Chapter 18, Problem 81A

Interpretation Introduction

Interpretation: The statement always true for the spontaneous reaction is to be explained.

Concept Introduction: A reaction is said to be spontaneous if the conditions under which it is taking place are such that the conditions favor the production of products.

Answer to Problem 81A

The reaction is spontaneous when free energy is released during the reaction.

Explanation of Solution

Reason for true statement:

c. The reaction is said to be spontaneous when free energy is released during the reaction. When Gibbs's free energy is negative, a process is considered to be spontaneous.

Reason for false statements:

a. Even if exothermic reactions have a positive enthalpy change, the reaction could have an unfavorable entropy change and an unfavorable Gibbs free energy change, and as a result, the reaction might not be spontaneous.

b. The reaction may not be spontaneous even if the entropy increases because it may have an unfavorable enthalpy change and an unfavorable Gibbs free energy change.

Conclusion

The reaction is spontaneous when free energy is released during the reaction.