Question

The Nernst heat theorem states that the entropy change accompanying any physical or chemical transformation"

A) Is zero
B) Is always positive
C) Approaches zero at absolute zero
D) Depends on the reaction

Answer 1

The Nernst heat theorem, related to the third law of thermodynamics, asserts that entropy change approaches zero at absolute zero. It also reaffirms that the entropy of a substance above absolute zero is positive, aligning with the second law of thermodynamics which maintains that entropy of a system never decreases.

Step-by-step explanation:

The Nernst heat theorem, a part of the third law of thermodynamics, indicates that as the absolute temperature of a substance approaches zero, so does its entropy. More specifically, the entropy change accompanying any physical or chemical transformation approaches zero at absolute zero (Answer C). This conclusion is important because it provides a fixed point of reference, allowing for the calculation of the absolute entropy of any substance at any given temperature. Additionally, it dictates that the sign of entropy of any substance at temperatures above absolute zero is positive, reinforcing the second law which states that the total entropy of a system either increases or remains constant, never decreasing.

During processes, entropy can change in two fundamental ways. For a reversible process, entropy is constant, whereas for an irreversible process, entropy always increases. This increase in entropy is more significant at lower temperatures for a given quantity of heat transfer, Q/T, due to the smaller T value, and thus ensures an overall increase in entropy during such processes.