Total marks: 100 · Duration: 105 minutes · Tier: Higher
Instructions to candidates
- Use black ink or ball-point pen.
- Answer all questions.
- In calculations, show all your working and give the unit of your answer.
- You may use a calculator.
- For multiple-choice parts, choose one answer, A, B, C or D.
- Where a question describes apparatus in words, you may find it helpful to sketch it.
Information
- The total mark for this paper is 100.
- The marks for each question are shown in brackets.
- In questions marked with an asterisk (*), marks will be awarded for your ability to structure your answer logically, showing how the points that you make are related or follow on from each other where appropriate.
- This paper covers Edexcel GCSE (9–1) Chemistry Paper 1 content, topics 1 to 5: key concepts in chemistry; states of matter and mixtures; chemical changes; extracting metals and equilibria; and separate chemistry 1.
- Relative atomic masses (Ar): H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35.5, Ti = 48, Cu = 63.5, Zn = 65.
- One mole of any gas occupies 24 dm³ at room temperature and pressure. The Avogadro constant is 6.02 × 10²³ per mole.
Paper
Question 1 — Atomic structure and the periodic table (10 marks)
(a) Which particle has a relative charge of −1 and a relative mass of 1/1836? [1 mark]
A proton B neutron C electron D nucleus
(b) Magnesium has three naturally occurring isotopes: 79% magnesium-24, 10% magnesium-25 and 11% magnesium-26.
Calculate the relative atomic mass of magnesium. Give your answer to 1 decimal place. [2 marks]
(c) Explain why the isotopes of magnesium have the same chemical properties. [1 mark]
(d) An aluminium ion is represented as ²⁷₁₃Al³⁺. Give the numbers of protons, neutrons and electrons in this ion. [2 marks]
(e) Mendeleev arranged the elements in order of increasing relative atomic mass, but he placed tellurium (Ar 127.6) before iodine (Ar 126.9).
Explain why he did this, and why the modern periodic table supports his decision. [2 marks]
(f) An atom of element X has the electronic configuration 2.8.8.2. State the group and the period of element X in the periodic table. [2 marks]
Question 2 — Bonding, structure and properties (10 marks)
(a) Potassium reacts with oxygen to form potassium oxide, K₂O. Describe, in terms of electrons, how potassium oxide is formed from potassium atoms and an oxygen atom. [3 marks]
(b) Buckminsterfullerene, C₆₀, and diamond are both forms of carbon. Explain why C₆₀ has a much lower melting point than diamond. [2 marks]
(c) Describe the structure and bonding in a metal. [2 marks]
(d) Give one limitation of using a dot-and-cross diagram to represent a molecule. [1 mark]
(e) Explain why poly(ethene) has a much higher melting point than ethene. [2 marks]
Question 3 — Formulae and calculations (10 marks)
(a) A 3.0 g sample of a hydrocarbon contains 2.4 g of carbon and 0.6 g of hydrogen.
(i) Calculate the empirical formula of the hydrocarbon. [3 marks]
(ii) The relative formula mass of the hydrocarbon is 30. Deduce its molecular formula. [1 mark]
(b) Copper carbonate decomposes when heated:
CuCO₃ → CuO + CO₂
A student heats 12.35 g of copper carbonate until it has completely decomposed.
(i) Calculate the mass of copper oxide formed. [3 marks]
(ii) The student heats the copper carbonate in an open boiling tube. Explain why the mass of the tube and its contents decreases. [1 mark]
(c) Calculate the number of water molecules in 0.25 mol of water. Give your answer in standard form. [2 marks]
Question 4 — States of matter and separating mixtures (10 marks)
(a) Explain, in terms of particles, what happens when a solid melts. [2 marks]
(b) A substance has a melting point of −39 °C and a boiling point of 357 °C. Predict its state at 25 °C. [1 mark]
(c) In a core practical, a student uses simple distillation to obtain the solvent from a sample of ink. Describe how simple distillation separates the solvent from the ink. [3 marks]
(d) The student then uses paper chromatography to analyse the dyes in the ink.
(i) A dye spot moves 2.1 cm from the start line and the solvent front moves 7.0 cm. Calculate the Rf value of the dye. [2 marks]
(ii) Explain why the student concludes that another dye in the ink is a pure substance because it produces only one spot in several different solvents. [1 mark]
(e) Explain why distilled water, not tap water, is used in chemical analysis. [1 mark]
Question 5 — Acids, alkalis and salts (10 marks)
(a) In a core practical, a student adds calcium hydroxide powder, 0.10 g at a time, to 50 cm³ of dilute hydrochloric acid. The student measures the pH after each addition. The pH starts at 1 and finishes at 12.
(i) Describe and explain how the pH changes during the experiment. [2 marks]
(ii) Name the salt formed. [1 mark]
(b) A solution of hydrochloric acid has a pH of 1. It is diluted so that the hydrogen ion concentration is 10 times lower. State the new pH. [1 mark]
(c) Which of these salts is insoluble in water? [1 mark]
A sodium chloride B barium sulfate C potassium nitrate D ammonium carbonate
(d) Describe how a student could prepare a pure, dry sample of insoluble lead iodide from solutions of lead nitrate and potassium iodide. [3 marks]
(e) Write a balanced equation for the reaction between calcium hydroxide, Ca(OH)₂, and hydrochloric acid. [2 marks]
Question 6 — Electrolysis (10 marks)
(a)* In a core practical, a student investigates how the current affects the change in mass of copper electrodes during the electrolysis of copper sulfate solution.
Describe a method the student could use, and explain the change in mass at each electrode. [6 marks]
(b) Sodium chloride solution is electrolysed using inert electrodes.
(i) Name the product at the cathode. [1 mark]
(ii) Name the product at the anode. [1 mark]
(iii) Name the solution that remains at the end. [1 mark]
(iv) Write the half equation for the reaction at the anode. [1 mark]
Question 7 — Reactivity and extracting metals (10 marks)
(a) A student tests three metals, P, Q and R, with cold water and with dilute acid.
| Metal | Cold water | Dilute acid |
|---|---|---|
| P | reacts vigorously | not tested (dangerous) |
| Q | no reaction | bubbles slowly |
| R | no reaction | no reaction |
Put the metals in order of reactivity, most reactive first. [1 mark]
(b) Magnesium displaces iron from iron(II) sulfate solution. Write the ionic equation for this reaction, and identify the species that is oxidised. [2 marks]
(c) Explain why some metals are extracted by electrolysis, while others are extracted by heating their oxides with carbon. [2 marks]
(d) Copper can be extracted from soil containing low concentrations of copper compounds by phytoextraction. Give one advantage and one disadvantage of phytoextraction. [2 marks]
(e) Give two reasons why aluminium cans should be recycled rather than thrown away. [2 marks]
(f) Explain why gold is found in the Earth as the uncombined element. [1 mark]
Question 8 — Equilibria, the Haber process and fertilisers (10 marks)
Ammonia is manufactured by the Haber process:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) (the forward reaction is exothermic)
(a) Name the catalyst used in the Haber process. [1 mark]
(b) The table shows the percentage of ammonia in the equilibrium mixture at 450 °C and different pressures.
| Pressure (atm) | 100 | 200 | 300 | 400 |
|---|---|---|---|---|
| Ammonia at equilibrium (%) | 16 | 27 | 35 | 41 |
(i) Describe the trend in the data and explain it. [2 marks]
(ii) Suggest two reasons why a pressure of about 200 atm is used, rather than 400 atm. [2 marks]
(c) Ammonium sulfate is used as a fertiliser. Compare how ammonium sulfate is made in a school laboratory with how it is made in industry. [3 marks]
(d) Write a balanced equation for the reaction of ammonia with nitric acid, HNO₃, to make ammonium nitrate. [1 mark]
(e) Explain why farmers use fertilisers containing nitrogen, phosphorus and potassium. [1 mark]
Question 9 — Quantitative chemistry (10 marks)
(a) A student makes ammonium sulfate. The theoretical yield is 13.2 g. The student obtains 10.56 g.
(i) Calculate the percentage yield. [2 marks]
(ii) Give one reason why the actual yield is less than the theoretical yield. [1 mark]
(b) Titanium is extracted from titanium(IV) chloride using sodium:
TiCl₄ + 4Na → Ti + 4NaCl
Calculate the percentage atom economy for making titanium by this reaction. Give your answer to 3 significant figures. [2 marks]
(c) Zinc reacts with excess dilute hydrochloric acid:
Zn + 2HCl → ZnCl₂ + H₂
Calculate the volume of hydrogen, at room temperature and pressure, produced from 1.30 g of zinc. [2 marks]
(d) In a titration, 25.0 cm³ of potassium hydroxide solution is neutralised by 18.75 cm³ of 0.200 mol/dm³ hydrochloric acid.
KOH + HCl → KCl + H₂O
Calculate the concentration of the potassium hydroxide solution in mol/dm³. [3 marks]
Question 10 — Transition metals, corrosion and cells (10 marks)
(a) Give one property of transition metals that is not shown by Group 1 metals. [1 mark]
(b) Iron for fence posts is galvanised by coating it with zinc. Explain how galvanising protects the iron from rusting, even when the zinc coating is scratched. [2 marks]
(c) Explain why gold used for jewellery is usually an alloy with copper or silver, rather than pure gold. [1 mark]
(d)* A car manufacturer is deciding whether to power a new model with a hydrogen–oxygen fuel cell or with rechargeable batteries (chemical cells).
Evaluate the strengths and weaknesses of hydrogen–oxygen fuel cells for powering cars, compared with rechargeable batteries. [6 marks]