Equilibria part 2

Last month I ran over the basics of equilibria. The rationale for this was that I felt that it was a part of the course that had been poorly answered in the recent IB May examinations. I do need to stress that this is my own personal opinion and not that of the IB. This month I will run over the more difficult concepts associated with equilibrium, Le Chatelier’s principle. Le Chateliers principle allows you to determine what happens to a system ...

Forwards, backwards, left or right? – Equilibria Part 1

There were a few questions on equilibria in this year’s May exams. As a teacher I felt that students didn’t perform very well on these questions (I have no evidence for this apart from conversations with a very small number of students who sat the exams) so thought that this month may be an opportunity to help reinforce and summarise some of the concepts covered. First of all, what do we mean by equilibrium? A reaction that is at equilibrium doesn’t ...

Get it right – Electrochemical Cells

This aim if this blog post is to equip you with an aid memoir – something you can copy, paste, edit and print out to aid your revision. The reasoning behind this post is from my experience as an examiner. In my opinion (and this may not be one shared by the IB) students tend to answer questions on electrochemical cells quite poorly. This is possibly due to the topic being one of the last topics to be taught – maybe ...

Caffeine

We all love our caffeine hit in the morning, but what is this magic ‘energy’ giving substance and is it actually good for us? The IUPAC name for caffeine is 1,3,7-Trimethylpurine-2,6-dione and the molecule has the following structure: By Vaccinationist - Own work, based on PubChem, Public Domain, https://commons.wikimedia.org/w/index.php?curid=54417143 Interestingly, you may notice that the structure is similar to adenosine and guanine (DNA purine bases) – the clue comes from the name. Caffeine is a psychoactive drug, which puts it in the same group ...

Sigma, Pi, Hybridization and Shape

Sigma bonds, Pi bonds. Shapes of molecules. Hybrid orbitals. How do they all fit together? I was really confused with this information when I was a student. It wasn’t covered when I did my biochemistry degree and I only felt like I really understood things until I started teaching about the concepts … so I really hope this blog post helps your understanding of things. Where do I start? Well, the three above concepts (Sigma & Pi, shape and hybrid orbitals) are, in my ...

End Game

If you are an IB2 student who sits their exams in the May exam session, as the month of March, it comes to an end your thoughts are probably on revision. If your teachers have yet to finish the course, they will probably be almost there. If they haven’t yet finished, don’t let this from stopping you from carrying out some revision! If you didn’t know it, the IB Chemistry exam this year is on Wednesday 22nd May (Papers 1 ...

The Biochemistry Option

Proteins Proteins are a group of biomolecules (or biopolymers) that form enzymes and muscles in the body. They are the chief nitrogenous compounds found in living organisms but are still only approximately 15% nitrogen. The other elements they are comprised of is carbon, oxygen, hydrogen and a relatively small amount of sulphur. Proteins are made of amino acids which, as the name implies, are made from amino groups (NH2) and carboxylic acid groups (COOH). These groups are joined together via a carbon ...

Formaldehyde

Formaldehyde was recently in the news … But more of this later. To start with, you may be asking, what is formaldehyde? Formaldehyde is the non-UPAC name for methanal, CH2O, the simplest of all aldehydes. At room temperature, it is found as a gas (boiling point -19oC). It does have a dipole moment but due to its low Mr (and hence weak London dispersion forces), it has a low boiling point. It is found in the atmosphere and also in space. Due to ...

Ethanedioic Acid Titrations

It's that time of year where if you are in IB1 you may well be starting to think about your IA. What will you do?! I hope today's post gives you some ideas. Have you thought about working with Ethanedioic acid (HOOCCOOH) or oxalic acid to give you its more common name? Ethanedioic acid occurs as a free acid in beetroot leaves and rhubarb. Could you extract it and see how much you have? You could titrate it with a base, such ...

SN1 vs SN2

I have not long been back from Oxford in the UK where I was running a revision course for OSC. One of the concepts that the students seemed needing clarifying was when to decide when an organic reaction was SN1 or SN2 so I thought it may be worth sharing this with you in this blog post: First of all, some definitions. S = Substitution (there are other types of mechanisms out there such as elimination and addition.) N = Nucleophilic (it is ...