CHEM 121 General Chemistry Laboratory Freezing-Point Depression

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Using Freezing-Point Depression to Find Molecular Weight OBJECTIVES  Determine 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. MATERIALS  Vernier computer interface  Computer  Logger Pro  Temperature Probe  Stir Station  400 mL beaker  Tissue or paper towels  Lauric acid, CH3(CH2)10COOH  Lauric acid-benzoic acid mixture  Hot water bath  Two 18 × 150 mm test tubes  Utility clamp INTRODUCTION When 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 colligative property; 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 is ΔT = -i Kf × m [Show More]

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