IB Chemistry Oxidation & Reduction review & tips
When studying for your IB exams, you’ll need to do a thorough review of the parts of the syllabus you find challenging. If you’re an IB Chemistry student who is a bit confused about Oxidation and Reduction, then this quick article is for you. It’s an excerpt from our Chemistry SL study guide written by Cameron Lumsden, but is relevant to both HL and SL Chemistry students. Read on for a clear explanation of Oxidation and Reduction as well as helpful tips, including an easy to remember mneumonic device. You can find a comprehensive review of the syllabus IB Chemistry syllabus along with exam tips, easy-to-replicate diagrams, and revision advice in our IB Chemistry study guides available in our store.
Oxidation and Reduction
Oxidation and Reduction - “Redox” to chemists - reactions are those that involve a transfer of electrons. Don’t all reactions involve a transfer of elements? - NO! Acid/Base reactions and precipitation reactions do not involve a transfer of electrons.
In IB Chemistry, we are mostly concerned with the electronic definition of oxidation and reduction. The oxygen and hydrogen are included as additional information.
My favourite way to remember this is “AN OIL RIG CAT”. ANode is the electrode where Oxidation Is Loss of electrons occurs, and Reduction Is Gain of electrons at the CAThode.
Oxidation Numbers
Oxidation numbers are chemists’ way to keep an account of electrons.
Remeber to be organised in your working for determining oxidation numbers.
It’s the bottom numbers that have to add to zero (or the overall ionic charge).
Redox Reactions
A redox reaction is one that has changes in oxidation number. There are lots of reactions which are not redox reactions - precipitations, acid/base reactions etc.
Reactions that are always going to be redox reactions:
Combustion reactions - elemental oxygen becoming a compound.
Synthesis reactions - any element reacting with another to produce a compound.
Ions changing charge -
Ions of the oxy-acids changing the number of oxygen atoms -
A fast way to pick off 99% of redox reactions is to look for an element as a reactant or product. This works because the oxidation state of any free element is zero, and in a compound, it is unlikely zero.
Oxidizing agent - a species that removes electrons from another.
Reducing agent - a species that donates electrons to another.
Common Oxidizing & Reducing Agents
Continue your IB Chemistry revision
You’re on your way to filling your knowledge gaps in IB Chemistry. Don’t stop now. What other areas of the syllabus do you find challenging? How are you planning to address your knowledge gaps before your IB exams? If you’re looking for a resource that can provide you with comprehensive, easy-to-follow explanations of sllyabus topics as well as lots of practice questions to test your understanding then pick-up a copy of either our Chemistry SL or Chemistry HL study guide. You can also find more quick-read resources on our IB Chemistry subject page.
