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Module 3: Periodic table and energy (3.2.3 Chemical equilibrium)

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does a reversible reaction reach equilibrium, and how does it respond to changing conditions?

Dynamic equilibrium, Le Chatelier's principle and the effect of concentration, pressure and temperature, the role of a catalyst, the equilibrium constant Kc for homogeneous equilibria, and the compromise conditions used in industry.
An OCR H432 module 3 answer on chemical equilibrium: dynamic equilibrium, Le Chatelier's principle, the equilibrium constant Kc, and the compromise conditions used in industrial processes such as the Haber process.
11 min answer →

How do we measure and calculate the energy released or absorbed in a chemical reaction?

Enthalpy and standard enthalpy changes, exothermic and endothermic reactions, calorimetry and the q = mcDeltaT equation, average bond enthalpies, and Hess's law including formation and combustion cycles.
An OCR H432 module 3 answer on enthalpy changes: standard enthalpy definitions, calorimetry with q = mcDeltaT, bond enthalpy calculations, and Hess's law cycles for formation and combustion.
12 min answer →

How do the trends in reactivity of Group 2 metals and the halogens follow from their electron structures?

Group 2 reactivity and reducing power, reactions of Group 2 elements and their oxides and hydroxides, the halogens as oxidising agents, halide displacement, disproportionation of chlorine, and tests for halide ions.
An OCR H432 module 3 answer on Group 2 and the halogens: reactivity trends, reactions with water and oxygen, halogen displacement, disproportionation of chlorine, and halide ion tests.
11 min answer →

How do the structure of the periodic table and the periodic trends in properties follow from electron configuration?

The periodic table arranged by atomic number into periods and groups, the s, p and d blocks, and the periodic trends in atomic radius, first ionisation energy and melting point across Periods 2 and 3.
An OCR H432 module 3 answer on periodicity: the structure of the periodic table, the s, p and d blocks, and the trends in ionisation energy, atomic radius and melting point across Periods 2 and 3.
11 min answer →

How can simple test-tube reactions identify the ions present in an unknown sample?

Qualitative tests for carbonate, sulfate, halide and ammonium ions, the correct sequence of tests to avoid interference, and the observations and ionic equations for each test.
An OCR H432 module 3 answer on qualitative analysis: tests for carbonate, sulfate, halide and ammonium ions, the order of testing to avoid false results, and the relevant ionic equations.
10 min answer →

What controls how fast a reaction goes, and how does a catalyst speed it up?

Collision theory, the effect of concentration, pressure, surface area and temperature on rate, the Boltzmann distribution and activation energy, and the action of catalysts including the difference between homogeneous and heterogeneous catalysis.
An OCR H432 module 3 answer on reaction rates: collision theory, the effects of concentration, temperature and surface area, the Boltzmann distribution, activation energy, and catalysis.
11 min answer →