Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: SOS on February 14, 2011, 03:34:17 AM
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Is it asking for the freezing point depression when it says calculate the freezing point of a solution? How do I solve this problem..?
Calculate the freezing point of a solution containing 0.600kg of CHCl3 and 42.0g of C10H18O.
Which is the solute and which is the solvent? Do I use the formula DeltaTf = iKfm?
Here is my attempt:
Since CHCl3 has a bigger amount of grams (i converted the kg to grams to check which has bigger amount of grams), it is the solvent and C10H18O is the solute.
It wants the freezing point of the solution (which im assuming they want the freezing point depression of the solution) and
DeltaTf = iKfm
i = solvent does not dissolve so van't hoff factor is 1.
Kf of solvent = 4.68 degree C/m
m = 0.600 kg of the solvent
42g --> 0.272 moles of solute
0.272 mol of solute/0.600 kg of solvent = 0.453m
DeltaTf = (1)(4.68)(0.453)
= 2.12 degree celsius.
I got it wrong and my book says the answer is -65.6 degree celsius.
am I at least on the right track?
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It's asking for the depressed freezing point I think.
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edit: I think I got it..
After getting the 2.12, I am looking for the freezing point so I look at my solvent's normal freezing point temperature. And because it is depressing, I subtract it from 2.12.
Normal Freezing Point is -63.5 - 2.12 = -65.62.