16.4 Exercise 6

Given:
$\text{P}_{4} \left(s\right) + \text{5O}_{2} \left(g\right) \rightarrow \text{P}_{4} \text{O}_{10} \left(s\right) \Delta G ° = −\text{2697}.\text{0 kJ}/\text{mol}$
$\text{2H}_{2} \left(g\right) + \text{O}_{2} \left(g\right) \rightarrow \text{2H}_{2} \text{O} \left(g\right) \Delta G ° = −\text{457}.\text{18 kJ}/\text{mol}$
$\text{6H}_{2} \text{O} \left(g\right) + \text{P}_{4} \text{O}_{10} \left(s\right) \rightarrow \text{4H}_{3} \text{PO}_{4} \left(l\right) \Delta G ° = −\text{428}.\text{66 kJ}/\text{mol}$

(a) Determine the standard free energy of formation, $\Delta G_{\text{f}}^{\circ} ,$ for phosphoric acid.

(b) How does your calculated result compare to the value in Appendix G? Explain.