Which of the following statements concerning the second and third laws of thermodynamics is/are true? (I) When the change in entropy of the system is equal in magnitude and opposite in sign to the change in entropy of the surroundings, the change in entropy of the universe is zero. (II) The change in entropy of the universe can be rewritten as −∆Gsytem/T. (III) In a perfect, pure crystal at absolute zero the entropy of the system is zero.
1. III only
2. II, III
3. I only
4. I, III
5. II only
6. I, II, III
7. I, II
Correct option 6. I, II, III
Explanation:
Statement I is true; the second law equation states that the change in entropy of the universe is the sum of the change in entropy of the system and the surroundings. Statement II is true; this is a mathematical identity derived from the second law equation. Statement III is true; the third law states that as the temperature of a system approaches absolute zero, the entropy of the system approaches its minimum, which in the case of a perfect crystalline solid, is zero.