BlogChemistryThe Ultimate Guide to QCAA Chemistry Unit 3: Equilibrium, Acids and Redox Reactions
The Ultimate Guide to QCAA Chemistry Unit 3: Equilibrium, Acids and Redox Reactions
Have you started studying Unit 3 of QCAA Chemistry in class but are a little confused about what you’re meant to be learning? No worries, we’re here to help!
To make things easier for you, we’ve broken down what you’ll be learning in each of the topics for Unit 3 of QCAA Chemistry and what assessments you’ll be completing.
Unit 3 is the first of your two formative senior units for QCAA Chemistry. This means that the assessments you complete for this unit will count towards your ATAR.
The unit is split into two topics: chemical equilibrium systems, and oxidation and reduction, which cover a variety of subtopics from equilibrium constants to electrolytic cells.
We’ll break down each of these topics so you know exactly what you’ll be studying!
Topic 1: Chemical Equilibrium Systems
Chemical Equilibrium
This subtopic covers:
open VS closed chemical systems
forwards VS reverse reactions
reversibility/irreversibility of physical VS chemical changes
what it means for a system to have reached a dynamic equilibrium
observable chemical and physical changes of a chemical system and what they mean at an atomic and molecular level
When studying this area, it may be helpful to revise the following topics:
Unit 1 Topic 3: Chemical reactions: reactants, products and energy change
Unit 2 Topic 3: Rates of chemical reactions
Factors that Affect Equilibrium
This subtopic covers:
the effect that increasing or decreasing temperature, pressure or concentration can have on a particular chemical system at equilibrium
understanding and applying Le Châtelier’s principle
Equilibrium Constants
This subtopic covers:
understanding that the equilibrium constant (KC) is a ratio of the product and reactant concentrations at equilibrium
understanding how to apply the KC formula
Relevant Formulas
Properties of Acids and Bases
This subtopic covers:
understanding that acids dissociate to produce H+ ions
understanding that bases dissociate to produce OH– ions
understanding that redox reactions involve oxidation of one substance and reduction of another substance
types of redox reactions e.g. combustion, displacement of metals, corrosion
understanding how an atom’s position in the periodic table relates to its ability to gain or lose electrons
identify oxidised and reduced species in redox reactions
applying Oxidation Number Rules to deduce oxidation states of atoms in an ion or compound
Electrochemical Cells
This subtopic covers:
understanding that electrochemical cells consist of oxidation and reduction half-reactions connected via an external circuit that allows electrons to move from the anode (oxidation reaction) to the cathode (reduction reaction)
understanding that galvanic cells generate an electrical potential difference from a spontaneous redox reaction
understanding that oxidation occurs at the negative electrode (anode) and reduction occurs at the positive electrode (cathode)
describing and labelling the components of a galvanic cell on a diagram, including: the oxidation and reduction half-cells, the positive and negative electrodes and their solutions of their ions, the flow of electrons, the movement of ions and the salt bridge
Things to Remember
anode is negative (-)
cathode is positive (+)
spontaneous reaction occurs
does not require external energy source
converts chemical energy into electrical energy
EMF is positive (+)
Image sourced from Oxford Chemistry Units 3 & 4
Standard Electrode Potential
This subtopic covers:
understanding that the standard electrode potential is the electrical potential than an electrode generates under standard conditions
determining the relative strength of oxidising and reducing agents by comparing standard electrode potentials
understanding that the limit of standard electrode potentials is that they can only be applied to aqueous equilibrium
using appropriate formulas and convention to complete relevant calculations
understanding that electrolytic cells use an external electrical potential difference to provide the energy to allow a non-spontaneous redox reaction to occur
predicting and explaining the products of the electrolysis of a molten salt and aqueous solutions of sodium chloride and copper sulfate
describing and labelling the components of a galvanic cell on a diagram, including source of electric current and conductors, positive and negative electrodes and the electrolyte
Things to Remember
cathode is negative (-)
anode is positive (+)
non-spontaneous reaction occurs
requires external voltage source
converts electrical energy into chemical energy
EMF is negative (-)
Image sourced from Oxford Chemistry Units 3 & 4
QCAA Chemistry Unit 3 Assessments
Want to know the marks you need to achieve to score your ATAR goal? Check out our QCE Cohort Comparison Tool!
It is an exam that consists of both Unit 3 and 4 content and constitutes 50% of your overall grade. To find out how to best prepare for the external assessment, see How to Ace Your External Assessment for QCAA Chemistry.
#1: Create a revision table like the one below using the syllabus dot points to guide you
#2: Get visual!
Use diagrams, flowcharts and other visual forms of displaying information where you can when making your notes.
#3: Don’t forget examples
Include examples of each concept you learn about. For example, when learning about buffer solutions, make sure to include examples of a few relevant buffer solutions.
#4: Manage your time well
The syllabus has a guide to how much time should be spent on each subtopic. Although this guide is technically for teachers and their lesson planning, you as a student can also use it to help guide your study (i.e. to figure out what topics may be more important and therefore require more study time)
Are you looking for some extra help with revising QCAA Chemistry Unit 3?
We have an incredible team of QLD Chemistry tutors and mentors!
We can help you master the QCAA Chemistry syllabus and ace your upcoming Chemistry assessments with personalised lessons conducted one-on-one in your home or online!
We’ve supported over 8,000 students over the last 11 years, and on average our students score mark improvements of over 20%!
To find out more and get started with an inspirational QLD tutor and mentor,get in touch today or give us a ring on 1300 267 888!
Yalindi Binduhewa is an Art of Smart tutor based in Queensland and was part of the very first cohort to go through the ATAR system, so she knows exactly how fun and enjoyable it can be. She is currently studying a Bachelor of Medical Imaging (Honours) at QUT and is loving it. When she’s not doing uni-related stuff or tutoring, she’s hanging out with her friends, rewatching a show for the 100th time, or trying out new crafty projects and discovering that she doesn’t have a talent for everything.
