Hi,
"I was working on this question but I was not able to understand why the answer is B and not C. I thought that increased stability indicated Thermodynamic control while decreased stability indicated Kinetic control (this reasoning would lead me to choose answer C). The question requires passage information so it is not really easy to post the question and answers out of context. Would someone please clarify where my reasoning is going wrong?"
Yes, thermodynamic control involves getting to the most stable products, and kinetic control involves making the product that has the lowest activation barrier to get here.
In this question, the implication is that the complete mixing of liposomes done by compound 2 is the thermodynamic product.
The two types of situation we are comparing for this type of liposomal mixture based on the passage are:
Situation 1. The two different size of liposomes stay as big (B) and small (b) liposomes, and you just wind up with a mixture of B and b. This is what happens for compound 1 liposomes.
Situation 2. The two different size liposomes recombine to form average size (M) liposomes, and you wind up with a solution of just M. This is what happens for compound 2 liposomes.
To figure out which is under thermodynamic control, we need to determine what is the most thermodynamically stable state.
If we use the formula dG = dH - TdS conceptually, we realize that an equilibrium wants to maximize bonds formed and the disorder in a system, which is also known as the number of microstates available to the system.
If we consider the dH component, it is largely the same for both case 1 and case 2, because regardless of liposome size b B or M, all compounds inside the liposome are roughly bonded in the same way, where one molecule is surrounded by others.
What is more significant is the dS component of the liposomal mixtures. There are more equal energy ways to arrange a solution full of only M particles than a mixture of b and B particles.
This means that situation 2 has a greater degree of disorder, and is therefore more thermodynamically stable. Because compound 2 achieves the most stable thermodynamic state 2, compound 2 is under thermodynamic control. Because compound 1 is observed to be trapped in situation 1, it is under kinetic control.
This is a pretty complicated application of thermodynamic vs kinetic control. If you even got to the point of B vs C you're doing pretty well because then you have a 50/50 shot at it.
Hope this helps!
Katt