It \( 427^{\circ} \mathrm{C} \), a 5.0 L flask contains 20.0 moles of \( \mathrm{HCl}, 18.0 \) noles of \( \mathrm{O}_{2}, 12.0 \mathrm{~mol} \) of \( \mathrm{Cl}_{2} \), and 5.9 moles of water apor at equilibrium. Calculate the \( \mathrm{K}_{\text {eq }} \) for the reaction:
\[
\mathrm{HCl}_{(\mathrm{g})}+\mathrm{O}_{2(\mathrm{~g})} \rightleftharpoons \mathrm{Cl}_{2(\mathrm{~g})}+\mathrm{H}_{2} \mathrm{O}_{(\mathrm{g})}
\]
