Chemistry Practice Problems The Colligative Properties Practice Problems Solution: Using freezing point depression to find molecular ...

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Solution: Using freezing point depression to find molecular weightMass of Lauric Acid (g)                                                                     8.003Mass of benzoic Acid (g)                                                                   1.010Freezing temperature of pure lauric acid (C°)                                   43.84Freezing temperature of the benzoic acid-lauric acid mixture (C°)   39.05a. Calculate molality (m), in mol/kg, using the formula Δt = Kf  * m. The Kf value for lauric acid is 3.9°C•kg/mol. b. Calculate moles of benzoic acid solute, using the molality and the mass (in kg) of lauric acid solvent.  c. Calculate the experimental molecular weight of benzoic acid, in g/mol.  d. Determine the accepted molecular weight of benzoic acid from its formula, C 6H5COOH. e. Calculate the percent discrepancy between the experimental and accepted values.   

Problem

Using freezing point depression to find molecular weight

Mass of Lauric Acid (g)                                                                     8.003

Mass of benzoic Acid (g)                                                                   1.010

Freezing temperature of pure lauric acid (C°)                                   43.84

Freezing temperature of the benzoic acid-lauric acid mixture (C°)   39.05

a. Calculate molality (m), in mol/kg, using the formula Δt = K * m. The Kf value for lauric acid is 3.9°C•kg/mol.

 

b. Calculate moles of benzoic acid solute, using the molality and the mass (in kg) of lauric acid solvent.

 

 

c. Calculate the experimental molecular weight of benzoic acid, in g/mol.

 

 

d. Determine the accepted molecular weight of benzoic acid from its formula, C 6H5COOH.

 

e. Calculate the percent discrepancy between the experimental and accepted values.