Which of the following best expresses the increased degree of randomness associated with melting and sublimation, respectively?
A) ΔSfus - ΔSsub = 0
B) ΔSfus = 144.3 J/mol-K, ΔSsub = 9.0 J/mol-K
C) ΔSfus = 9.0 J/mol-K, ΔSsub = -144.3 J/mol-K
D) ΔH for both processes is zero
E) ΔSfus = 9.0 J/mol-K, ΔSsub = 144.3 J/mol-K

Question

Quizplus · Accepted Answer

The increased degree of randomness associated with melting and sublimation is expressed by the ΔS value of each process. ΔS represents the change in entropy. Entropy is a measure of the degree of disorder or randomness in a system.

Melting increases the degree of randomness because the solid state has a more ordered arrangement of molecules than the liquid state. Therefore, the ΔS value for melting is expected to be positive.

Sublimation also increases the degree of randomness because the solid state has a more ordered arrangement of molecules than the gaseous state. Therefore, the ΔS value for sublimation is expected to be positive.

The only choice that reflects an increase in randomness associated with both melting and sublimation is E, where ΔSfus is 9.0 J/mol-K, and ΔSsub is 144.3 J/mol-K.

Which of the Following Best Expresses the Increased Degree of Randomness