K = 0.040 for the reaction below at 450 °C. If the reaction starts with 0.20 M Cl2 and 0.20 M PCl3, what concentration of PCl5 will be present at equilibrium? PCl5(g) PCl3(g) + Cl2(g) I know that the answer is 0.13M but can someone explain how to get it?

Question

K = 0.040 for the reaction below at 450 °C.  If the reaction starts with 0.20 M Cl2 and 0.20 M PCl3, what concentration of PCl5 will be present at equilibrium? 

PCl5(g)  <====>  PCl3(g)   +  Cl2(g)

I know that the answer is 0.13M but can someone explain how to get it?

cuanchi · Answer

are you sure that is the answer? 0.13M or 0.31M??