The equilibrium constant Kc = 49 for the reaction: PCl3 (g) + Cl2 (g) ⇌ PCl5 (g)
at 230 °C. If 0.70 mol of PCl3 is added to 0.70 mol of Cl2 in a 1.00-L reaction vessel at 230 °C, what is the concentration of PCl3 when equilibrium has been established?
a. 0.59 M
b. 0.30 M
c. 0.11 M
d. 0.83 M