DATA TABLE Mass of lauric acid (g) Mass of benzoic acid (g) Tial 2 15 7.85 7.92

Question

DATA TABLE Mass of lauric acid (g) Mass of benzoic acid (g) Tial 2 15 7.85 7.92 Freezing temperature of pure luric acid (c) 42.8° c 42.C 42 8 C Freezing point of benzoic acid launc acid mixture (c) |31.65c 31c 3471 DATA ANALYSIS 1. Calculate molality (m), in mol/kg, using the formula Ar Kx m for each of your trials. The Kyvalue for lauric acid is 3.9 C-kg/mol. 2. Calculate moles of benzoic acid solute, using the molality and the mass (in kg) of lauric acid solvent for each of your trials 3.Calculate the experimental molecular weight of benzoic acid, in g/mol for each of your trials. 4.Determine the average experimental molecular weight of benzoic acid. 5.Determine the standard deviation for your experimental molecular weight of benzoic acid for your esprimental molecular

Explanation / Answer

1. Change in freezing point = Freezing point of pure lauric acid - freezing point of lauric acid - benzoic acid mixture .

For trial 1 :

Change in freezing point = t= 42.8-36.5 = 6.3

As kf = 3.9°CKg/mol

Then , m=t/kf=6.3/3.9=1.615 mol/kg.

For trial 2 :

Change in freezing point =t=42.8-37.7=5.1

As kf=3.9°Ckg/mol

Then m=t/kf=5.1/3.9=1.307mol/kg.

For trial 3 :

Change in freezing point =t=42.8-34.77=8.03

As m=3.9°Ckg/mol

Then m=t/kf= 8.03/3.9=2.058mol/kg.

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