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Homework Help: Help in equillibrium problem with directon of net change

  1. Feb 9, 2008 #1
    1. The problem statement, all variables and given/known data

    The following amounts of substances are added to a 7.25 L reaction vessel at 773K:
    (.103 mol CO) , (.205 mol H2), ( 2.1 mol CH4), ( 3.15 mol H20). In what direction will a net reaction occur to react equilibrium.

    CO(g) + 3H2(g) --------> CH4(g) + H20 (g)

    Kp= 102 at 773K

    The answer to this problem is a slight net reaction occurs to the right because QP (98.4) is slightly less than Kp (102)

    The problem i have is everytime i try to do the work i cant get the Qp to = 98.4

    If someone will help me i will be very greatful

    2. Relevant equations

    3. The attempt at a solution

    here is my attempt sry i forgot to post it

    first i put all the moles in molarity and got the folloying
    CO--- .42 M
    H2--- .28
    CH4--- .014
    H2) --- 2x10-5 when you cube it cause of the coefficient

    Then i put a Qp equation

    Qp= ( .42)(.28)
    ------( .014)(2e-5)

    Final answer i got was Qp= 420000 way off i cant figure out why
    Last edited: Feb 9, 2008
  2. jcsd
  3. Feb 13, 2008 #2


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    Science Advisor
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    Gold Member

    The reaction quotient (Qp) in this case refers to the partial pressures of each of the species (rather than molarity). I believe the exponent for each of the partial pressures if given by the mole fraction of each species.
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