In this experiment you will determine the molar mass of an unknown solid by dissolving a pre-weighed sample in a solvent, and measuring the resulting freezing point depression of the solvent.
To establish the proper straight line in the solid-liquid region it is necessary to record the temperature until the trend with time is smooth and clearly established.
This activity will provide a real world example of how a pure substance candle wax changes from one state liquid to another solid. Objectives To determine the molar mass of an unknown solid using the colligative property of freezing point depression.
Constructing explanations and designing solutions. Using your beaker tongs, place the beaker of hot water onto the lab bench well away from the test tube. Para-dichlorobenzene is used in mothballs and urinal cakes, and so it may have a familiar smell, however direct inhalation of its vapors may be harmful or even toxic.
Stir the contents of the large test tube by raising the glass loop up and down slowly to melt any remaining solid PDB.
Stir well to mix the unknown with the PDB thoroughly. The acetone and para-dichlorobenzene must not go down the sink! This will serve as a hot water bath for the experiment. At first the temperature will fall quite rapidly.
Insert the thermometer into the test-tube and record the initial temperature. Weigh a clean dry large test tube using an electronic balance, and record its mass. Monitor the temperature of the PDB as it cools. After transferring this additional unknown to the large test tube, weigh the remaining unknown sample and its container.
Note the temperature at which any solid first appears. Monitor the temperature of the PDB-unknown mixture as before. Structure and Properties of Matter - The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.
Science and Engineering Practice 6: Calculate the mass of unknown sample transferred to the test tube by difference. It is also practical experience that liquid wax freezes into solid wax.
The freezing point of the pure liquid is the constant temperature observed while the liquid is freezing to a solid.
As the temperature of the water bath reaches the melting point of the PDB, it will begin to melt.
Add this mass to the mass of unknown transferred in Step 8 to obtain the total mass of unknown added to the large test tube.
This behavior is shown in Figure 3 below. Raise the hot water bath around the large test tube and heat the PDB-unknown mixture until it is completely melted.Purpose: The purpose of this lab was to determine the freezing point of pure water, the experimental van’t Hoff factor for a substance and the molar mass of an unknown solution.
Lab 7 - Determination of the Molar Mass of an Unknown Solid by Freezing Point Depression Goal and Overview In the first part of the lab, a series of solutions will be made in order to determine the freezing point depression constant, K f, for billsimas.com freezing points of these solutions, which will contain known amounts.
Experiment 12 – Freezing Point of Solutions A solution freezes at a lower temperature than does the pure solvent. This phenomenon is called freezing point billsimas.com freezing point depression of a solution is a colligative property of the.
View Lab Report - Experiment 3 - Determination of a Molar Mass by Freezing Point Depression from CHM at University of Toronto, Mississauga.
Experiment 3 Determination of a Molar Mass by Freezing%(18). Experiment 5 Freezing Point Depression OUTCOMES After completing this experiment, the student should be able to: After determining the freezing point and actual values from your lab section and calculate the average value of K f for t-butyl alcohol.
6. How constant was the K f. Lab 3 - Freezing Point Depression; Lab 3 - Freezing Point Depression In Part A of this experiment, you will determine the freezing point of pure stearic acid. In Part B, you will measure the freezing point depression caused by adding varying amounts of lauric acid to stearic acid and compare these measured values to your calculated values.Download