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?
6 answers
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.
Yes, the f.p. is when the ice crystals started forming. Generally the temperature of a mixture like this reaches a plateau and stays at that temp from beginning of freezing until all is frozen. I take that plateau. For the delta T, I don't know what you're calling Tf and Ti. What you want to use for delta T is
f.p. DI water - f.p. soln
f.p. DI water - f.p. soln
In my lab book it just says delta Tf = the change in the freezing point (Tsolution - Tpure solvent = negative number)
So for the delta T of NaCl I do 0.50 which was the freezing point - the solvent? I do not know how to find the fp of the solvent.
So for the delta T of NaCl I do 0.50 which was the freezing point - the solvent? I do not know how to find the fp of the solvent.
The next calculation is to actually find the mass of solvent(kg) for both NaCl and sucrose and my lab books says to assume that the density of water is 1.00g/mL.
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.
We had to measure out 5.800g of NaCl and record the exact weight. First I weighed the measuring boat and then I poured in the NaCl so to get the exact weight I subtracted the mass of the measuring boat with NaCl from the mass of just the boat. Is this correct?
2 answers