04 Freeze Pt LQ (Autosaved).docx - LabQuest Using Freezing-Point Depression to Find Molecular Weight When a solute is dissolved in a solvent the

04 Freeze Pt LQ (Autosaved).docx - LabQuest Using...

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LabQuestUsing Freezing-Point Depressionto Find Molecular WeightWhen a solute is dissolved in a solvent, the freezing temperature is lowered in proportion to the number of moles of solute added. This property, known as freezing-point depression, is a colligativeproperty; that is, it depends on the ratio of solute and solvent particles, not on the nature of the substance itself. The equation that shows this relationship ist= Kfwheretis the freezing point depression, Kfis the freezing point depression constant for a particular solvent (3.9°Ckg/mol for lauric acid in this experiment1) and mis the molality of the solution (in mol solute/kg solvent).OBJECTIVESIn this experiment, you willDetermine the freezing temperature of the pure solvent, lauric acid.Determine the freezing temperature of a mixture of lauric acid and benzoic acid.Calculate the freezing point depression of the mixture.Calculate the molecular weight of benzoic acid. m Figure 1 MATERIALS LabQuest lauric acid, CH 3 (CH 2 ) 10 COOH LabQuest App lauric acid-benzoic acid mixture Temperature Probe hot water bath two 18 150 mm test tubes utility clamp 400 mL beaker paper towel or tissue ring stand
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