16 To determine the freezing point of the benzoic acid lauric acid solution you

16 to determine the freezing point of the benzoic

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16. To determine the freezing point of the benzoic acid-lauric acid solution, you need to determine the temperature at which the mixture first started to freeze. Unlike pure lauric acid, cooling a mixture of benzoic acid and lauric acid results in a slow gradual drop in temperature during the time period when freezing takes place. Graph Time Freezing Point
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17.A good way to compare the freezing curves of the pure substance and the mixture is to view both sets of data on one graph. Prepare a graph that contains both the line of the pure lauric acid and the lauric acid-benzoic acid solution. PROCESSING THE DATA 1.Determine the difference in freezing temperatures, t,between the pure lauric acid (t1) and the mixture of lauric acid and benzoic acid (t2). Use the formula, t= t1t2.Calculate molality (m), in mol/kg, using the formula, t= Kfm(Kf= 3.9°C-kg/mol for lauric acid).3.Calculate moles of benzoic acid solute, using the answer in Step 2 (in mol/kg) and the mass (in kg) of lauric acid solvent.4.Calculate the experimentalmolecular weight of benzoic acid, in g/mol. Use the original mass of benzoic acid from the Data and Calculations table, and the moles of benzoic acid you found in the previous step.5.Determine the acceptedmolecular weight for benzoic acid from its formula, C6H5COOH.6.Calculate the percent error. 2 . DATA AND CALCULATIONS Mass of lauric acid g Mass of benzoic acid g Freezing temperature of pure lauric acid °C Freezing point of the benzoic acid–lauric acid mixture °C Freezing temperature depression, t °C Molality, m mol/kg Moles of benzoic acid mol Molecular weight of benzoic acid (experimental) g/mol Molecular weight of benzoic acid (accepted) g/mol Percent error
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  • Freezing-point depression, Lauric acid

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