Freezing Point Depression- Lauric Acid Expt. 10 PDF

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Experiment 10 lab report...

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Freezing Point Depression: Lauric Acid Expt. 10 Introduction When a substance solidifies, the molecules come into a certain arrangement. In some cases the molecules become very closely packed and form a very dense solid. In the case of water, hydrogen bonding takes over when the molecules have such low kinetic energy. Since the distance between the hydrogen bond is longer in solids, the solid state will be less dense. In the process of freezing, impurities can slow down the process, and in this experiment we will be testing how solute affects the melting/freezing point of a substance. Melting and freezing points of substances are very similar, and we will use LabPro to determine the freezing point depression constant (Kf) for lauric acid, which is a nonelectrolyte. [For strong electrolyte solutions, the van’t Hoff factor (i) must be considered]. ΔT= Kf m Molality: the number of moles of solute, divided by the mass of the solvent (kg)

Procedure 1. Get LabPro set up, and you can use a temperature pobe to determine the freezing point of lauric acid. 2. Place the test tube in the beaker of hot water and melt the lauric acid, swirl the test tube gently 3. When the lauric acid fully melts put in the temperature probe into the test tube, fully immersing the tip, and acquire the data. 4. Put the test tube into a room temperature water bath, and constantly stir with the temperature probe. 5. Record the data up to the point when the temperature starts to trail off and drops below 30 degrees Celsius. 6. Obtain a test tube with 8g of lauric acid and 0.75g of benzoic acid, place it in the water bath and melt it. 7. Take it out of the water bath and record the freezing curve with the temperature probe 8. Repeat the previous procedure, but this time around use 8g of solvent and 1.5g of solute.

Equations ΔT= Kfm

Observation Mistakes could have been made in this experiment when shaking the solutions, different rates could have been implemented and that could have affected the temperature. Another possible source would be the measure of the concentrations and mass of the solute and solvent.

Calculations

Discussion / Conclusion After conducting the experiment, we could calculate the freezing/melting point of lauric acid, and the effect solutes have in the freezing process. Mistakes could have been made in this experiment when shaking the solutions, different rates could have been implemented and that could have affected the temperature. Another possible source would be the measure of the concentrations and mass of the solute and solvent....