Freezing point depression lab
Using Freezing-Point Depression to Find Molecular Weight
Abstract: In this lab, the purpose was to use the freezing point depression method to determine the molecular weight of aspirin. This was done by determining the freezing of t-butanol and that of a t-butanol and aspirin solution; then finding the molality of the solution, and moles of aspirin. In the results of the experiment, the molar mass was found to be 192.2 g/mol, which differed from the established value of 180.2 g/mol by 6.7% error.
Introduction:
Freezing point depression defined as a vertical medium in reference to boiling point elevation. The general definition is the effect of lowering the freezing point of a substance due to an increased amount of solute added to the solvent. This effect is known as colligative property. The equation that shows this relationship is: ΔT= Kf * m Eq. 1 The goal of this experiment was to determine the molar mass of aspirin using the freezing point depression method. First, the freezing temperature of the pure solvent and t-butanol were determined. Then by adding a known mass of aspirin to a known mass of t-butanol, the lowering of the freezing temperature of the solution was determined. By measuring the freezing point depression, ΔT, and the mass of aspirin, the molar mass of the aspirin solute was determined.
Equations used in this experiment:
The different in freezing temperatures between t-butanol and mixture of t-butanol and aspirin: ΔT= T1- T2 Eq. 2 Where T1: temperature of t-butanol T2: temperature of t-butanol and aspirin
The molar mass of aspirin: Moles= mass/ molar mass Eq. 3
Data:
Table 1. Mass of all the measurements (g)
Trial 1 Trial 2
Mass of test tube (g) 18.32 18.32
Mass of test tube+ t-butanol (g) 20.548 20.409
Mass of aspirin+ solvent+ test tube (g) 20.504 20.670
Results:
Table 2. Freezing temperature of t-butanol and aspirin-butanol solution (°C)
Trial 1 Trial 2
Abstract: In this lab, the purpose was to use the freezing point depression method to determine the molecular weight of aspirin. This was done by determining the freezing of t-butanol and that of a t-butanol and aspirin solution; then finding the molality of the solution, and moles of aspirin. In the results of the experiment, the molar mass was found to be 192.2 g/mol, which differed from the established value of 180.2 g/mol by 6.7% error.
Introduction:
Freezing point depression defined as a vertical medium in reference to boiling point elevation. The general definition is the effect of lowering the freezing point of a substance due to an increased amount of solute added to the solvent. This effect is known as colligative property. The equation that shows this relationship is: ΔT= Kf * m Eq. 1 The goal of this experiment was to determine the molar mass of aspirin using the freezing point depression method. First, the freezing temperature of the pure solvent and t-butanol were determined. Then by adding a known mass of aspirin to a known mass of t-butanol, the lowering of the freezing temperature of the solution was determined. By measuring the freezing point depression, ΔT, and the mass of aspirin, the molar mass of the aspirin solute was determined.
Equations used in this experiment:
The different in freezing temperatures between t-butanol and mixture of t-butanol and aspirin: ΔT= T1- T2 Eq. 2 Where T1: temperature of t-butanol T2: temperature of t-butanol and aspirin
The molar mass of aspirin: Moles= mass/ molar mass Eq. 3
Data:
Table 1. Mass of all the measurements (g)
Trial 1 Trial 2
Mass of test tube (g) 18.32 18.32
Mass of test tube+ t-butanol (g) 20.548 20.409
Mass of aspirin+ solvent+ test tube (g) 20.504 20.670
Results:
Table 2. Freezing temperature of t-butanol and aspirin-butanol solution (°C)
Trial 1 Trial 2