§-Section

Unit 3: Equilibrium, Acids and Redox

19 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

How do we measure and represent the energy change of a reaction?

Define enthalpy change, classify reactions as exothermic or endothermic, and use calorimetry data with energy profile diagrams.

Exothermic and endothermic reactions, enthalpy change, energy profile diagrams, and calorimetry calculations using q = mcdeltaT, with fully worked TASC-style examples.

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Why does iron rust and how do we stop it?

Explain corrosion as an electrochemical process and evaluate methods of prevention.

The electrochemistry of rusting, the roles of oxygen and water, the effect of salt, and prevention methods including barriers, sacrificial anodes and cathodic protection, with worked TASC-style examples.

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How do buffer solutions resist changes in pH?

Explain how a buffer maintains pH using equilibrium and calculate buffer pH.

How a weak acid and its conjugate base resist pH change, the action of buffers when acid or base is added, buffer capacity, and calculating buffer pH with the Henderson-Hasselbalch relationship, with worked TASC-style examples.

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How do reversible reactions reach and respond to disturbances of equilibrium?

Explain dynamic equilibrium, write equilibrium constant expressions, and predict shifts using Le Chatelier's principle.

Dynamic equilibrium, the equilibrium constant Kc, the reaction quotient Q, and using Le Chatelier's principle to predict how concentration, pressure and temperature changes shift a system, with fully worked TASC-style examples.

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How do catalysts speed up reactions without being used up?

Explain how a catalyst increases rate by providing an alternative pathway with lower activation energy.

How catalysts lower activation energy, the difference between homogeneous and heterogeneous catalysts, enzymes, and the effect on the energy profile and Maxwell-Boltzmann distribution, with worked TASC-style examples.

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How do we balance complex redox reactions?

Construct and combine oxidation and reduction half-equations to balance redox reactions.

Writing half-equations, balancing atoms and charge in acidic solution, balancing disproportionation, and combining oxidation and reduction halves into a full ionic equation, with worked TASC-style examples.

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How do we harness electron transfer to produce or use electrical energy?

Describe galvanic and electrolytic cells and calculate cell potentials from standard electrode potentials

Galvanic and electrolytic cells, electrodes and salt bridges, the standard electrode potential table, calculating cell EMF, and predicting spontaneity, with worked TASC-style examples.

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What controls how fast a chemical reaction goes?

Use collision theory to explain how concentration, temperature, surface area and pressure change reaction rate.

Collision theory, activation energy, the Maxwell-Boltzmann distribution, and how concentration, temperature, surface area and pressure change the rate of reaction, with worked TASC-style examples.

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How do we find an enthalpy change we cannot measure directly?

Apply Hess's law and bond enthalpy data to calculate enthalpy changes for reactions.

Hess's law, energy cycles, calculating enthalpy changes from enthalpies of formation, and estimating enthalpy from average bond enthalpies, with fully worked TASC-style examples.

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How do we identify electron transfer and balance redox reactions?

Assign oxidation numbers, identify oxidants and reductants, and balance redox half-equations and overall equations.

Oxidation numbers, the meaning of oxidation and reduction as electron transfer, identifying oxidants and reductants, disproportionation, and balancing redox half-equations and full ionic equations, with worked TASC-style examples.

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How do we relate amounts of reactants and products in a reaction?

Use the mole concept and balanced equations to perform stoichiometric calculations, including limiting reagent and percentage yield.

The mole, molar mass and the Avogadro constant, mole-ratio calculations from balanced equations, limiting reagent, empirical formulae and percentage yield, with fully worked TASC-style numerical examples.

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How do we calculate an unknown concentration from titration data?

Carry out volumetric analysis calculations using moles, concentration and stoichiometry.

Using titration data to find an unknown concentration, the mole-ratio method, standard solutions, dilution, back titration and double (redox) titrations, with fully worked TASC-style examples.

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How do we relate the pressure, volume, temperature and amount of a gas?

Apply the ideal gas equation and molar gas volume to calculate gas quantities in reactions.

The ideal gas equation, the combined gas law, molar gas volume at standard conditions, and using gas data in stoichiometric calculations, with fully worked TASC-style examples.

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How do we measure the strength of a weak acid and find the pH of its solution?

Use Ka and pKa to describe weak acid strength and calculate the pH of a weak acid solution.

The acid dissociation constant Ka and pKa, calculating the pH of a weak acid solution, percentage ionisation, and the relationship between Ka and acid strength, with fully worked TASC-style examples.

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What does a titration curve tell us and how do we choose an indicator?

Interpret titration curves for the four acid-base combinations and select a suitable indicator.

The shape of titration curves for strong and weak acid-base combinations, equivalence point versus end point, the buffer region, half-equivalence pH, and choosing an indicator by its pKa, with worked TASC-style examples.

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How do we describe acid and base strength and calculate the pH of solutions?

Apply the Bronsted-Lowry model, distinguish strong and weak acids, and calculate pH, pOH and Kw relationships.

The Bronsted-Lowry model, conjugate acid-base pairs, strong versus weak acids and bases, the self-ionisation of water, and pH, pOH and Kw calculations with fully worked TASC-style examples.

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How much product does electrolysis make for a given charge?

Apply Faraday's laws to calculate masses and volumes produced in electrolysis.

Quantitative electrolysis using Q = It, the Faraday constant, cells in series, and calculating mass or gas volume from charge passed, with fully worked TASC-style examples.

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How do we quantify the position of an equilibrium?

Write equilibrium expressions and calculate Kc, interpreting its size and units.

Writing the equilibrium constant expression, using an ICE table to calculate Kc from equilibrium concentrations, interpreting its magnitude and units, and the effect of temperature, with fully worked TASC-style examples.

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How do we describe the equilibrium of a sparingly soluble salt?

Write solubility product expressions, calculate Ksp and solubility, and predict precipitation.

The solubility product Ksp, relating Ksp to molar solubility, the common ion effect, and predicting whether a precipitate forms using the ionic product Q, with fully worked TASC-style examples.

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