Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: digisol on February 04, 2020, 11:05:51 AM

I am helping someone study for a CLEP test using a book of practice problems with answers. I'm struggling to understand the answer given for this problem:
Which is NOT true for entropy in a closed system according to the equation Δ S=Q/T?
A. Entropy is a measure of energy dispersal in the system
B. Equation is only valid for a reversible process
C. Changes due to heat transfer are greater at low temperatures
D. Disorder of a system decreases as heat is transferred out of the system
E. Increases as temperature decreases
They give the answer as C, with this explanation:
The equation relates to the change in entropy ( Δ S) at different temperatures. Entropy increases at higher temperatures (i.e. increased kinetic energy).
To me, it seems like C and E say the same thing, and that both are true, hence neither would be the correct answer. A, B, and D also seem to be true, so there would be no correct answer given among the choices. Am I missing something?

C and E certainly do not say the same thing. E is talking about entropy, C is talking about entropy CHANGE. This is a VERY important distinction (for other quantities too, not just entropy) which you must clearly grasp to get anywhere in thermodynamics.
Entropy increases at higher temperatures, so E is wrong.
Entropy CHANGE due to heat transfer, by the equation ΔS = Q/T, is greater at lower temperatures for a given Q. So C is true.