Chapter 18, Problem 42E

Interpretation Introduction

Interpretation:

The values of ${\text{ΔH}}^{\text{0}},{\text{ ΔS}}^{\text{0}}{\text{, ΔG}}^{\text{0}}$ need to be deduced for the following reaction:

  ${\text{N}}_{\text{2}}{\text{(g) + O}}_2\text{(g) }\to \text{2NO}(\text{g})$

Concept Introduction:

The standard enthalpy change for a reaction ${\text{ΔH}}_{\text{R}}^{\text{0}}$ measured at 25°C and 1 atm is given in terms of the difference in the standard enthalpy of formation of the products and that of reactants.

  ${\text{ΔH}}_{\text{R}}^{\text{0}}\text{ = }{\displaystyle \sum {\text{n}}_{\text{p}}{\text{ΔH}}_{\text{f}}^{\text{0}}}\text{(products) - }{\displaystyle \sum {\text{n}}_{\text{r}}{\text{ΔH}}_{\text{f}}^{\text{0}}}\text{(reactants) ------(1)}$

Here, n_p and n_r are the number of moles of the products and reactants

The standard Gibbs free energy change for a reaction ${\text{ΔG}}^{\text{0}}$ measured at 25°C and 1 atm pressure is given in terms of the difference in the standard free energy of formation of the products and that of reactants.

  $\Delta {\text{G}}_{\text{R}}^{\text{0}}\text{ = }{\displaystyle \sum {\text{n}}_{\text{p}}{\text{ΔG}}_{\text{f}}^{\text{0}}}\text{(products) - }{\displaystyle \sum {\text{n}}_{\text{r}}{\text{ΔG}}_{\text{f}}^{\text{0}}}\text{(reactants) ------(2)}$

The standard entropy change for a reaction ${\text{ΔS}}^{\text{0}}$ measured at 25°C and 1 atm pressure is given in terms of the difference in the standard entropy of formation of the products and that of reactants.

  $\Delta {\text{S}}_{\text{R}}^{\text{0}}\text{ = }{\displaystyle \sum {\text{n}}_{\text{p}}{\text{ΔS}}_{\text{f}}^{\text{0}}}\text{(products) - }{\displaystyle \sum {\text{n}}_{\text{r}}{\text{ΔS}}_{\text{f}}^{\text{0}}}\text{(reactants) ------(3)}$