Week 1 Homework Question 4

[Carson Yoshida 3H]

PCl5 is placed in a sealed container at an initial pressure of 0.0220 bar. What is the total pressure at equilibrium?

I'm having trouble with this problem. I made an ICE box, plugged in my values to the Kp expression and solved for x using the quadratic formula. I ended up with -1+/- 0.0074. This gives me two negative values which I can't use for partial pressure. Am I doing this wrong?

[Charlie 2H]

If Kp=405 then after doing the icebox you should end up with 405=(0.0220-x)/x^2 which will result in x being equal to 0.00624 bar. To find the total pressure do 0.0220+x-x+x which will equal 0.0282.

[Carson Yoshida 3H]

If Kp=405 then after doing the icebox you should end up with 405=(0.0220-x)/x^2 which will result in x being equal to 0.00624 bar. To find the total pressure do 0.0220+x-x+x which will equal 0.0282.

Ahh thank you! I made an error when calculating the quadratic formula.

[Taylor Vargas]

If Kp=405 then after doing the icebox you should end up with 405=(0.0220-x)/x^2 which will result in x being equal to 0.00624 bar. To find the total pressure do 0.0220+x-x+x which will equal 0.0282.

Hi im a bit confused on why it would be 0.0220-x/x^2 instead of x^2/0.0220-x because isn't the reaction now going from right left since you are loosing product.

[Charlie 2H]

I believe that the reaction would still be going from right to left.