Chapter 21, Problem 23PS

Interpretation Introduction

Interpretation:

The value of ${\text{Δ}}_{\text{r}}{H}^{\text{°}}$, ${\text{Δ}}_{\text{r}}{S}^{\text{°}}$ and ${\Delta }_{\text{r}}{G}^{\circ }$ for the preparation of hydrogen should be calculated.

Concept introduction:

The Gibbs free energy or the free energy change is a thermodynamic quantity represented by ${\Delta }_{\text{r}}{G}^{\circ }$. It is related to entropy and entropy by the following expression,

${\Delta }_{\text{r}}{G}^{\circ }={\Delta }_{\text{r}}{H}^{\circ }-T{\Delta }_{\text{r}}{S}^{\circ }$

Here, ${\Delta }_{\text{r}}{H}^{\circ }$ is the change in enthalpy and ${\Delta }_{\text{r}}{S}^{\circ }$ is the change in entropy.

The enthalpy change is expressed as,

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

The entropy change is expressed as,

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