January 22, 2017

Homework Help: Chemistry

Posted by Hannah on Monday, February 20, 2012 at 4:23pm.

I had to perform an experiment for the freezing point depression in which we had to determine the frezzing points of water as a pure solvent, sodium chloride, sucrose, and ethylene glycol.
We had to work with a partner so I completed the experiment for water, NaCl, and the glycol and had to get the info for sucrose from my partner. The data that was collected was the freezing pint of DI water which was the corrected value for the thermometer that I used. We had to record the temp every 30 seconds until we saw ice crystals. We had to do the same thing for the NaCl, sucrose, and gycol. For the NaCl we started at 0.5 min in which the temp was 15.0 degrees celsius and crystals formed at 10.5 min at -2.0 degrees celsius.

For my calculations the first thing I need to calculate is the delta Tf. Is this just the initial temp - the final temp?

Chemistry - Hannah, Saturday, February 18, 2012 at 4:22pm
The very frist thing that was asked for the calculations was the freezing point in degrees celsius for NaCl and Sucrose and I put -2.0C for NaCl and for sucrose my partner got -4.0C.

Chemistry - Hannah, Saturday, February 18, 2012 at 5:14pm
In my lab book it just says delta Tf = the change in the freezing point (Tsolution - Tpure solvent = negative number)

Chemistry - DrBob222, Saturday, February 18, 2012 at 6:56pm
In your initial post you said you had to determine the freezing point of pure water (that's the solvent). So delta T = f.p. soln - f.p. pure water.

I understand that to get delta T i had to do the fp of the soln - fp of water. My freezing point of the DI water was 0.5C so I have to subtract this from the fp that I got for NaCl and sucrose, is that correct?

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