chem102L_Exp12 - Experiment 12 Colligative Properties...

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Experiment 12 – Colligative Properties Name Lab Day and Time TA Section Documentation GRADING RUBRIC Possible Points Points Received Introduction 10 Purpose of report Goals of the experiment Materials and Methods 20 Describe procedure in paragraph format following guidelines provided (-2 for each type of mistake) Results and Discussion 40 Inserted titles for tables Inserted graphs into template Inserted captions for each graph Showed complete sample calculations Summarized all data in tables Answered questions completely Error analysis Unknown Identification 10 Laboratory Technique 20 TOTAL (100) TA Comments/Suggestions: SPRING 2008
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C HEMISTRY 102L R EPORT T EMPLATE EXPT. Colligative Properties 12 12 Introduction The purpose of this report is analyze and present the data concerning the freezing point depression of a solution of cyclohexane and an unknown solute. Using knowledge of colligative properties and also including using the molality of that solution identity of the unknown solute was discovered. The objective of the experiment was to generate warming curves for both cyclohexane and the solution to determine the freezing point depression of the solution. Materials and Methods Before data was taken to determine the warming curve of cyclohexane, the temperature sensor was calibrated. The sensor recorded room temperature and the temperature of water brought to a boil with use of an immersion heater, stir plate and stir bar. After this calibration was complete, an ice bath was prepared in a 400-mL beaker, using about 35 grams of solid sodium chloride dissolved in around 175 mL of liquid water and chilled by a similar amount of solid water. The ice bath was then poured into a 600-mL beaker, leaving around 3 inches of space at the top of the beaker to place in a 125-mL Erlenmeyer flask to be filled with 25.05 mL of cyclohexane, measured into the flask with use of a buret. The Erlenmeyer flask was stopped using a one-hole rubber stopper with the temperature sensor inserted into the hole. The Erlenmeyer flask was clamped into the ice bath and the cyclohexane allowed to form crystals. Once crystals had formed, the Erlenmeyer flask was removed and the data was collected until the cyclohexane had reached a temperature between 12 and 15 C. The cyclohexane was then ˚ reinserted in to the ice bath and the data collection process was repeated for a total of four trials. The unknown was then weighed with use of an electronic balance and a mass of 0.717 grams was added to the cyclohexane. The solution was swirled until the all of the unknown solid had dissolved. The solution was then placed into the ice bath, allowed to form crystals and then removed from the ice bath. Data was taken as the solution melted until the temperature of the solution reached 10-15 C. This process was repeated for a total of four trials. The cyclohexane ˚ solution was then disposed in the “Liquid Organic Waste” container in the fume hood and the ice
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chem102L_Exp12 - Experiment 12 Colligative Properties...

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