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!

Need major help

  1. Apr 15, 2006 #1
    I'm learning equilibirum in class, but I am stuck on this question. DOes anyone how how to do this problem? I use the quadratic formula but end end with answers A and B, but the correct answer is A. Can someone show me step by step how to do this problem? thanks

    9. At a certain temperature, T, K for the reaction below is 7.5 liters/mole.
    2NO2 <===> N2O4
    If 2.0 moles of NO2 are placed in a 2.0-liter container and permitted to react at this temperature, what will be the concentration of N2O4 at equilibrium?

    a) 0.39 moles/liter
    b) 0.65 moles/liter
    c) 0.82 moles/liter
    d) 7.5 moles/liter
    e) none of these
     
  2. jcsd
  3. Apr 15, 2006 #2
    You did the problem correctly. You end up having to solve the quadratic equation 30.x2 - 31x + 7.5 = 0. You get the answers of x = .39 and x = .65.

    Now, think about the problem. You are starting with 1.0 M NO2, correct? You should notice that the equilibrium concentration of NO2 will be 1.0 - 2x, and the equilibrium concentration of N2O4 will be x.

    If x was .65, then 1.0 - 2x would yield a negative concentration, which is physically impossible. Therefore, the only correct answer can be [N2O4] = .39 M because 1.0 - 2(.39) gives you a positive concentration.
     
    Last edited: Apr 15, 2006
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Need major help
  1. Need help (Replies: 2)

  2. Help needed (Replies: 6)

  3. Need help (Replies: 5)

Loading...