WJEC A-Level Chemistry Unit 3, June 2025
Every question from WJEC A-Level Chemistry Unit 3, June 2025 (1410): 10 questions, 80 marks, each with its mark scheme and topic.
- Question 1 1 mark
Complete the Arrhenius equation for the rate constant k.
Physical Chemistry · 3.5 Chemical kinetics
- Question 2 1 mark
State why silicon tetrachloride reacts vigorously with water whereas carbon tetrachloride does not.
Inorganic Chemistry · 3.3 Chemistry of the p-block
- Question 3 2 marks
Define the term heterogeneous catalyst and give an example of one along with the reaction it catalyses.
Physical Chemistry · Inorganic Chemistry · 2.2 Rates of reaction · 3.4 Chemistry of the d-block transition metals
- Question 4 1 mark
Write the overall ionic equation for the oxidation of ethanedioic acid by acidified manganate(VII) ions using the provided half-equations.
Physical Chemistry · 1.1 Formulae and equations · 3.2 Redox reactions
- Question 5 2 marks
Identify a metal halide and give reasons based on a lilac flame test and the reaction with concentrated sulfuric acid yielding rotten egg smell and coloured fumes.
Inorganic Chemistry · Practical · 1.6 The Periodic Table · AS Unit 1 practical work
- Question 6 3 marks
State observations for adding excess aqueous sodium hydroxide to chromium(III) chloride, identify components of an electrochemical cell measuring standard electrode potential, and determine electron flow.
Inorganic Chemistry · Physical Chemistry · 3.1 Redox and standard electrode potential · 3.4 Chemistry of the d-block transition metals
- Question 7 16 marks
A structured question assessing thermodynamic decomposition of Group 2 nitrates (entropy and enthalpy using Gibbs free energy), solution enthalpies and solubility of sulfates, pH of ammonium nitrate, tests for lead(II) ions, and a gas-mixture calculation using the ideal gas equation to determine percentage by mass.
Physical Chemistry · Inorganic Chemistry · 1.3 Chemical calculations · 1.6 The Periodic Table · 3.3 Chemistry of the p-block · 3.6 Enthalpy changes for solids and solutions · 3.7 Entropy and feasibility of reactions · 3.9 Acid-base equilibria
- Question 8 13 marks
Write the disproportionation equation for chlorine with concentrated sodium hydroxide, explain quenching and half-life for a second order reaction, and use a concentration-time graph to determine the initial rate and rate constant.
Inorganic Chemistry · Physical Chemistry · 3.2 Redox reactions · 3.3 Chemistry of the p-block · 3.5 Chemical kinetics
- Question 9 19 marks
Calculate reaction enthalpy using formation data, explain the common ion effect on ethanoic acid, calculate pH and plan buffer preparation, and determine Kc and reaction thermochemistry for a ruthenium-catalysed equilibrium.
Physical Chemistry · 1.7 Simple equilibria and acid-base reactions · 2.1 Thermochemistry · 3.8 Equilibrium constants · 3.9 Acid-base equilibria
- Question 10 22 marks
Analyse copper in alloys using redox titrations, explain transition metal complex colours and spectra, and use standard electrode potentials and the inert pair effect to predict reactions.
Inorganic Chemistry · Physical Chemistry · 1.3 Chemical calculations · 3.1 Redox and standard electrode potential · 3.2 Redox reactions · 3.3 Chemistry of the p-block · 3.4 Chemistry of the d-block transition metals