Thermodynamics Terms

Step 1: Free energy change ( ) in reactions.
- Negative indicates that the reaction is spontaneous and can proceed without external energy input.
- Spontaneous reaction: The reaction will proceed in the direction where the free energy decreases.
- Exergonic reactions: These are reactions that release energy, corresponding to a negative .
- Option (B) is incorrect because negative indicates the free energy of the products is lower than the reactants, not higher.
- Option (C): While high activation energy can exist in some spontaneous reactions, it is not required for a negative .
Step 2: Conclusion. Thus, the correct options are spontaneous reaction and exergonic reactions.
Final Answer:

Step 1: Understand the third law of thermodynamics. The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero temperature (0 K) is exactly zero. This is because, at 0 K, the system is in its ground state, and no randomness or disorder exists.
Step 2: Explanation of other options.
- (B): This refers to the first and second laws of thermodynamics.
- (C): Entropy evolution with time is a broader concept covered by the second law of thermodynamics.
- (D): Conservation of mass is described by the law of conservation of mass, not the third law of thermodynamics.
Step 3: Conclusion.
Thus, the third law of thermodynamics specifically deals with the entropy of a perfect crystal at absolute zero.
Final Answer: