Why All Equilibrium Constants Are Actually the Same | MCAT Content 

Thank you. I am working on more videos and should be more consistent going forward.

Thank you glad the videos are helpful.

If the question is just asking about solubility (which is what I would expect of an AAMC question) then you should still rank them by Ksp values. However, if they are asking about how much of a particular component would end up in solution they would have to specify what exactly you are measuring (there is an example of this in the AAMC Chemistry question pack it’s number 98.) In this case I suspect they would still keep the number of ions of whatever they want you to measure the same across the different compounds. If they didn’t do that this question would essentially turn into an equilibrium question (ICE table territory) where you would have to solve for the amount of that specific ion that dissolves into solution. I highly doubt the AAMC would do this because it would be fairly time consuming and from what I have seen equilibrium style question only usually require you to calculate something once. Did you have a specific example problem in mind? There might be something I am missing but if I saw the a specific question I could probably figure out how they wanted you to solve it.

If you ever need to solve for that concentration value then you will plug in a 2x if something has stoichiometric coefficient of 2. So in the example if you wanted to solve for the [Cl] in solution you would plug in 2x into the equation we have set up and square it. Does that make sense?

The website is definitely a work in progress sorry about that. I am currently working on a course but I don't have a full one that you can purchase. However, I do offer subscription based "office hours" and will of course continue to post more free videos here. If you want more information about office hours feel free to send me an email at chriscernac@eightfoldlearning.com

@@EightfoldMCAT Thank you for the information. I will reach out to you!

While all of the K values are all equivalent to [products]/[reactants] the different values do describe different equilibriums. For example, Ksp deals with solubility so the higher the Ksp the more soluble that compound, but Ka on the other hand describes the acid dissociation or how much an acid breaks into hydrogen ions plus its conjugate base. So the higher the Ka value the more that acid will dissociate into hydrogen ions which is why stronger acids have larger Ka values since they dissociate more easily into hydrogen ions. While Kd in the case of enzyme kinetics describes dissociation so the larger the Kd value the more dissociated a molecule is from whatever it binds to. This is why we say that enzymes with high Kd (high dissociation) have low affinity for their substrate molecules. The trick with the K value is just realizing that the larger the number the more of whatever they stand for.

The higher the Ka the higher the association (aka affinity). Low Km values refer to enzymes with high affinities so those two values go together. While high Kd value means high dissociation. If you are really dissociated then you must not have high affinity for what you are supposed to be binding. This lines up with high Km values and in some ways you can see Kd and Km as measuring the same thing. They aren’t 100% analogous, but for the MCAT you can treat them as though they are.

@@EightfoldMCAT Wonderful THANK YOU !!!