Achieve Question 4 Help

[106226281]

Hello everyone
Question 4 on the achieve asks: At a certain temperature, the given reaction has an equilibrium constant of K, = 375
PC1,(g) + C12(g) = PCl5(g)
PCls is placed in a sealed container at an initial pressure of 0.0520 bar. What is the total pressure at equilibrium?
So i set up my ice table and the changes for PCl3 is +x, for Cl2 its +2 and for Pcl5 its -x. At equillibrium I got PCl3 is +x Cl2 is +x and PCl5 is 0.0520-x.

Then I put all of this into P/R formula, which is 375=0.0520-x/x^2. Using the quadratic formula I got x1=-0.013 and x^2=0.011. Where do I go from here? I am confused, any help would be appreciated. Thank you!

[Kyle_Phong_2J]

Since you know it doesn't make sense to have a negative x-value, you can disregard the -0.013. Then, you use 0.011 as x and add all the pressures together for the total pressure at equilibrium. It would look like x + x + 0.071-x since these are the pressures at equilibrium.

[Michael_Kelly_2L]

Since the question asks for the TOTAL pressure at equilibrium, you want to find the equilibrium concentrations of PCl3, Cl2, and PCl5 and then add them together.

Using x = 0.011 (the positive value you get from solving the quadratic equation), you find the PCl3 and Cl2 = 0.011 and PCl5 = 0.0520 - 0.011 = 0.041 so your total pressure = 0.011 + 0.011 + 0.041 = 0.063 bar.

Hope this helps! :)