Chapter 21, Problem 46PS

Interpretation Introduction

Interpretation:

To calculate the enthalpy and free energy change for the given reaction and check whether the reaction is exothermic or endothermic.

Concept introduction:

The Gibbs free energy or the free energy change is a thermodynamic quantity represented by $\Delta G^{\circ }$. The expression for the free energy change is:

${\text{Δ}}_{\text{r}}{G}^{\text{°}}=\sum n{\Delta }_f{G}^{\text{°}}\left(\text{products}\right)-\sum n{\Delta }_f{G}^{\text{°}}\left(\text{reactants}\right)$

The enthalpy change is expressed by the formula,

${\text{Δ}}_{\text{r}}{H}^{\text{°}}=\sum n{\Delta }_f{H}^{\text{°}}\left(\text{products}\right)-\sum n{\Delta }_f{H}^{\text{°}}\left(\text{reactants}\right)$

If the value of enthalpy change is negative, the reaction is exothermic.

If the value of free energy change is negative, then the reaction is product-favored at equilibrium.