§-Module

Module 5: Equilibrium and Acid Reactions

10 dot points across 5 inquiry questions, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

Inquiry Question 1: What happens when chemical reactions do not go through to completion?

Explore the relationship between entropy, enthalpy and Gibbs free energy in the context of a reaction's spontaneity, and evaluate given the equation delta-G = delta-H minus T delta-S why a reaction that has a negative delta-H is not always spontaneous, and why some reactions do not go to completion

Entropy, enthalpy and Gibbs free energy. What entropy and enthalpy each measure, why delta-G = delta-H minus T delta-S decides spontaneity, why an exothermic reaction can still be non-spontaneous, and why most reactions stop at equilibrium rather than completion.

10 min read →

Investigate the differences between static and dynamic equilibrium, and reversible and non-reversible reactions, using practical examples

Static and dynamic equilibrium. The definitions, the macroscopic vs molecular view, classic practical examples (NO2/N2O4, cobalt complexes, sealed water), and the worked HSC past exam questions.

8 min read →

Inquiry Question 2: What factors affect equilibrium and how?

Use collision theory to explain and predict the effect of concentration, temperature, surface area and catalysts on the rate at which a system approaches equilibrium

Collision theory. How concentration, temperature, surface area and catalysts change reaction rate by changing collision frequency and the fraction of successful collisions, the Maxwell-Boltzmann link to activation energy, and why a faster approach to equilibrium does not change its final position.

10 min read →

Investigate the effects of temperature, concentration, volume and/or pressure on a system at equilibrium and explain how Le Chatelier's principle can be used to predict such effects

Le Chatelier's principle. How concentration, pressure, volume and temperature shift equilibrium position, the role of catalysts, the Haber process worked example, and the past HSC questions markers reward.

9 min read →

Inquiry Question 3: How can the position of equilibrium be described and what does the equilibrium constant represent?

Deduce the equilibrium expression (in terms of Keq) for homogeneous reactions, and perform calculations to find the value of Keq and concentrations of substances within an equilibrium system

Equilibrium constant. Deriving the Keq expression, interpreting its magnitude, the ICE table method, and worked HSC calculations for finding Keq and equilibrium concentrations.

9 min read →

Inquiry Question 4: How does solubility relate to chemical equilibrium and the position of equilibrium?

Predict the solubility of an ionic substance by applying solubility equilibrium principles, and perform calculations involving the solubility product constant (Ksp) and the ionic product

Solubility product. Writing Ksp expressions, predicting precipitation using the ionic product Q vs Ksp, the common ion effect, and worked HSC calculations for solubility and precipitation.

9 min read →

Inquiry Question 5: How are acids and bases defined and how do they behave in aqueous solution?

Investigate the Brønsted-Lowry theory of acids and bases, including conjugate acid/base pairs and the behaviour of amphiprotic species

Brønsted-Lowry acid-base theory. Definitions, conjugate acid-base pairs, amphiprotic species (water and bicarbonate), how the theory extends Arrhenius, and the worked HSC past exam questions.

8 min read →

Investigate the structure and properties of buffer systems, including their composition, how they resist pH change, and their importance in natural systems such as blood

Buffer systems. The composition of a buffer (weak acid plus conjugate base), how the equilibrium resists pH change, the Henderson-Hasselbalch equation, the carbonic acid blood buffer, and worked HSC past exam questions.

9 min read →

Conduct an investigation to perform titrations of strong acid and strong base, weak acid and strong base, and weak base and strong acid, and analyse the data to determine concentration, pH at the equivalence point, and appropriate indicator selection

Titrations. The four titration curve shapes, equivalence vs end point, indicator selection rules, calculating unknown concentrations from titration data, and worked HSC past exam questions.

9 min read →

Conduct investigations and perform calculations to determine the pH and pOH of strong and weak acids and bases, applying the formulae pH equals negative log of hydrogen ion concentration, and pH plus pOH equals 14

PH and pOH. The pH and pOH formulae, the auto-ionisation of water, strong vs weak acid/base calculations using ICE tables, dilution effects, and worked HSC past exam questions.

9 min read →