Entropy Question Practice midterm 2013 5B

[Natalie Yakobian]

Hi,
I am confused with question 5B on the 2013 midterm.
It asks us to put the following substances in increasing order of standard molar entropy
CHF3, CF4, CH3F, CH2F2

I have to conflicting thoughts on this problem.
I understand that heavier molecules have higher molar entropy so CF4 would have the greatest molor entropy,
but if we think about the equation S =klnW, it would seem that CF4 would have the smallest molar entropy because it has only one possible configuration.

Can someone help explain what way we should approach this? Thank you!

[stacey]

CH3F<CH2F2<CHF3<CF4. I think it is because F atom is larger than H atom, thus there are more possible states