A student ran the following reaction in the laboratory at 494 K: PCl3(g) Cl2(g) PCl5(g) When he introduced PCl3(g) and Cl2(g) into a 1.00 L evacuated container, so that the initial partial pressure of PCl3 was 1.75 atm and the initial partial pressure of Cl2 was 0.989 atm, he found that the equilibrium partial pressure of PCl5 was 0.721 atm. Calculate the equilibrium constant, Kp, he obtained for this reaction.