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Unit 3: Physical and Inorganic Chemistry

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do we measure acidity and control pH?

pH, Ka and pKa, strong and weak acids and bases, the ionic product of water, buffer solutions and pH titration curves.
A focused answer to WJEC A-Level Chemistry Unit 3, covering pH and the ionic product of water, Ka and pKa for weak acids, strong and weak acid and base calculations, buffer solutions and pH titration curves.
12 min answer →

How do we express rate mathematically and deduce a mechanism?

Rate equations, orders of reaction, the rate constant, half-life, determining orders from data, the rate-determining step and the Arrhenius equation.
A focused answer to WJEC A-Level Chemistry Unit 3, covering rate equations and orders of reaction, the rate constant and its units, half-life, determining orders from initial-rate data, the rate-determining step and the Arrhenius equation.
12 min answer →

What makes the transition metals special?

Transition metal characteristics, variable oxidation states, complex ions and ligands, coloured ions, catalysis, and ligand substitution.
A focused answer to WJEC A-Level Chemistry Unit 3, covering transition metal characteristics, variable oxidation states, complex ions and ligands, the origin of colour, catalysis, and ligand-substitution reactions.
12 min answer →

How do properties vary across and down the p-block?

Trends in Group 3 to Group 7, the inert pair effect, oxides and chlorides of Period 3, oxidising and reducing behaviour, and tests for ions.
A focused answer to WJEC A-Level Chemistry Unit 3, covering trends across and down the p-block, the inert pair effect, the oxides and chlorides of Period 3, oxidising and reducing behaviour, and qualitative tests for anions.
12 min answer →

What makes a reaction feasible?

Born-Haber cycles and lattice enthalpy, enthalpy of solution, entropy, and Gibbs free energy as the criterion for feasibility.
A focused answer to WJEC A-Level Chemistry Unit 3, covering Born-Haber cycles and lattice enthalpy, enthalpy of solution, entropy changes, and Gibbs free energy as the criterion for reaction feasibility.
12 min answer →

How do we quantify the position of an equilibrium?

The equilibrium constants Kc and Kp, writing and evaluating expressions, units, the effect of changing conditions, and the role of a catalyst.
A focused answer to WJEC A-Level Chemistry Unit 3, covering the equilibrium constants Kc and Kp, writing expressions and determining units, calculating values from equilibrium amounts, and how temperature, pressure and catalysts affect them.
12 min answer →

How do electrode potentials predict redox behaviour?

Standard electrode potentials, the standard hydrogen electrode, electrochemical cells, calculating cell EMF, and predicting the feasibility of redox reactions.
A focused answer to WJEC A-Level Chemistry Unit 3, covering standard electrode potentials and the standard hydrogen electrode, electrochemical cells, calculating cell EMF, and using electrode potentials to predict whether a redox reaction is feasible.
12 min answer →

How do we track and balance electron transfer?

Oxidation and reduction in terms of electron transfer and oxidation number, oxidising and reducing agents, redox half equations, and redox titrations.
A focused answer to WJEC A-Level Chemistry Unit 3, covering oxidation and reduction as electron transfer and changes in oxidation number, oxidising and reducing agents, constructing redox half equations, and redox titration calculations.
12 min answer →