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Homework Help: Applications of Equilibrium Constants

  1. Jan 16, 2010 #1
    1. The problem statement, all variables and given/known data

    At 1285*C the equilibrium constant for the reaction [tex]Br_2 (g) \Leftrightarrow 2Br (g)[/tex]. A 0.200L vessel containing an equilibrium mixture of the gasses has 0.245g of [tex]Br_2[/tex](g) in it. What is the mass of Br(g) in the vessel?

    2. Relevant equations


    3. The attempt at a solution

    I have tried this 4-5 different ways at least and cannot get close to the answer. I started with this

    [tex]K_c = \frac{[Br]^{2}}{[Br_2]}[/tex]

    Rearrange that to solve for Br. I get...

    [tex][Br_2] \times K_c = [Br]^2[/tex]

    Then after that I am lost. I've tried converting Br_2 from grams to moles. Leaving it as grams and converting at the end. The answer in the book is in M, but I cannot even come close to that.

    Any hints? I know for sure just plugging in grams of Br_2 and K_c, then solving for x doesn't get me even in the ballpark.

    The book answer is 0.00767M. Which strangly enough is what I get what I convert 0.245g of Br_2 into M.

    The answer I get at the end is 0.0028 M Br.

    EDIT!! Nevermind. I am a moron. I had the answer right the whole time I just wasn't reading the answer book correctly. :blushing:
    Last edited: Jan 16, 2010
  2. jcsd
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