Coaching Centre
Chapter 6: Acid/Base Reactions Notes
HSC Chemistry Module 6: properties, naming and reactions of acids and bases, indicators, enthalpy of neutralisation, how the Arrhenius and Brønsted–Lowry models developed, conjugate pairs and amphiprotic species, pH, pOH, Kw, Ka and pKa, strong versus weak and concentrated versus dilute, titrations and titration curves, conductometric titrations, back titrations and buffers.
Sections
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6A Properties and reactions of acids and bases Mastered
Properties and IUPAC names of common inorganic acids and bases, amphoteric oxides, and balanced, ionic and net ionic equations for acids reacting with bases, carbonates and metals, plus everyday and industrial uses of neutralisation.
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6B Acid–base indicators Mastered
How indicators work as weak acids whose two forms have different colours, colour change ranges and pKa, universal indicator, natural indicators from plants, and the practical investigation to prepare an indicator and use it to follow the pH during a reaction.
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6C Enthalpy of neutralisation Mastered
The molar enthalpy of neutralisation, why strong acid–strong base values are all about −57 kJ/mol and weak ones are smaller, and the practical investigation to measure it with a polystyrene-cup calorimeter, including temperature–time extrapolation, calculations and sources of error.
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6D Changing models of acids and bases Mastered
How the definition of an acid changed from Lavoisier's oxygen theory to Davy's replaceable hydrogen, Arrhenius's ions in water and the Brønsted–Lowry proton-transfer model, with the evidence that overturned each one and the limitations of each model, plus the Lewis model as an extension.
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6E Conjugate pairs and amphiprotic species Mastered
Using the Brønsted–Lowry model to identify conjugate acid–base pairs, write ionisation equations for acids and bases in water (including polyprotic acids), explain the amphiprotic behaviour of water, hydrogen carbonate and dihydrogen phosphate, predict which way a proton transfer goes, and explain why some salts are acidic or basic.
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6F pH, pOH and the ionisation of water Mastered
The self-ionisation of water and Kw, how Kw and neutral pH change with temperature, calculating pH, pOH, [H₃O⁺] and [OH⁻] for strong acids and bases, significant figures in pH, and the pH of solutions after dilution or mixing, with a practical to measure the pH of a range of acids and bases.
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6G Strong and weak acids, Ka and pKa Mastered
Strength versus concentration, strong and weak acids as an equilibrium between molecules and ions, the acid dissociation constant Ka and pKa, percentage ionisation, calculating the pH of weak acids with ICE tables and the 5% rule, finding Ka from a measured pH, and Kb for weak bases.
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6H Standard solutions and titration Mastered
Volumetric analysis: standard solutions and the properties of primary standards, preparing a standard solution, standardising sodium hydroxide, titration glassware and how to rinse it, reading a burette, concordant titres, titration calculations including dilution steps, and the errors that affect results.
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6I Titration curves and conductivity graphs Mastered
Reading pH titration curves for strong and weak acids and bases: initial pH, buffer region, half-equivalence point where pH = pKa, equivalence point pH and the steep jump; choosing an indicator; polyprotic curves such as sodium carbonate; and conductometric titrations, why their graphs have the shapes they do and when to use them.
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6J Back titrations and chemical analysis Mastered
Why and how back titrations are used, with step-by-step calculations for limestone, antacids, ammonium fertilisers and aspirin; analysing a household substance; and evaluating the role of acid–base titration in industry, quality control and research, including Australian examples and First Nations knowledge behind a modern drug.
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6K Buffers Mastered
What a buffer is, how a weak acid and its conjugate base resist changes in pH (with equations and Le Chatelier's principle), preparing a buffer, buffer capacity and range, the Henderson–Hasselbalch equation as an extension, and natural buffers in blood, cells and the ocean, including ocean acidification and the Great Barrier Reef.
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6L Acid/base reactions review Mastered
A summary of Module 6 Acid/Base Reactions, how the ideas connect, the key formulas and words, and a mixed HSC-style test covering acid reactions, indicators, enthalpy of neutralisation, models of acids, pH and Ka calculations, titrations and buffers.