Please help me with this chemistry problem...

Discussion in 'Pre-Medical - MD' started by NubianPrincess, Apr 14, 2002.

  1. NubianPrincess

    NubianPrincess Perpetually Bored

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    In the reaction CO(g) + CL2(g) <--> CoCL2(g),
    Kc = 1.2*10^3 at 395 degrees Celcius. What is the equilibrium value of [COCL2] if at equilibrium [CO]=2[CL2] = 1/2[COCL2] ?
    Any help would be greatly appreciated.
     
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  3. imtiaz

    imtiaz i cant translate stupid
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    Easy.

    Kc = products/reactants

    Kc = [COCl2]/[CO][Cl2]

    [CO]= 1/2[COCl2]

    2[Cl2] = 1/2[COCl2] so
    [Cl2] = 1/4[COCl2]

    [COCl2] equals [COCl2] (duh)

    1.2e3 = [COCl2]/[CO]*[Cl2]
    1.2e3 = [COCl2]/(1/2[COCl2])*(1/4[COCl2])
    1.2e3 = [COCl2]/1/8[COCl2]^2
    1.2e3 = 1/[COCl2]*1/8
    (1/8)*1.2e3 = 1/[COCl2]
    1/((1/8)*1.2e3) = [COCl2]

    There you go. :D
     
  4. Mr.D

    Mr.D insipidus maximus

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    You're going to have do some substitution to get the anser since they give you a relationship between the reactants and products and the K. With this in mind try to substitue a value for [COCl2], such as x, and then use the same variable to get the other 2 equilibrium concentrations (ie. [Cl2]=4x, [CO]=2x). Now set your equilibrium expression K= [products]/[reactants] using the substituted values from above, and simply solve for x (recall [COCl2] = x). The answer I got was 1.04E-4. One more thing, PURE solids and liquids have activities equal to 1, therefore you don't have to worry about incorporating their values into an equilibrium expression. Hope this helps.
     
  5. imtiaz

    imtiaz i cant translate stupid
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    Everything is in the gas phase, so it will be partial pressures instead of concentrations, but it's the same deal. If you did have liquids and solids, it wouldn't be a Kc, but a Keq. :p
     
  6. NubianPrincess

    NubianPrincess Perpetually Bored

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    Thank you. I tried the substitution method but got really large values, so I'll try it again.
    On another note, I HATE the last two weeks of class.
    Thanks again :)
    Nubian
     

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