Experiment 3 - Determination of a Molar Mass by Freezing Point Depression - Experiment 3 Determination of a Molar Mass by Freezing Point Depression

Experiment 3 - Determination of a Molar Mass by Freezing Point Depression

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Experiment 3 Determination of a Molar Mass by Freezing Point Depression Student Name: Adam Sadowski Student Number: 1000142071 Other Member(s) of the Team: Kartik Moza Practical Section Number: 0122 Date the Experiment was Performed: 01/03/2013 Date the Report was Submitted: 08/03/2013 Submitted to Dr. I-San Chan
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2 Purpose Molar mass determination allows for the identification and oftentimes the discovery of an unknown compound; it has contributed to our recognizing over 70 million inorganic and organic substances. 2 Using the colligative property of freezing-point depression, the molar mass of an unknown, non-volatile solute will be determined. Because the vapor pressure of a solution is always lower than that of its solvent, the temperature at which a solution’s vapor pressure equals that of its solvent (i.e. the freezing point) will be lower when the solution contains a non-volatile solute. The freezing-point depression is proportional to molality, the molal freezing point depression constant and I (the number of particles of solute when in solution): ΔT = i K f m The freezing point of the pure solvent cyclohexane and of solutions containing cyclohexane with an unknown solute will be found by plotting cooling curves (temperature vs. time). Experimental Method Preparing of an ice-water bath and the solutions to be contained therein, as well as the
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