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Posted by on Sunday, November 6, 2011 at 9:41pm.

A 13.03 g sample contains only ethylene glycol (C2H6O2) and propylene glycol (C3H8O2). When the sample is added to 100.0g of pure water, the resulting solution has a freezing point of -3.5C. What is the percent composition of ethylene glycol and propylene glycol in the original sample?

  • chemistry - , Sunday, November 6, 2011 at 11:35pm

    delta T = Kf*m
    Solve for m

    m = moles/kg solvent
    Solve for moles.

    moles = grams/molar mass
    Solve for molar mass.

    Then let X = fraction of C2H6O2
    and 1-X = fraction of C3H8O2
    --------------------------
    X(molar mass C2H6O2) + (1-x)(molar mass C3H8O2) = molar mass of the mixture.
    Then convert X to percent and 1-X to percent. I think the answer is about 48% and 52% respectively but these are approximations.Post your work if you get stuck.

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