Phosphorus pentachloride decomposes according to the chemical equation
PCl5(g) ⇌ PCl3(g) + Cl2(g)
A 0.304 mol sample of PCl5(g) is injected into an empty 4.75 L reaction vessel held at 250 °C. Calculate the concentrations of PCl5(g) and PCl3(g) at equilibrium.