UTC: Sunday, February 17th, 2019

All creatures great and small and 2016, 6

All things bright & beautiful, all creatures great and small. Remember that hymn? We often talk about remembering the little things, well here’s a lesson in remembering the big things as well! This post started life with an entirely different title. It was initially called, Should I ignore ‘-x’ in my ICE table? I started writing […]

Writing good answers to AP Acid-Base problems

Here’s the latest in the ‘writing good answers’ series, Writing good answers to AP Acid-Base problems. It’s probably the toughest topic on the exam for students, or at least it seems to be, so here are a few pointers that might help when answering questions on acid and bases on the AP chemistry exam. 1. […]

Writing good answers to AP Equilibrium problems

Here’s the latest in the ‘writing good answers’ series, Writing good answers to AP Equilibrium problems. This post only deals with aspects of equilibria such as Kc, Kp, Ksp and Le Châtelier’s Principle – I’ll deal with Acid-Base equilibria in a separate post. So, here’s a list of some pointers to make your AP equilibrium […]

Le Châtelier’s principle in action

Following the mention of the cobalt(II) complex ion system in this post from a couple of days ago, here’s a 30 second video clip of Le Châtelier’s principle in action in the same (with The Smiths). The equilibrium that is set up is this, [Co(H2O)6]2+(aq) + 4Cl–(aq) ⇌ [CoCl4]2-(aq) + 6H2O(l) and the aqueous solution […]

Water in equilibrium mixtures and Le Châtelier’s principle

When it comes to water in equilibrium mixtures and Le Châtelier’s principle, things can be confusing, so let’s try to take some of the mystery out of this. When reading EK6B1a in the AP Chemistry CED, one finds this; The final few words are what I care about here. Where water is important I think […]

Subscriber Update (02-02-16)

Here’s the latest Subscriber Update. In the last few days, the UNIT 5 and UNIT 6 AP NOTES have undergone some tweaking. There have been a few updates in terms of equation rendering to make the aesthetics are little nicer, and in terms of making it clear when ∆G° can be applied, and under what […]

More, potentially useless Wordles

I recently re-visited the Wordles that I first produced in June of 2013 for the original versions of my AP Chemistry notes for Big Ideas 1-6. You can read about them here. Before I update those Wordles again to reflect the newer versions of the notes more than 2 years down the road (which I […]

‘Thermal Energy’ = 2.4 kJ/mol in EK6D1b.??

This post poses a question that I don’t know the answer to. I have asked this particular problem on the College Board’s AP Chemistry electronic discussion group, but so far none of the brightest minds or Test Development Committee members have answered. So, here it is for the ‘internets’ to solve!

‘Expanded LCP’ or ‘Q versus K’ explanations?

It’s never been OK, on the AP exam, to offer a simple, ‘because of Le Châtelier’s principle‘ argument as the explanation for the shift of an equilibrium position caused by an external stress. This is in much the same way that it has never been acceptable to say, ‘because as you go across the period first […]

Inert gases and gaseous equilibrium mixtures

What happens when an inert gas is added to a gaseous equilibrium mixture at constant volume? Before we answer that question, it might be worth defining what we mean by “an inert gas”. In this context we mean a gas that is not involved in the equilibrium reaction, or one that reacts with any of […]