction between marble chips and dilute hydrochloric acid. They react marble chips of three different sizes, A, B and C, with excess dilute hydrochloric acid. They use the same mass of marble chips, the same concentration of acid and the same temperature for each experiment. The students measure the volume of carbon dioxide gas every 30 seconds until the reaction finishes. Fig. 5.1 shows a graph of their results. 50 40 A B C 30 volume of carbon dioxide gas / cm3 20 10 0 0 30 60 90 120 150 180 210 time / s Fig. 5.1 (a) (i) State which marble chips, A, B or C, are the smallest. … [1] (ii) Look at the line for marble chips B. State when the rate of reaction is the greatest. Choose your answer from the list. 0 – 30 s 30 – 60 s 60 – 90 s 90 – 120 s answer = … s [1] (b) The students did the experiments at 20 °C. State how the rate of reaction will change if they do the experiments again at 40 °C. Explain your answer using ideas about collisions between particles. … … … … … … [3] (c) Calculate the volume occupied by 1.1 g of carbon dioxide gas at room temperature and pressure. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). [Ar: C, 12; O, 16] volume of carbon dioxide gas = … dm3 [3] (d) Carbon dioxide is a greenhouse gas. State two problems caused by increased concentrations of greenhouse gases. 1 … … 2 … … [2] [Total: 10]

10 marks

Mark scheme: 5(a)(i) A ; 1 5(a)(ii) 0–30 s ; 1 5(b) (reaction will be) faster ; (because) Any two from: molecules have higher kinetic energy / molecules are moving faster ; more molecules with activation energy ; frequency of collision (of molecules) is higher / more collisions per second ; more successful collisions ; 3 5(c) (Mr of CO2) = 12 + 16 + 16 or 44 ; (moles of CO2) = 1.1 ÷ 44 = 0.025 ; (volume of CO2) = 0.025  24 = 0.60 dm³ ; 3 5(d) Any two from: enhanced greenhouse effect ; climate change ; correct consequences e.g. altered weather patterns / colder winters / hotter summers / rising sea levels / melting of ice caps / species extinction / loss of habitat / changes to migration patterns / flooding / drought / more forest fires etc. ;; 2

This question in 0654/42 May/June 2024

11 A student investigates the reaction between calcium carbonate and dilute hydrochloric acid. Calcium chloride, water and carbon dioxide are made. CaCO3 + 2HCl CaCl 2 + H2O + CO2 The student collects and measures the volume of carbon dioxide made. (a) Suggest the apparatus the student uses to collect and measure the volume of carbon dioxide. … [1] (b) The rate of reaction between calcium carbonate and dilute hydrochloric acid is increased by increasing the temperature of the acid. Explain why. Use ideas about collisions between reacting particles. … … … … [3] (c) Calculate the mass of calcium chloride made when 20 g of calcium carbonate reacts with excess dilute hydrochloric acid. CaCO3 + 2HCl CaCl 2 + H2O + CO2 [Ar: C, 12; Ca, 40; Cl, 35.5; O, 16] mass of calcium chloride = … g [2] (d) Iron is extracted from iron ore by heating the iron ore with carbon. (i) Explain why iron can be extracted from iron ore by heating with carbon. … [1] (ii) Put a tick (✓) next to the metal that cannot be extracted from its ore by heating with carbon. aluminium copper zinc [1] (iii) Iron is extracted from iron ore in a blast furnace. Calcium carbonate (limestone) is added to the blast furnace to remove impurities in the iron ore. Complete the symbol equations to show the reactions to remove the impurities. … CaCO3 CaO + CaO + … CaSiO3 [2] (e) Iron can be coated with zinc to prevent rusting. Explain, in terms of electrons, how zinc prevents iron from rusting. … … [1] [Total: 11]

11 marks

Mark scheme: 11(a) gas syringe / measuring cylinder over water ; 1 11(b) Any 3 from particles have more kinetic energy / molecules move faster ; more particles with activation energy ; more successful collisions ; frequency of collision (of particles) is higher / more collisions per second ; 3 11(c) relative molecular mass of CaCO3 = 100 and CaCl2 = 111 / 111 20 100  = 22.2 (g) ;; 2 11(d)(i) carbon is more reactive than iron / ORA ; 1 11(d)(ii) aluminium ; 1 11(d)(iii) CO2 ; SiO2 ; 2 11(e) zinc loses electrons more readily than iron / ORA ; 1

This question in 0654/43 May/June 2024

8 A student investigates the reaction between zinc and dilute nitric acid, HNO3. Zinc nitrate, Zn(NO3)2, and hydrogen gas, H2, are made. (a) Construct the balanced symbol equation for this reaction. … [2] (b) The student performs two reactions, X and Y, using different concentrations of nitric acid. They use the same mass of zinc granules and the same temperature of nitric acid in each reaction. Fig. 8.1 shows a graph of their results. 60 50 Y volume of 40 hydrogen gas / cm3 30 20 X 10 0 0 50 100 150 200 250 300 350 time / s Fig. 8.1 (i) State which reaction, X or Y, uses a higher concentration of nitric acid. Use Fig. 8.1 to explain your answer. reaction … explanation … … … [1] (ii) Determine the average rate of reaction X during the first 50 seconds. average rate = … cm3 / s [2] (c) Reactions X and Y both produced 46 cm3 of hydrogen gas measured at room temperature and pressure (r.t.p.). Calculate the mass of 46 cm3 of hydrogen gas. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). Show your working. [Mr: H2, 2] mass of 46 cm3 of hydrogen gas = … g [3] (d) The student repeats reaction Y at a higher temperature. State and explain how the rate of reaction changes. Use ideas about collisions between particles. … … … … [3] [Total: 11]

11 marks

Mark scheme: 8(a) Zn + 2HNO3 → Zn(NO3)2 + H2 ;; 2 1 mark for correct formulae 1 mark for correct balanced equation 8(b)(i) (Y) 1 curve has a steeper gradient / reaction finishes sooner ; 8(b)(ii) (gradient calculation)16 ÷ 50 ; 2 0.32 (cm3 / s) ; 8(c) (46 cm3 =) 0.046 (dm3) ; 3 (moles of H2 = 0.046 ÷ 24 =) 0.0019 ; (mass of H2 = 2  0.0019 =) 0.0038 (g) ; 8(d) (reaction will be) faster ; 3 (because) any two from: molecules have higher (average) energy / molecules are moving faster ; more molecules with activation energy ; frequency of collision (of molecules) is higher / more collisions per second ; more successful collisions ;

This question in 0654/41 Oct/Nov 2024

8 A student investigates the reaction between calcium carbonate and dilute hydrochloric acid. The student does the experiment using three different sets of conditions, A, B and C. All other variables are kept the same. Fig. 8.1 shows the three sets of conditions. A B C thermometer 45 °C 30 °C 45 °C 0.1 mol / dm3 0.05 mol / dm3 0.1 mol / dm3 hydrochloric acid hydrochloric acid hydrochloric acid lump of calcium small pieces of powdered calcium carbonate calcium carbonate carbonate Fig. 8.1 (a) State which set of conditions, A, B or C, will give the fastest rate of reaction. … [1] (b) The equation for the reaction in the student’s experiment is shown. CaCO3 + 2HCl CaCl 2 + H2O + CO2 Calculate the mass of 1.2 dm3 of carbon dioxide gas measured at room temperature and pressure (r.t.p.). The volume of one mole of any gas is 24 dm3 at r.t.p. Show your working. [Ar: C, 12; O, 16] mass of carbon dioxide gas = … g [3] (c) The reaction between calcium carbonate and dilute hydrochloric acid is exothermic. State what is meant by an exothermic reaction. … … [1] (d) A food company is making new self-heating cans of soup. n H Ca ot ot C H ng an Self heati Self heati ng Soup Soup Creamy Creamy chicken tomato iinn 33 minuteminutess!! HHotot iinn 33 minuteminutess!! HHotot They investigate three different reactions. Fig. 8.2 shows the reaction profiles for the three reactions, X, Y and Z. X Y Z energy reactants energy energy products reactants products products reactants progress of reaction progress of reaction progress of reaction Fig. 8.2 The reaction profiles show: • the energy change in the reaction • the activation energy of the reaction. (i) State what is meant by activation energy. … … … [2] (ii) Suggest which reaction, X, Y or Z, would be most suitable to use in the self-heating cans. Explain your answer. reaction … explanation … … … [3] [Total: 10]

10 marks

Mark scheme: 8(a) C ; 1 8(b) (Mr of CO2 =) 44 ; 3 (moles of CO2 = 1.2 ÷ 24 =) 0.05 ; (mass of CO2 = 0.05  44 =) 2.2 (g) ; 8(c) (reaction in which) energy is given out / heat is given out ; 1 8(d)(i) minimum amount of energy ; 2 required for reaction to take place ; 8(d)(ii) (reaction) X ; 3 (because) Z is endothermic / Z does not give out heat (energy) ; (because) X has a lower activation energy than Y / X gives out more energy / heat than Y ;

This question in 0654/42 Oct/Nov 2024

5 A student investigates the reaction between calcium carbonate and dilute hydrochloric acid. Fig. 5.1 shows the apparatus the student uses. gas syringe dilute calcium hydrochloric acid carbonate Fig. 5.1 The student measures the volume of gas in the gas syringe every 20 seconds. Fig. 5.2 shows a graph of the student’s results. 60 50 40 volume of gas in the syringe 30 / cm3 20 10 0 0 20 40 60 80 100 120 140 160 180 time / s Fig. 5.2 (a) State the name of the gas made in this reaction. … [1] (b) Complete the sentence. The reaction is fastest between … seconds and … seconds. [1] (c) The total volume of gas made in the experiment is 50 cm3. Calculate the total number of moles in 50 cm3 of the gas measured at room temperature and pressure (r.t.p.). The volume of one mole of any gas is 24 dm3 at r.t.p. Show your working. number of moles in 50 cm3 of the gas = … [2] (d) The student repeats the experiment using dilute hydrochloric acid at a higher temperature. Explain why the reaction is faster. Use ideas about collisions between particles. … … … … … … [3] (e) The reaction between calcium carbonate and dilute hydrochloric acid is exothermic. Complete Fig. 5.3 to show an energy level diagram for an exothermic reaction. Label the activation energy and the energy change on your diagram. reactants energy progress of reaction Fig. 5.3 [3] [Total: 10]

10 marks

Mark scheme: 5(a) carbon dioxide ; 1 5(b) the reaction is fastest between 0 seconds and 16 seconds ; 1 5(c) (50 cm3 =) 0.050 dm3 ; 2 (moles = 0.050 ÷ 24) = 0.0021 ; OR (24 dm3 =) 24 000 cm3 ; moles = (50 / 24000 =) 0.0021 ; 5(d) molecules have higher (average) energy / 3 molecules are moving faster ; more molecules with activation energy ; frequency of collision (of molecules) is higher / more collisions per second / more successful collisions ; 5(e) 3 products shown below reactants ; energy change or H correctly clearly indicated and labelled ; activation energy clearly indicated and labelled ;

This question in 0654/43 Oct/Nov 2024

6 Magnesium reacts with dilute hydrochloric acid. Magnesium chloride and hydrogen gas are made. (a) Construct the balanced symbol equation for this reaction. … [2] (b) Five students investigate the rate of the reaction between magnesium and dilute hydrochloric acid. They each have a test tube containing 1.0 g magnesium and 10 cm3 of dilute hydrochloric acid. They drop the magnesium into the dilute hydrochloric acid and time how long it takes for the reaction to stop. Table 6.1 shows their results. Table 6.1 student 1 2 3 4 5 time / s 242 256 202 300 270 (i) State which student’s reaction is the fastest. student … [1] (ii) Each student had 1.0 g of different sized pieces of magnesium. State which student had the pieces of magnesium with the smallest surface area. student … [1] (c) Student 1 repeats their experiment at a lower temperature. The reaction is slower. Explain why the reaction is slower, using collision theory. … … … … [3] (d) The reaction between magnesium and dilute hydrochloric acid is exothermic. Fig. 6.1 shows the reaction pathway diagram for the reaction. A … energy reactants B … C … reaction progress Fig. 6.1 Complete the labels, A, B and C, on Fig. 6.1. [3] [Total: 10]

10 marks

Mark scheme: 6(a) Mg + 2HCl → MgCl2 + H2 ; ; 2 6(b)(i) (student) 3 ; 1 6(b)(ii) (student) 4 ; 1 6(c) any three from: 3 molecules have lower (average) energy / molecules are moving slower fewer molecules with activation energy frequency of collision of molecules is, lower / fewer, collisions per second less successful collisions ; ; ; 6(d) A - Activation energy ; 3 B - Enthalpy change; C - Products ;

This question in 0654/42 Feb/March 2025

8 A student reacts hydrochloric acid with sodium carbonate. (a) The reaction is exothermic. State what is meant by an exothermic reaction. … … [1] (b) Fig. 8.1 shows the reaction pathway diagram for the reaction. 80 70 60 50 energy reactants 40 kJ / mol 30 20 10 products 0 reaction progress Fig. 8.1 (i) State the activation energy for the reaction. activation energy = … kJ / mol [1] (ii) State the enthalpy change for the reaction. enthalpy change = … kJ / mol [2] (c) The student repeats the experiment using a catalyst. State the effect of using a catalyst on the activation energy for the reaction. … [1] (d) The student repeats the experiment at a higher temperature. The reaction is faster. Explain why, using collision theory. … … … … … [3] (e) The reaction makes sodium chloride solution, water and carbon dioxide. Complete the state symbols in the balanced chemical equation. 2HCl (aq) + Na2CO3(s) 2NaCl ( … ) + H2O ( … ) + CO2 ( … ) [2] [Total: 10]

10 marks

Mark scheme: 8(a) (reaction that) transfers / releases thermal energy to the surroundings; 1 8(b)(i) 34 (kJ/ mol); 1 8(b)(ii) 36 (kJ/ mol); 2 –; 8(c) decreases / AW; 1 8(d) any three from: 3 molecules have higher (average) kinetic energy / molecules are moving faster; more molecules / collisions with (energy greater than or equal to) activation energy; more successful collisions; 8(e) NaCl (aq) 2 H2O (l) CO2 (g);;

This question in 0654/43 May/June 2025

7 A student investigates the decomposition of hydrogen peroxide, H2O2. The equation for the reaction is shown. 2H2O2(aq) 2H2O(l) + O2(g) (a) Describe a test and its positive result to identify the gas made in the reaction. test … result … [2] (b) The student uses manganese(IV) oxide as a catalyst in the reaction. The catalyst speeds up the reaction. State why the catalyst speeds up the reaction. … … … [1] (c) The student measures the total volume of gas made every minute. The student does the experiment using manganese(IV) oxide powder. The student repeats the experiment using manganese(IV) oxide lumps. Fig. 7.1 shows a graph of the student’s results. 60 A 50 B total 40 volume of gas / cm3 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 time / min Fig. 7.1 State which line, A or B, shows the results using manganese(IV) oxide powder. Use the graph to explain your answer. line … explanation … … … … … [2] (d) The decomposition of hydrogen peroxide is highly exothermic. (i) Complete Fig. 7.2 to show an energy level diagram for the reaction. Label the activation energy and the energy change (enthalpy change) on your diagram. energy 2H2O + O2 progress of reaction Fig. 7.2 [3] (ii) Suggest the enthalpy change, ΔH, for the decomposition reaction. Tick (3) one box. +56 kJ / mol +219 kJ / mol 0 kJ / mol −196 kJ / mol [1] [Total: 9]

9 marks

Mark scheme: 7(a) test: glowing splint ; 2 result: relights ; 7(b) (catalyst) decrease the activation energy (of the reaction) / (catalyst) decrease the Ea (of the reaction) ; 1 7(c) (line A) 2 the line is steeper / line has larger gradient ; higher rate of reaction / reaction is faster / the reaction finishes first / volume of gas increases faster ; 7(d)(i) 3 reactants line drawn above products line ; arrow correctly labelled activation energy ; arrow correctly labelled energy change ; 7(d)(ii) 1 +56 kJ / mol +219 kJ / mol 0 kJ / mol –196 kJ / mol ✓

This question in 0654/43 Oct/Nov 2025