Question 3 from Quiz 1

[Steven_Liu_3H]

"Which molecule when a single crystal, would you predict to have a larger molar entropy at T=0K: SF6 or SF5CL? Why? (Both molecules have the same geometry with sulfur in the center)".

So according to the third law, should both have the same entropy of S=0 at T=0?

[Theresa Dinh 3F]

They are not perfect crystals, which is the problem. Thus they cannot be exactly S=0.

You have to figure out the entropy using the equation S = K ln W
W is the number of different configurations that a molecule can have.
Since SF6 has only one configuration, but SF5CL can have many different configurations (draw out the lewis diagram), S will be bigger for SF5Cl.