Chapter 21, Problem 21.125CP

Interpretation Introduction

Interpretation:

To determine the standard free energy change in kJ per mole of metal for decomposition of ${\text{M}}_{\text{2}}{\text{O}}_{\text{3}}$ (M= $\text{Fe}$ or $\text{Al}$ ) to the metal and ${\text{O}}_{\text{2}}$ gas. Also, to verify if these metals can be obtained by decomposition of their oxides under standard-state conditions.

Concept introduction:

The standard Gibbs free energy of formation of a compound is the change of Gibbs free energy that accompanies the formation of 1 moleof that substance from its component elements, at their standard states.

To determine:

The standard free energy change in kJ per mole of metal for decomposition of ${\text{M}}_{\text{2}}{\text{O}}_{\text{3}}$ (M= $\text{Fe}$ or $\text{Al}$ ) to the metal and ${\text{O}}_{\text{2}}$ gas. Also, to verify, if these metals can be obtained by decomposition of their oxides under standard-state conditions.

Given:

Free energy change in values for ${\text{M}}_{\text{2}}{\text{O}}_{\text{3}}$ (M= $\text{Fe}$ or $\text{Al}$ ) per mole of metal for decomposition of ${\text{M}}_{\text{2}}{\text{O}}_{\text{3}}$ (M= $\text{Fe}$ or $\text{Al}$ ) to the metal and ${\text{O}}_{\text{2}}$ gas.
Let us take ?G values for ${\text{Al}}_{\text{2}}{\text{O}}_{\text{3}}$ from thermodynamic data

  ${\text{Al}}_{\text{2}}{\text{O}}_{\text{3}}$ = -9.50 kJ/mol,

  ${\text{O}}_{\text{2}}$ = 0 kJ/mol,

  $\text{Al}$ = 0 kJ/mol.