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Homework Help: Find mass of product when given Kc, mass of reactant, but not volume

  1. Jan 31, 2010 #1
    1. The problem statement, all variables and given/known data
    Assume that at 25 C, with AlCl3 as a catalyst, the following equilibrium can be established between the liquids cyclohexane and methylcyclopentane.
    C6H12 <=> C5H9CH3HCH3
    Kc = 0.143
    If initially 1.00 x 10^2 g cyclohexane is present, what mass of methylcyclopentane will be present in the equilibrium mixture? (Hint: Does the volume of solution matter?)

    2. Relevant equations

    Kc = [product]/[reactant]

    3. The attempt at a solution
    I attempted to use ICE, but since I do not know the concentration (M) for the reactants, I do not know how to proceed.
    I could get the moles of cyclohexane, but then don't I need to convert it to M?

    Please advice. Thank you in advance.
  2. jcsd
  3. Feb 2, 2010 #2


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    HINT: Does the Volume matter?
    HINT2 : Does the mass matter? In a more abstract kinda way?

    The thing is :

    - moles initially of molecules (Cyclohex) = moles finally (Cyclohex + metpent)
    - mass initially = mass finally
    - and obviously Molecular mass of hex = Mol mass of pent
    Kc=mass pentane/mass hexane=moles pentane/moles hexane.

    So you end up with the amount % of hex that gets turned into pent.
  4. Feb 2, 2010 #3


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    Btw what is that:
    C6H12 <=> C5H9CH3HCH3

    the second isn't metylcyclopentane
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