uncch102L_exp12 - Experiment 12 Colligative Properites...

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Experiment 12 – Colligative Properites Summer 2010 Name I HAVE USED THIS LAB! IF YOU USE MY LABE VERBATUM, YOU WILL BE CAUGHT! Point Summary (See Blackboard for detailed grading rubric) Superior Excellent Satisfactory Fair Poor Omitted Introduction •Purpose of Report •Goals of Experiment Materials and Methods Results and Discussion •Description of data •Data Tables •Data Table Titles •Graphs •Figure Captions •Sample Calculations •Systematic Error •Random Error •Discussion of discrepancies Other Lab Technique TOTAL POINTS TA Comments/Suggestions:
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C HEMISTRY 102L R EPORT T EMPLATE EXPT. Colligative Properties 12 12 Introduction The purpose of this report is to show warming and cooling trends in a pure solvent and a solvent with an unknown substance and to report the identity of the unknown substance used in the experiment. The freezing-point depression equation, the average freezing points of both the pure solvent and the solution, and the mass of the solvent and unknown will be used to determine the identity of the unknown solid. The objective of the experiment was to understand colligative properties and to use them to determine the molar mass and identity of an unknown substance. Materials and Methods The procedure was taken from Experiment 12: Colligative Properties- Freezing Point Depression and Molar Mass in the UNC-CH Fall 2010 CHEM-102L Lab Manual. An ice bath containing approximately 35 g (1.7mol) of solid NaCl, ice, and water was prepared in a 600-mL beaker and was placed on a stir plate. The ice bath solution was allowed to stir for the entirety of the experiment and was tended to throughout to maintain a low temperature. Approximately 25 mL of cyclohexane from a buret was transferred to a 125-mL Erlenmeyer flask, the final and initial buret readings can be found in Table 1. The flask was sealed with a rubber stopper equipped with a temperature sensor. The Erlenmeyer flask was clamped into the ice bath and allowed to cool until the cyclohexane froze. Temperature readings were taken every 30 seconds in DataStudio, and when a stable temperature was reached, and the cyclohexane was frozen the flask was removed from the ice bath and allowed to warm. The cyclohexane was allowed to warm until the temperature reached 12-15ºC, while it was melting temperature readings were taken every 30 seconds and recorded in DataStudio. The cooling and warming was then repeated twice more.
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This note was uploaded on 05/15/2011 for the course CHEM 102L taught by Professor N/a during the Fall '07 term at UNC.

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uncch102L_exp12 - Experiment 12 Colligative Properites...

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