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Chemistry freezing point and determination of molecular formula

  1. Mar 30, 2009 #1
    1. The problem statement, all variables and given/known data[/b]
    question 1: Calculate the mole fraction of benzene in benzene-toluene solution that is in equilibrium at 25 deg. Celsius with a vapor pressure that contains 62% mol Benzene. At 25 deg. Celsisus the vapor pressures of benzene and toluene are 95.1 mm Hg and 28.4 mm Hg respectively. Kf of Benzene= 5.50 deg Celsius.

    question 2: Coniferin is a glycoside (derivative of sugar) found in conifers such as fir trees. When a 1.205 g smaple of coniferin is subjected to combustion analysis, the products are 0.698 g H20 and 2.479 g CO2. In another experiment, a 2.216 g sample of coniferin is dissolved in 46.68 g water, and the normal boiling point of the solution is 100.068 deg. Celsius. What is the molecular formula of coniferin?

    Help on one or both of these questions would be greatly appreciated. Please provide explanation or mathematical work showing how you got to your answer.

    2. Relevant equations
    Delta T=Kb x molality
    Ptotal= P(benzene)Molfract.(benz) + P(toluene)Molfract.(tol)

    3. The attempt at a solution
    1. ptot=95.1(?) + 28.4(0.38) after that i got stuck.

    2. For this one, I know you find moles each of H20 and CO2. Then you need to use the boiling point and somehow find moles of the solvent to get molar mass after changing molality to g.
  2. jcsd
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