Introduction to Equilibrium Practice Test

In a sealed container, the reversible reaction $\text{PCl}_5(g)\rightleftharpoons \text{PCl}_3(g)+\text{Cl}_2(g)$ reaches a point where the measured amounts of each gas do not change with time. Which statement best describes the system at equilibrium?

A sealed vessel contains the reversible reaction $\text{PCl}_5(g) \rightleftharpoons \text{PCl}_3(g) + \text{Cl}_2(g)$ at constant temperature. After some time, the amounts of each gas remain constant. Which statement correctly describes the system at equilibrium?