Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: rudiment274 on November 25, 2014, 07:17:11 PM
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Hello! I did an experiment on determining molecular weight through freezing point depression, and I just wanted to ask a few things for clarification.
My solvent was benzophenone (BZP). If some of the solvent adheres to the test tube walls above the solution, would the calculated molecular weight be too low? I think yes because not all the BZP reacted in the solution.
Does the same concept apply to solutes?
And if the freezing point depression is calculated from super-cooled BZP, would the molecular wight be too high because of the solid formed?
Thank you!
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If some of the solvent adheres to the test tube walls above the solution, would the calculated molecular weight be too low?
Yes, but it depends how much solvent whether it makes a significant difference.
Does the same concept apply to solutes?
Yes, then the calculated MW will be high.
And if the freezing point depression is calculated from super-cooled BZP, would the molecular wight be too high because of the solid formed?
Don't know what you mean by "because of the solid formed", but if the liquid is supercooled then the freezing point will tell you nothing - it has to freeze at its thermodynamic freezing point. If you can't get it to do this, try measuring the melting point.