FREEZING-POINT-DEPRESSION-LAB

FREEZING-POINT-DEPRESSION-LAB - FREEZING POINT DEPRESSION...

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FREEZING POINT DEPRESSION LAB PURPOSE The purpose of this experiment is to demonstrate the effect of solutes on the freezing point of water. DESCRIPTION This experiment is suitable for a first-year course. It could also be included in a second-year course as part of a unit on colligative properties. The calculations require the use of the equation, T = (K f ) (m) (i) . In the first part of the experiment, various solutes are added to water and the resultant freezing points of the solutions are determined. The value of i , dissolved particles per formula unit, is calculated. In the second part, the molar mass of glycerol is determined. TIME REQUIRED Two lab periods. MATERIALS Chemicals: Ice, C 12 H 22 O 11 (sucrose), NaCl and unknown ( nonelectrolyte ) Equipment: Test tubes, thermometer or thermo couples and Vernier LabQuest, 400-mL beaker, 100-mL beakers, 100-mL graduated cylinder, stirring rods and weighing dishes. HAZARDS Laboratory chemical should not be ingested. The ice used in the experiment could become contaminated with chemicals by accident; students should be warned not to eat the ice. Goggles must be worn throughout the experiment. MODIFICATIONS/SUBSTITUTIONS 1. Table sugar may be substituted for reagent grade sucrose. 2. Table salt can be substituted for laboratory grade NaCl. 3. A 10-ounce Styrofoam cups can be substituted for the 400-mL beaker. Adatped from http://www.woodrow.org/teachers/ci/1986/exp9.html
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PROCEDURE Preparation of Ice Bath 1. Fill the large beaker 3/4 full with ice. 2. Cover the ice with 1/4 to 1/2 inches of table salt. 3.
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FREEZING-POINT-DEPRESSION-LAB - FREEZING POINT DEPRESSION...

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