WJEC/Eduqas GCSE Chemistry 2027 Predicted Practice Paper — Component 1

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

Section A

Short-answer and structured questions. Answer ALL questions.

• 1

  Question SECTION-A1 (4 marks)

  An atom of an element M is represented as 39-M-19 (mass number 39, atomic number 19). (a) State the number of protons, neutrons and electrons in one atom of M. (3 marks) (b) M reacts vigorously with cold water. State which group of the periodic table M belongs to. (1 mark)

  (Total for Question SECTION-A1 is 4 marks)
• 2

  Question SECTION-A2 (5 marks)

  Magnesium reacts with chlorine to form magnesium chloride. (a) Give the electronic structure (electron configuration) of a magnesium atom. (1 mark) (b) Describe, in terms of electron transfer, how a magnesium atom and chlorine atoms form ions when magnesium chloride is produced. State the formula of each ion formed. (3 marks) (c) Give the formula of magnesium chloride. (1 mark)

  (Total for Question SECTION-A2 is 5 marks)
• 3

  Question SECTION-A3 (5 marks)

  Calcium carbonate decomposes when heated: CaCO3 -> CaO + CO2. A sample of 25.0 g of calcium carbonate is heated until it fully decomposes. (Relative atomic masses: Ca = 40, C = 12, O = 16.) (a) Calculate the relative formula mass (Mr) of calcium carbonate. (1 mark) (b) Calculate the number of moles of calcium carbonate in 25.0 g. (1 mark) (c) Calculate the mass of calcium oxide (CaO) produced. (3 marks)

  (Total for Question SECTION-A3 is 5 marks)
• 4

  Question SECTION-A4 (4 marks)

  A student investigates the rate of reaction between marble chips (calcium carbonate) and dilute hydrochloric acid by measuring the volume of gas collected over time. (a) Name the gas produced. (1 mark) (b) The student repeats the experiment using the same mass of marble but as a fine powder instead of large chips, keeping everything else the same. State and explain the effect this has on the rate of reaction. (3 marks)

  (Total for Question SECTION-A4 is 4 marks)
• 5

  Question SECTION-A5 (6 marks)

  Molten lead(II) bromide (PbBr2) is electrolysed using inert graphite electrodes. (a) Explain why lead(II) bromide must be molten (rather than solid) for electrolysis to occur. (2 marks) (b) Name the product formed at the negative electrode (cathode) and write the half-equation for its formation. (2 marks) (c) Name the product formed at the positive electrode (anode) and write the half-equation for its formation. (2 marks)

  (Total for Question SECTION-A5 is 6 marks)
• 6

  Question SECTION-A6 (4 marks)

  A student is given a colourless solution and must decide whether it is acidic, neutral or alkaline. (a) Name a suitable indicator and state the colour it turns in an alkaline solution. (2 marks) (b) Sulfuric acid reacts with sodium hydroxide solution. Write a balanced symbol equation for this neutralisation reaction, including state symbols. (2 marks)

  (Total for Question SECTION-A6 is 4 marks)
• 7

  Question SECTION-A7 (5 marks)

  In a titration, 25.0 cm^3 of sodium hydroxide solution is exactly neutralised by 20.0 cm^3 of 0.100 mol/dm^3 hydrochloric acid. The equation is: NaOH + HCl -> NaCl + H2O. (a) Calculate the number of moles of hydrochloric acid used. (2 marks) (b) Determine the number of moles of sodium hydroxide that reacted. (1 mark) (c) Calculate the concentration of the sodium hydroxide solution in mol/dm^3. (2 marks)

  (Total for Question SECTION-A7 is 5 marks)
• 8

  Question SECTION-A8 (4 marks)

  Chlorine, bromine and iodine are elements in Group 7 of the periodic table. (a) Describe the trend in reactivity of the halogens as you go down Group 7, and explain this trend in terms of electron gain. (3 marks) (b) Predict what you would observe when chlorine solution is added to potassium bromide solution. (1 mark)

  (Total for Question SECTION-A8 is 4 marks)
• 9

  Question SECTION-A9 (7 marks)

  Ammonia is manufactured in the Haber process: N2 + 3H2 -> 2NH3. In one reaction, 28.0 g of nitrogen is reacted with excess hydrogen and 27.2 g of ammonia is obtained. (Relative atomic masses: H = 1, N = 14.) (a) Calculate the maximum (theoretical) mass of ammonia that could be produced from 28.0 g of nitrogen. (4 marks) (b) Calculate the percentage yield of ammonia for this reaction. (2 marks) (c) The Haber process is carried out at a moderate temperature of about 450 degrees C rather than a very high temperature. Give one reason why a very high temperature is not used, in terms of the yield of ammonia. (1 mark)

  (Total for Question SECTION-A9 is 7 marks)
• 10

  Question SECTION-A10 (5 marks)

  Ethane (C2H6) and ethene (C2H4) are both hydrocarbons. (a) State what is meant by the term 'hydrocarbon'. (1 mark) (b) Ethene is an unsaturated hydrocarbon. Explain what 'unsaturated' means and describe a chemical test, with its result, that distinguishes ethene from ethane. (3 marks) (c) Ethene can be used to make poly(ethene). Name the type of reaction used to make poly(ethene) from ethene. (1 mark)

  (Total for Question SECTION-A10 is 5 marks)
• 11

  Question SECTION-A11 (5 marks)

  The combustion of methane can be represented by the equation: CH4 + 2O2 -> CO2 + 2H2O. The bond energies (in kJ/mol) are: C-H = 413, O=O = 498, C=O = 805, O-H = 464. (a) Calculate the total energy required to break all the bonds in the reactants. (2 marks) (b) Calculate the total energy released when all the bonds in the products are formed. (1 mark) (c) Calculate the overall energy change for the reaction and state whether it is exothermic or endothermic. (2 marks)

  (Total for Question SECTION-A11 is 5 marks)
• 12

  Question SECTION-A12 (4 marks)

  The combustion of fossil fuels releases carbon dioxide into the atmosphere. (a) Explain how an increasing concentration of carbon dioxide in the atmosphere contributes to global warming. (2 marks) (b) State one possible environmental consequence of global warming, and give one method by which carbon dioxide emissions from vehicles could be reduced. (2 marks)

  (Total for Question SECTION-A12 is 4 marks)

Section B

Extended response questions. Answer ALL questions.

• 1

  Question SECTION-B1 (8 marks)

  Metals are extracted from their ores by different methods depending on their reactivity. Iron is extracted from iron(III) oxide in a blast furnace by reduction with carbon, whereas aluminium is extracted from aluminium oxide by electrolysis. Explain, with reference to the reactivity series, why iron can be extracted by reduction with carbon but aluminium cannot, and describe why the electrolysis of aluminium oxide is an expensive process. Include a balanced symbol equation for the reduction of iron(III) oxide by carbon. (This question assesses the quality of your extended written communication.)

  (Total for Question SECTION-B1 is 8 marks)
• 2

  Question SECTION-B2 (8 marks)

  A student investigates how temperature affects the rate of reaction between sodium thiosulfate solution and dilute hydrochloric acid. When the two are mixed a pale yellow precipitate of sulfur forms, making the mixture turn cloudy. The student measures the time taken for a cross drawn under the flask to disappear from view, repeating the experiment at several temperatures. Describe how the rate of reaction changes as temperature increases, and explain this change fully using collision theory. Explain why measuring the time for the cross to disappear is a valid way to compare the rate at different temperatures, and identify two variables that must be controlled for a fair test. (This question assesses the quality of your extended written communication.)

  (Total for Question SECTION-B2 is 8 marks)
• 3

  Question SECTION-B3 (6 marks)

  Hydrogen fuel cells and rechargeable batteries can both be used to power electric vehicles. A hydrogen fuel cell produces electricity from the reaction: 2H2 + O2 -> 2H2O. Compare the use of a hydrogen fuel cell with a conventional rechargeable battery for powering a vehicle. In your answer, refer to the product(s) of the fuel cell reaction, one advantage and one disadvantage of using hydrogen fuel cells, and one environmental consideration relating to how the hydrogen is produced. (This question assesses the quality of your extended written communication.)

  (Total for Question SECTION-B3 is 6 marks)