1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Chemical Equilibria with Gases

  1. Mar 19, 2012 #1
    1. The problem statement, all variables and given/known data

    When 1.000 mol PCl5 is intorduced into a 5.000L container @500K, 78.50% of PCl5 dissociates to give equilibrium mixture PCl5, PCl3, Cl2 : PCl5--->PCl3+Cl2 (this eq. is reversible)

    (a) calculate Kc and Kp
    (b) if the initial concentrations are [PCl5]=.500M, [PCl3]=.150M, and [Cl2=.600], in which direction does the rx proceed to reach equilibrium? what are the concentrations when the mixture reaches equilibrium?

    2. Relevant equations

    Kc=[Products]/[reactants]
    Kp=Kc(RT)^n


    3. The attempt at a solution

    I attempted to find Kc of the initial problem, by getting the molarity (.2) of the reactant. I then multiplied by .785 to get the percent to put in the numerator, but am not getting the right answer in the book. I know in part b i must use the chart to convert to quadratic equation, but am having trouble with the first part (surprisingly, as its usually the second part which gives me trouble). I have tried this either which way and still can not get the right answer. Any input would be great. Thanks!
     
  2. jcsd
  3. Mar 19, 2012 #2

    Borek

    User Avatar

    Staff: Mentor

    Not seeing all the numbers it is hard to say - you can be missing something, it can be just a math error. Please show your complete work, step by step.
     
  4. Mar 20, 2012 #3
    Yeah turns out I had the right idea, but didn't do it right. I went and saw my professor and he walked me through it. I had assumed that the .2M stayed the same for the PCl5, however, when the equation went to equilibrium, I had forgotten to use the 21.5% that was left, as the PCl5.

    .2M *.785 gives .157, then .2-.157 gives .043, which is what I should have used for the PCl5 @ equilibrium, rather than the .2. Thanks for the input. Glad to know that people actually respond and are willing to help out.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Chemical Equilibria with Gases
  1. Gas Equilibria (Replies: 6)

Loading...