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 or a graph 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 2 content: topic 1 (key concepts in chemistry) and topics 6 to 9: groups in the periodic table; rates of reaction and energy changes; fuels and Earth science; and separate chemistry 2.
- Relative atomic masses (Ar): H = 1, Li = 7, C = 12, O = 16, Ca = 40.
- One mole of any gas occupies 24 dm³ at room temperature and pressure.
Paper
Question 1 — Group 1: the alkali metals (10 marks)
(a) A small piece of potassium is added to a trough of water. Which observation is correct? [1 mark]
A it sinks and fizzes slowly B it floats, melts and burns with a lilac flame C there is no visible reaction D it sinks and a white solid forms
(b) Write the balanced equation for the reaction of sodium with water. [2 marks]
(c) Explain why potassium reacts more vigorously with water than lithium does. [3 marks]
(d) A student adds 0.35 g of lithium to excess water. The equation is 2Li + 2H₂O → 2LiOH + H₂.
Calculate the volume of hydrogen produced at room temperature and pressure. [3 marks]
(e) State the effect of the solution formed in (d) on universal indicator. [1 mark]
Question 2 — Group 7 and Group 0 (10 marks)
(a) A student adds chlorine water to colourless potassium iodide solution.
(i) Describe what the student would see. [1 mark]
(ii) Write the ionic equation for the reaction. [2 marks]
(iii) Explain, in terms of electrons, which species is oxidised in this reaction. [2 marks]
(b) Astatine is below iodine in Group 7. Predict the state and colour of astatine at room temperature. Give a reason for your prediction. [2 marks]
(c) (i) Explain why the noble gases are unreactive. [1 mark]
(ii) Argon is used to fill some filament lamps. Explain why argon is used rather than air. [2 marks]
Question 3 — Core practical: rate of reaction (10 marks)
A student adds marble chips (calcium carbonate) to excess dilute hydrochloric acid and measures the volume of carbon dioxide given off every 30 seconds.
| Time (s) | 0 | 30 | 60 | 90 | 120 | 150 | 180 |
|---|---|---|---|---|---|---|---|
| Volume of gas (cm³) | 0 | 28 | 48 | 62 | 70 | 72 | 72 |
(a) Describe how the student could collect and measure the volume of the gas. [2 marks]
(b) Calculate the mean rate of reaction in the first 60 seconds. [2 marks]
(c) Explain why the rate of reaction decreases as the reaction goes on. [2 marks]
(d) The experiment is repeated with the same mass of marble in powdered form. Describe how the results would be different. [2 marks]
(e) Calculate the mass of calcium carbonate that reacted to produce 72 cm³ of carbon dioxide at room temperature and pressure. CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ [2 marks]
Question 4 — Heat energy changes in chemical reactions (10 marks)
(a) Ammonia is made by the reaction N₂ + 3H₂ → 2NH₃.
| Bond | N–N triple bond | H–H | N–H |
|---|---|---|---|
| Bond energy (kJ/mol) | 945 | 436 | 391 |
Calculate the overall energy change for the reaction. [3 marks]
(b) Use your answer to (a) to state whether the reaction is exothermic or endothermic. Explain your answer in terms of bond breaking and bond making. [2 marks]
(c) In a core practical, a student measures the temperature change when 25 cm³ of dilute sodium hydroxide solution is neutralised by dilute hydrochloric acid. Describe how the student should carry out the experiment to get an accurate temperature change. [3 marks]
(d) Which of these reactions is endothermic? [1 mark]
A combustion of methane B neutralisation of an acid C thermal decomposition of calcium carbonate D rusting of iron
(e) State the effect of a catalyst on the activation energy of a reaction. [1 mark]
Question 5 — Fuels from crude oil (10 marks)
(a) Describe how crude oil is separated into fractions by fractional distillation. [3 marks]
(b) Tetradecane is cracked: C₁₄H₃₀ → C₈H₁₈ + 3 ______
(i) Complete the equation. [1 mark]
(ii) Give the conditions used for cracking. [2 marks]
(c) A faulty gas heater in a small room has a poor air supply. Explain why this is dangerous. [2 marks]
(d) Hydrogen can be used instead of petrol as a fuel for cars. Give one advantage and one disadvantage of using hydrogen. [2 marks]
Question 6 — The atmosphere (10 marks)
(a)* Scientists think that the Earth's early atmosphere was mainly carbon dioxide and water vapour, with very little oxygen. Today, the atmosphere is about 78% nitrogen and 21% oxygen, and contains only about 0.04% carbon dioxide.
Describe how the Earth's early atmosphere developed into the atmosphere of today. [6 marks]
(b) The concentration of carbon dioxide in the atmosphere was 317 parts per million (ppm) in 1960 and 414 ppm in 2020. Calculate the percentage increase. [2 marks]
(c) (i) Describe the test for oxygen gas. [1 mark]
(ii) Which is the approximate percentage of argon in dry air? [1 mark]
A 0.9% B 0.04% C 21% D 78%
Question 7 — Qualitative analysis: tests for ions (10 marks)
(a) A salt gives a crimson (red) flame in a flame test. Identify the metal ion in the salt. [1 mark]
(b) Sodium hydroxide solution is added to three solutions, P, Q and R.
| Solution | Observation |
|---|---|
| P | blue precipitate |
| Q | green precipitate |
| R | orange-brown precipitate |
Identify the metal ion in each solution. [3 marks]
(c) Describe a test to show that a solid contains ammonium ions. Give the result. [2 marks]
(d) (i) Describe how a student could show that a solution contains sulfate ions. [1 mark]
(ii) Explain why dilute hydrochloric acid is added before the test reagent in (d)(i). [1 mark]
(e) Acidified silver nitrate solution is added to another solution and a yellow precipitate forms.
(i) Identify the ion present. [1 mark]
(ii) Explain why the silver nitrate is acidified with dilute nitric acid rather than dilute hydrochloric acid. [1 mark]
Question 8 — Alcohols and carboxylic acids (10 marks)
(a) Give the molecular formula of propanol and name its functional group. [2 marks]
(b) Ethanol can be made by fermentation. Describe the conditions needed. [3 marks]
(c) Fermentation produces a dilute solution of ethanol. Explain how a more concentrated solution of ethanol is obtained. [2 marks]
(d) Ethanoic acid is added to sodium carbonate solution. Name the salt formed and describe what is seen. [2 marks]
(e) Which compound reacts with ethanol to form an ester? [1 mark]
A ethane B ethene C sodium chloride D ethanoic acid
Question 9 — Polymers (10 marks)
(a) Chloroethene, CH₂=CHCl, is the monomer used to make poly(chloroethene), also known as PVC. Describe the structure of the repeat unit of poly(chloroethene). [2 marks]
(b) Polyesters are condensation polymers. State two ways in which condensation polymerisation is different from addition polymerisation. [2 marks]
(c)* A local council must choose how to deal with waste plastic. It is considering three options: landfill, incineration, and collecting plastics for recycling.
Evaluate these three options. [6 marks]
Question 10 — Nanoparticles and materials (10 marks)
(a) State the size range of nanoparticles. [1 mark]
(b) Calculate the surface area to volume ratio of a cube-shaped particle with sides of 10 nm, and of one with sides of 100 nm. State how many times larger the ratio is for the smaller particle. [3 marks]
(c) Silver nanoparticles are added to some wound dressings. Explain why. [2 marks]
(d) Give one possible risk of using nanoparticles in products. [1 mark]
(e) The hulls of many small boats are made of glass-reinforced plastic (fibreglass). Explain what is meant by a composite material, and why fibreglass is suitable for a boat hull. [3 marks]