Homework Help: chemistry

Posted by Tina on Monday, May 2, 2011 at 12:56am.

Data:
freezing point of pure cyclohexane: 6.0 degrees celcius

Freezing point of unknown soluton: 1.6 degrees celcius

weight of cyclohexane: 40.0231g=0.0400231 kg
weight of unknown solute: 0.4872 g
K_f_ of cyclohexane: -20.00 degrees Celciusx kg/mole

questions:
1. what is the change in freezing point of cyclohexane?
2. what is the molarity of the solution?
3. what is the moleculr weight of the unknown solute?

chemistry - DrBob222, Monday, May 2, 2011 at 1:06pm
1. normal freezing point - freezing point soln = change.
2. I think you want molality and not molarity. delta T = Kf*m. Solve for m = molality.
3. molality = moles/kg solvent
Solve for moles.
Then moles = grams/molar mass. Solve for molar mass.

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