Question

What is the entropy of an ideal crystal at absolute zero, according to the 3rd law of thermodynamics?

• A. There is no way to know.
• B. Infinity
• C. 1
• D. \N

Answer 1

The correct option is D \N

According to the Third Law of thermodynamics, an ideal crystal has zero entropy at Zero Kelvin (absolute zero).

Theory:

Third law of thermodynamics : Entropy of pure and perfectly crystalline substance at $0K$ is zero. A perfect crystal is a crystal that contains no point, line, or planar defects. There are a wide variety of crystallographic defects. Kinetic energy is directly proportional to Temperature, when temperature becomes zero then kinetic energy will also be zero. Pure corresponds to no mixing of foriegn substances. For perfectly crystalline substance entropy $S=0$ at $0K$
Residual entropy : Entropy possessed by a certain substance at $0K$ . Residual entropy is because of the arrangement of the particles.
Important points regarding Third law of thermodynamics :
From a thermodynamic point of view, we have chosen the value zero as per our convenience.
However, the molecular interpretation of entropy justifies the value of $S=0$ at $0K$
Allows us to define the absolute entropies of substances and to calculate the standard entropy change of a reaction.