WJEC A Level Chemistry
WJEC A Level Chemistry Unit 3: Physical and Inorganic Chemistry Exam Questions
Free WJEC A Level Chemistry exam questions for Unit 3: Physical and Inorganic Chemistry, with a mark scheme for every pack. Covers electrode potentials, redox titrations, p-block chemistry, transition metals, kinetics, lattice and hydration enthalpies, entropy, Kc and Kp, pH and buffers.
Unit 3: Physical and Inorganic Chemistry exam questions
9 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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A-Level Chemistry Flashcards for 2027 Onwards
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About WJEC A Level Chemistry Unit 3: Physical and Inorganic Chemistry
Unit 3 is an A2 unit of the WJEC A Level Chemistry course covering the physical and inorganic chemistry of the second year. It includes standard electrode potentials and redox reactions, p-block chemistry (Groups 3 to 7), the d-block transition metals, chemical kinetics, enthalpy changes for solids and solutions, entropy and feasibility, equilibrium constants and acid-base equilibria. It extends the AS work of Units 1 and 2 on bonding, energetics, rates and equilibria. Examiners expect fluent calculations of pH, Kc, Kp, E cell, delta G and rate constants, and clear explanations of inorganic observations such as colour changes and precipitates.
What you need to know
- 3.1 and 3.2 Redox Standard electrode potentials, the standard hydrogen electrode and E cell calculations to predict feasibility. Redox titrations with potassium manganate(VII) and iodine-thiosulfate.
- 3.3 p-block Electron deficiency in Group 3 compounds and dimer formation (Al2Cl6); inert pair effect in Groups 4 and 5; oxides and chlorides of Group 4; reactions of halogens and halides including with concentrated sulfuric acid.
- 3.4 d-block transition metals Electronic configurations, variable oxidation states, complex ions and shapes, colour from d orbital splitting, ligand exchange, reactions of aqueous ions with NaOH, and catalytic properties.
- 3.5 Chemical kinetics Rate equations, orders from experimental data, rate constants and units, half-life, rate-determining step and the Arrhenius equation.
- 3.6 and 3.7 Energetics and entropy Born-Haber cycles, lattice and hydration enthalpies, enthalpy of solution, entropy changes and Gibbs free energy, delta G = delta H - T delta S.
- 3.8 and 3.9 Equilibria Kc and Kp, effect of temperature on K; Kw, Ka, pKa, pH of weak acids and strong bases, buffers, titration curves and indicators.
Common mistakes in Unit 3: Physical and Inorganic Chemistry
- Forgetting to square [H+] when using Ka for a weak acid, or using the strong acid method for a weak acid.
- Writing E cell as E(oxidation) minus E(reduction), giving the wrong sign.
- Describing colour as the light absorbed. The observed colour is the complementary colour transmitted.
- Getting the units of the rate constant wrong. Derive them by rearranging the rate equation.
- Using T in Celsius in delta G or Arrhenius calculations.
Try three Unit 3: Physical and Inorganic Chemistry exam-style questions
1. Calculate the pH of 0.0500 mol dm-3 propanoic acid. Ka = 1.35 x 10^-5 mol dm-3. (3 marks)
Show the mark scheme answer
[H+]^2 = 1.35 x 10^-5 x 0.0500 = 6.75 x 10^-7; [H+] = 8.22 x 10^-4 mol dm-3; pH = 3.09.
2. For a reaction delta H = -92 kJ mol-1 and delta S = -199 J K-1 mol-1. Calculate delta G at 298 K and state whether the reaction is feasible. (3 marks)
Show the mark scheme answer
Delta G = -92 - 298 x (-0.199); = -92 + 59.3 = -32.7 kJ mol-1; negative so feasible at 298 K.
3. Describe what is seen when sodium hydroxide solution is added to separate solutions of iron(II) and iron(III) ions. (2 marks)
Show the mark scheme answer
Iron(II): green precipitate (which darkens to brown on standing in air); iron(III): orange-brown (rust coloured) precipitate.
Unit 3: Physical and Inorganic Chemistry FAQs
What does WJEC A Level Chemistry Unit 3 cover?
It covers redox and electrode potentials, p-block chemistry, transition metals, kinetics, lattice and solution enthalpies, entropy and Gibbs energy, equilibrium constants and acid-base equilibria.
How do I revise Unit 3?
Keep a formula sheet of every equation (pH, Ka, Kc, Kp, E cell, delta G, Arrhenius), practise calculations weekly and learn a table of inorganic observations with colours.
Which calculations come up in Unit 3?
Expect pH of strong and weak acids, strong bases and buffers, Kc and Kp, E cell, Born-Haber, delta G and the temperature at which a reaction becomes feasible, rate constants and redox titrations.
