Chapter 20.3, Problem 20.6AFP

(a)

Interpretation Introduction

Interpretation: The sign of change in entropy for the given reaction needs to be determined.

Concept Introduction: Entropy of any substance is defined by its degree of randomness. It increases with the molecular weight of a substance and its complexity. If concentration and pressure increase, the entropy of the substance decreases. Also, it depends on the state of the substance, for example, solid substances have less entropy as compared to liquid and gaseous substances have maximum entropy. For substances in the same state, the substance with higher molecular weight has greater entropy.

(b)

Interpretation Introduction

Interpretation: The sign of change in enthalpy of the reaction needs to be determined if the reaction is spontaneous only above $325{}^{\text{o}}\text{C}$ .

Concept Introduction: The change in Gibbs free energy $\Delta G$ , change in enthalpy $\Delta H$ , and change in entropy $\Delta S$ are related to each other as follows:

  $\Delta G=\Delta H-T\Delta S$

Here, T is the absolute temperature.