Chapter 5, Problem 5.13E

For the reaction

${\text{2SO}}_3(\text{g})\rightleftharpoons {\text{2SO}}_2(\text{g})+{\text{O}}_{\text{2}}(\text{g})$

when $2\text{mol}$ of ${\text{SO}}_3$ is added to a flask at $10\text{L}$ and $350.\text{K}$ at fixed volume, at equilibrium the ratio of ${\text{SO}}_2:{\text{SO}}_3$ is $\text{0}\text{.663}$. What is the value of equilibrium constant? What is $\Delta G°$ at this temperature?