An Introduction to Equilibria

Equilibria can be a tricky concept to understand. In order to understand it, you need a good idea of reversible reactions and then a good idea of a dynamic equilibria. So, what is a reversible reaction? Put simply, it is a reaction in which products can be turned into reactants, but reactants can also be turned back into products. This can be shown using the ⇌ symbol: Reactants ⇌ Products For example, ammonium chloride will thermally decompose into ammonia and hydrogen chloride gases, but these gases will ...

Collision theory and mechanisms – linking it together

I’ve just started teaching the kinetics topic to my students and so far we have focussed on the collision theory. Have you heard of this? The collision theory explains to us what happens during chemical reactions in terms of the collision of particles. In order for a chemical reaction to occur, particles need to come together (collide) with sufficient energy (speed). This is called the activation energy (and is defined as the minimum amount of energy required for a chemical reaction). If ...

Four new IB Study Guides Available!

By Wednesday, October 11, 2017 No tags 1

We are pleased to announce the release of four new titles to the OSC IB Study Guide range. Biology Internal Assessment, 3rd ed. SL & HL Ashby Merson-Davies This Guide provides practical support for the Internal Assessment for IBDP Biology, covering all the essential tools and skills, including guidance on statistics. It offers clear insights into interpreting the assessment criteria, using common software, and structuring the write-up. Chemistry Internal Assessment, 1st ed. SL & HL Dave Allen This Guide offers an up-to-date and practical approach to planning, writing, ...

Optical isomerism

Optical isomers are hard to conceptualise. They are molecules with the same molecular formula and structural formula. They look exactly the same both on paper and in the real world. However, they only exist in pairs, it is only possible to get two optical isomers of the same molecule which makes things a bit easier to deal with (it should be notes that a molecule such as C5H12 has three isomers - not optical isomers but structural isomers, namely pentane, 2 methylbutane ...

Gas Volumes

I have written this blog post with all you new first year IB students in mind. If you have started the course recently (or about to start the course very soon) it is likely that the first or second topic that you study will be ‘Stoichiometric relationships’, which is just a posh way of saying ‘moles’. That said, if you are an old hand, a second year IB student don’t stop reading! This blog post contains some important revision for ...

Limiting reagents

Limiting reagents is a concept that is easy to understand in one context... but tricky to understand in another. Before I expand on this statement, what do I mean by limiting reagents? Well, unless you have some super precise mass balances, when carrying out a chemical reaction you will always add too many atoms / molecules / particles of one substance and not enough of the other. The one that you have added too much of is the reagent that is ...

Synthesis of Aspirin

Aspirin has been with us for long time - the first documented reports of its use occurred over 2000 years ago. That said, the aspirin may not be in the form that you instantly think of (ie, a tablet) but it has been used all the same. Aspirin is an analgesic, which means it has pain killing effects and it has been well documented that the ancient Egyptians used a special tea made out of willow bark to treat a number ...

PRE IB: Practical work – good practice

This blog was written by Dave Allen, an experienced IB Chemistry teacher. To read more Chemistry blogs for students and teachers, click here. This is the fourth and final blog post on pre-IB Chemistry. I do hope you have found the mini-series interesting and helpful, hopefully it will have talked you into deciding to follow chemistry at diploma level! This blog post will involve an introduction to lab (practical) work at IB level. You may or may not be aware that your IB ...

PRE IB: The Basics – Bonds

This blog was written by Dave Allen, an experienced IB Chemistry teacher. To read more Chemistry blogs for students and teachers, click here. Knowing your bonds (and structures). This blog post will (hopefully) refresh your memory on bonds and structures that you will need to familiar with in IB Chemistry. Firstly, the bonds When atoms join, we say they ‘bond’ and electrons are the part of the atom that are involved in bonding. There are two types of bond that this blog post will cover: Ionic ...

PRE IB: The Basics – Moles

This blog was written by Dave Allen, an experienced IB Chemistry teacher. To read more Chemistry blogs for students and teachers, click here. Yes, you have read that correctly – we get moles in Chemistry as well as Biology. However, our mole is not the small furry type – it's a number! You see, in Chemistry we count things not the obvious way (i.e., 1, 2, 3, 4, 5 and so on) but by using a word – the ‘mole’ – to represent ...