Question

Identify the correct statement regarding entropy.

• A. at absolute zero, the entropy of a perfectly crystalline substance is +ve
• B. at absolute zero, the entropy of a perfectly crystalline substance is zero
• C. at $0^{o}C$ the entropy of a perfectly crystalline substance is taken to be zero
• D. at absolute zero to temperature the entropy of all crystalline substances is taken to be zero

Answer 1

Answer: (B)

at absolute zero, the entropy of a perfectly crystalline substance is zero

Third law states that entropy of a perfect crystal is zero at 0 Kelvin. This is because system is in ground state with minimum possible energy and perfect crystal has only one minimum energy state. So particle can't exhibit motion.