1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

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


    User Avatar

    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


    User Avatar

    Btw what is that:
    C6H12 <=> C5H9CH3HCH3

    the second isn't metylcyclopentane
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook