OCR GCSE Chemistry 2027 Predicted Practice Paper — Paper 3 Higher

Answer ALL questions. Write your answers in the spaces provided. You must write down all the stages in your working.

Section A

Multiple choice questions. Answer ALL the questions.

• 1

  Question SECTION-A1 (1 mark)

  Which particle has a relative mass of 1 and a relative charge of 0?

  A. ProtonB. NeutronC. ElectronD. Ion

  (Total for Question SECTION-A1 is 1 mark)
• 2

  Question SECTION-A2 (1 mark)

  An atom of an element has 17 protons, 18 neutrons and 17 electrons. What is the mass number of this atom?

  A. 17B. 18C. 34D. 35

  (Total for Question SECTION-A2 is 1 mark)
• 3

  Question SECTION-A3 (1 mark)

  Which of these is the correct electronic structure of a calcium atom (proton number 20)?

  A. 2,8,10B. 2,8,8,2C. 2,8,2,8D. 2,18

  (Total for Question SECTION-A3 is 1 mark)
• 4

  Question SECTION-A4 (1 mark)

  Sodium chloride is described as an ionic compound. Which statement best explains why solid sodium chloride does NOT conduct electricity but molten sodium chloride does?

  A. Solid sodium chloride contains no ions, but molten sodium chloride doesB. In the solid the ions are fixed in place, but when molten the ions are free to moveC. Solid sodium chloride contains free electrons that are removed on meltingD. Melting converts the ionic bonds into covalent bonds that carry charge

  (Total for Question SECTION-A4 is 1 mark)
• 5

  Question SECTION-A5 (1 mark)

  Which of the following gives the correct formula of aluminium oxide?

  A. AlOB. Al2O3C. Al3O2D. AlO2

  (Total for Question SECTION-A5 is 1 mark)
• 6

  Question SECTION-A6 (1 mark)

  A student reacts magnesium with dilute hydrochloric acid. Which pair of substances is produced?

  A. Magnesium chloride and waterB. Magnesium chloride and hydrogenC. Magnesium oxide and hydrogenD. Magnesium hydroxide and chlorine

  (Total for Question SECTION-A6 is 1 mark)
• 7

  Question SECTION-A7 (1 mark)

  Which row correctly describes the pH and nature of a solution of potassium hydroxide?

  A. pH 2, acidicB. pH 7, neutralC. pH 13, alkalineD. pH 5, acidic

  (Total for Question SECTION-A7 is 1 mark)
• 8

  Question SECTION-A8 (1 mark)

  During the electrolysis of molten lead(II) bromide, which product forms at the negative electrode (cathode)?

  A. BromineB. LeadC. HydrogenD. Oxygen

  (Total for Question SECTION-A8 is 1 mark)
• 9

  Question SECTION-A9 (1 mark)

  Which statement about an exothermic reaction is correct?

  A. It takes in energy and the surroundings get colderB. It releases energy and the surroundings get warmerC. The products have more energy than the reactantsD. There is no overall energy change

  (Total for Question SECTION-A9 is 1 mark)
• 10

  Question SECTION-A10 (1 mark)

  Which change would NOT increase the rate of a reaction between marble chips and dilute hydrochloric acid?

  A. Increasing the temperature of the acidB. Using more concentrated acidC. Using larger marble chips instead of powderD. Adding a suitable catalyst

  (Total for Question SECTION-A10 is 1 mark)
• 11

  Question SECTION-A11 (1 mark)

  Crude oil is separated into fractions by fractional distillation. Which property of the fractions increases as you move DOWN the fractionating column (towards the bottom)?

  A. Boiling pointB. FlammabilityC. Ease of ignitionD. Volatility

  (Total for Question SECTION-A11 is 1 mark)
• 12

  Question SECTION-A12 (1 mark)

  Which is the general formula for the alkanes?

  A. CnH2nB. CnH2n+2C. CnH2n-2D. CnHn

  (Total for Question SECTION-A12 is 1 mark)
• 13

  Question SECTION-A13 (1 mark)

  Bromine water is used to distinguish between an alkane and an alkene. What is observed when bromine water is added to an alkene such as ethene?

  A. It stays orangeB. It turns from orange to colourlessC. It turns from colourless to orangeD. It turns blue-black

  (Total for Question SECTION-A13 is 1 mark)
• 14

  Question SECTION-A14 (1 mark)

  Which gas is the most abundant gas in the Earth's present-day atmosphere?

  A. OxygenB. Carbon dioxideC. NitrogenD. Argon

  (Total for Question SECTION-A14 is 1 mark)
• 15

  Question SECTION-A15 (1 mark)

  The relative atomic mass of chlorine is 35.5. This value is not a whole number because:

  A. Chlorine atoms contain a non-whole number of neutronsB. Chlorine exists as a mixture of isotopes with different massesC. Chlorine gains a fraction of an electronD. The mass of the electrons must be added on

  (Total for Question SECTION-A15 is 1 mark)

Section B

Structured and extended response questions. Answer ALL the questions.

• 1

  Question SECTION-B1 (6 marks)

  Nickel can be extracted and purified using electrolysis of aqueous nickel(II) sulfate, NiSO4. Impure nickel is used as the positive electrode and a thin sheet of pure nickel as the negative electrode. (a) Write a half equation for the reaction at the negative electrode (cathode). (2 marks) (b) Explain why the mass of the positive electrode decreases during the process. (2 marks) (c) During electrolysis of aqueous nickel(II) sulfate using inert carbon electrodes instead, hydrogen is NOT produced at the cathode even though the solution contains water. Explain why nickel is deposited in preference to hydrogen. (2 marks)

  (Total for Question SECTION-B1 is 6 marks)
• 2

  Question SECTION-B2 (7 marks)

  A student carries out a titration to find the concentration of a sodium hydroxide solution. They place 25.0 cm^3 of the sodium hydroxide solution in a conical flask and add a few drops of indicator. They then add 0.100 mol/dm^3 hydrochloric acid from a burette until the end point. The mean volume of acid added was 20.0 cm^3. The equation for the reaction is: NaOH + HCl -> NaCl + H2O (a) Name a suitable indicator for this titration and state the colour change at the end point. (2 marks) (b) Calculate the number of moles of hydrochloric acid used. (2 marks) (c) Calculate the concentration of the sodium hydroxide solution in mol/dm^3. (3 marks)

  (Total for Question SECTION-B2 is 7 marks)
• 3

  Question SECTION-B3 (7 marks)

  Ammonia (NH3) is manufactured in the Haber process by reacting nitrogen and hydrogen: N2(g) + 3H2(g) <=> 2NH3(g) (the forward reaction is exothermic) The reaction is carried out at about 450 degrees C, a pressure of about 200 atmospheres and in the presence of an iron catalyst. (a) Explain, in terms of equilibrium, why a high pressure is used to increase the yield of ammonia. (3 marks) (b) Explain why a temperature of 450 degrees C is used, rather than a much lower temperature, even though a lower temperature would give a higher yield of ammonia. (3 marks) (c) State the effect of the iron catalyst on the position of equilibrium. (1 mark)

  (Total for Question SECTION-B3 is 7 marks)
• 4

  Question SECTION-B4 (7 marks)

  This question is about the reactivity of the alkali metals in Group 1 of the periodic table. A small piece of lithium, sodium and potassium is added, in separate experiments, to a trough of water containing universal indicator. (a) Describe how the reactivity of the Group 1 metals changes going down the group. (1 mark) (b) Explain, in terms of electronic structure, why reactivity changes in this way down Group 1. (3 marks) (c) Write a balanced symbol equation, including state symbols, for the reaction of potassium with water. (3 marks)

  (Total for Question SECTION-B4 is 7 marks)
• 5

  Question SECTION-B5 (8 marks)

  A student investigates the rate of reaction between sodium thiosulfate solution and dilute hydrochloric acid. When they are mixed, a pale yellow precipitate of sulfur forms and the mixture gradually turns cloudy. The student times how long it takes for a cross drawn on paper under the flask to disappear from view. The student repeats the experiment at a range of temperatures, keeping all other variables the same. (a) State the independent variable and one control variable in this investigation. (2 marks) (b) Using collision theory, explain why increasing the temperature decreases the time taken for the cross to disappear. (4 marks) (c) Suggest why this 'disappearing cross' method is not a very precise way of measuring the reaction time. (2 marks)

  (Total for Question SECTION-B5 is 8 marks)
• 6

  Question SECTION-B6 (6 marks)

  Ethanol (C2H5OH) can be produced industrially by two different methods: fermentation of sugars, and the hydration of ethene. (a) Write a word equation for the fermentation of glucose to produce ethanol. (2 marks) (b) The hydration of ethene is shown below: C2H4 + H2O -> C2H5OH State the conditions (catalyst and one other condition) needed for this reaction. (2 marks) (c) Compare the two methods by giving one advantage of producing ethanol by hydration of ethene rather than by fermentation, and one advantage of fermentation rather than hydration. (2 marks)

  (Total for Question SECTION-B6 is 6 marks)
• 7

  Question SECTION-B7 (7 marks)

  Copper(II) carbonate decomposes when heated: CuCO3 -> CuO + CO2 A student heats 12.35 g of copper(II) carbonate until it has fully decomposed. (Relative atomic masses: Cu = 63.5, C = 12, O = 16) (a) Calculate the relative formula mass (Mr) of copper(II) carbonate, CuCO3. (2 marks) (b) Calculate the number of moles of copper(II) carbonate in 12.35 g. (2 marks) (c) Calculate the mass of copper(II) oxide, CuO, produced. (3 marks)

  (Total for Question SECTION-B7 is 7 marks)
• 8

  Question SECTION-B8 (8 marks)

  The Earth's early atmosphere was very different from the atmosphere today. One theory suggests that the early atmosphere was mainly carbon dioxide, with little or no oxygen, similar to the atmospheres of Mars and Venus today. (a) Explain how the amount of carbon dioxide in the atmosphere decreased over billions of years as the oceans formed and living organisms evolved. Give two different processes. (4 marks) (b) Explain how the amount of oxygen in the atmosphere increased over time. (2 marks) (c) Human activities are now increasing the concentration of carbon dioxide and methane in the atmosphere. Explain how these greenhouse gases contribute to global warming. (2 marks)

  (Total for Question SECTION-B8 is 8 marks)
• 9

  Question SECTION-B9 (7 marks)

  Chlorine, bromine and iodine are elements in Group 7 (the halogens). (a) Chlorine gas is bubbled through a colourless solution of potassium bromide. A displacement reaction occurs and the solution turns orange. (i) Explain why chlorine is able to displace bromine from potassium bromide. (2 marks) (ii) Write a balanced symbol equation for this displacement reaction. (2 marks) (b) Explain, in terms of gaining electrons, why the reactivity of the halogens decreases going down Group 7. (3 marks)

  (Total for Question SECTION-B9 is 7 marks)
• 10

  Question SECTION-B10 (7 marks)

  Poly(ethene) is a polymer made from the monomer ethene. (a) Ethene molecules join together to form poly(ethene). Name the type of polymerisation involved and explain, in terms of the ethene molecule, why ethene is able to undergo this type of polymerisation. (3 marks) (b) Draw or describe the repeating unit of poly(ethene). (2 marks) (c) Poly(ethene) is described as non-biodegradable. Explain one environmental problem caused by disposing of poly(ethene) in landfill, and suggest one more sustainable way of dealing with waste poly(ethene). (2 marks)

  (Total for Question SECTION-B10 is 7 marks)
• 11

  Question SECTION-B11 (5 marks)

  Hydrogen is being investigated as a fuel for cars, either burned in an engine or used in a hydrogen fuel cell. When hydrogen burns in oxygen the only product is water: 2H2 + O2 -> 2H2O (a) Suggest two advantages of using hydrogen rather than petrol (a hydrocarbon) as a fuel for cars, in terms of the products formed. (2 marks) (b) A hydrogen fuel cell produces a voltage from the reaction of hydrogen and oxygen. Give one advantage and one disadvantage of using a hydrogen fuel cell in a car compared with using a rechargeable battery. (2 marks) (c) Hydrogen gas is difficult to store safely in a car. Suggest one reason why. (1 mark)

  (Total for Question SECTION-B11 is 5 marks)