10 posts • Page 1 of 1
From my understanding, activity is a way to compensate the differences between ideal vs. real behavior in molecules. Real reactions don't occur as idealized due to the additional molecular interactions that occur outside of the specific reaction, so the real pressure/concentration doesn't match exactly with the idealized one. Activity takes into account intermolecular interactions that occur with the particular molecule, while molar concentration doesn't. When dealing with low concentrations, this difference doesn't matter since there's a lower number of molecules in proportion to the environment, so less interactions occur. But when there's a higher concentration, more intermolecular reactions occur outside of that "main" reaction, so the idealized value of K differs from the actual value. For finding the equilibrium constant, the difference between the activity and the concentration/partialpressure is small enough that it doesn't matter, which is why activity isn't used for this. (I might be wrong, and if I am please correct me)
I had this same question too! I take it as meaning a species in a K expression. I don't think it really matters whether or not we know the actual thermodynamical definition because the textbook says that we learn more in-depth about it in a more advanced course. And, I haven't seen Dr. Lavelle use it.
This was a bit confusing to me too but I think Dr. Lavelle mentions it briefly in one of the Audio/Visual Videos. I think it has to do with the measure of the substance being used in the K expression. So when we have the concentrations in the K ratio: [P]/[R], this can also be expressed as [activity of P]/[activity of R].
Who is online
Users browsing this forum: No registered users and 3 guests