selects and processes appropriate qualitative and quantitative data and information using a range of appropriate media CH11/12-4

analyses and evaluates primary and secondary data and information CH11/12-5

solves scientific problems using primary and secondary data, critical thinking skills and scientific processes CH11/12-6

communicates scientific understanding using suitable language and terminology for a specific audience or purpose CH11/12-7

explains the characteristics of equilibrium systems, and the factors that affect these systems CH12-12

Static and Dynamic Equilibrium

IQ1: What happens when chemical reactions do not go through to completion?

Students:

● conduct practical investigations to analyse the reversibility of chemical reactions, for example:

– cobalt(II) chloride hydrated and dehydrated

– iron(III) nitrate and potassium thiocyanate

– burning magnesium

– burning steel wool (ACSCH090)

● model static and dynamic equilibrium and analyse the differences between open and closed systems (ACSCH079, ACSCH091)

● analyse examples of non-equilibrium systems in terms of the effect of entropy and enthalpy, for example:

– combustion reactions

– photosynthesis

● investigate the relationship between collision theory and reaction rate in order to analyse chemical equilibrium reactions (ACSCH070, ACSCH094)

Factors that Affect Equilibrium

IQ2: What factors affect equilibrium and how?

Students:

● 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, for example:

– heating cobalt(II) chloride hydrate

– interaction between nitrogen dioxide and dinitrogen tetroxide

– iron(III) thiocyanate and varying concentration of ions (ACSCH095)

● explain the overall observations about equilibrium in terms of the collision theory (ACSCH094)

● examine how activation energy and heat of reaction affect the position of equilibrium

Calculating the Equilibrium Constant (Keq)

IQ3: How can the position of equilibrium be described and what does the equilibrium constant represent?

Students:

● deduce the equilibrium expression (in terms of Keq) for homogeneous reactions occurring in solution (ACSCH079, ACSCH096)

● perform calculations to find the value of Keq and concentrations of substances within an equilibrium system, and use these values to make predictions on the direction in which a reaction may proceed (ACSCH096)

● qualitatively analyse the effect of temperature on the value of Keq (ACSCH093)

● conduct an investigation to determine Keq of a chemical equilibrium system, for example:

– Keq of the iron(III) thiocyanate equilibrium (ACSCH096)

● explore the use of Keq for different types of chemical reactions, including but not limited to:

– dissociation of ionic solutions

– dissociation of acids and bases (ACSCH098, ACSCH099)

Solution Equilibria

IQ4: How does solubility relate to chemical equilibrium?

Students:

● describe and analyse the processes involved in the dissolution of ionic compounds in water

● investigate the use of solubility equilibria by Aboriginal and Torres Strait Islander Peoples when removing toxicity from foods, for example:

– toxins in cycad fruit

● conduct an investigation to determine solubility rules, and predict and analyse the composition of substances when two ionic solutions are mixed, for example:

– potassium chloride and silver nitrate

– potassium iodide and lead nitrate

– sodium sulfate and barium nitrate (ACSCH065)

● derive equilibrium expressions for saturated solutions in terms of Ksp and calculate the solubility of an ionic substance from its Ksp value

● predict the formation of a precipitate given the standard reference values for Ksp