The formula we use to calculate the change in freezing point of a liquid with a solute is shown here: AT = i Kf m [1] where AT is the change in temperature from the freezing point of the pure liquid, i is the van't Hoff factor, Kf is the freezing point constant for that particular liquid, and m is the concentration in molality (moles of solute per kilogram of solvent). In this lab you will determine the molecular weight of an unknown compound by introducing a known mass of the compound to tert-butanol and measuring the change in the freezing point of the solution. From this change, you can calculate the molality of the solute in the solution and knowing the mass of compound you introduced, you can calculate the molecular weight of the unknown compound.
The formula we use to calculate the change in freezing point of a liquid with a solute is shown here: AT = i Kf m [1] where AT is the change in temperature from the freezing point of the pure liquid, i is the van't Hoff factor, Kf is the freezing point constant for that particular liquid, and m is the concentration in molality (moles of solute per kilogram of solvent). In this lab you will determine the molecular weight of an unknown compound by introducing a known mass of the compound to tert-butanol and measuring the change in the freezing point of the solution. From this change, you can calculate the molality of the solute in the solution and knowing the mass of compound you introduced, you can calculate the molecular weight of the unknown compound.
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Rearrange equation 1 to solve for the molecular weight of a compound assuming you know the mass of solute added
![Lab 1 - Freezing Point Depression
Objectives:
●
Fall 2021- Spring 2022
Students will use their understanding of colligative properties to determine the physical
properties of an unknown substance.
Introduction
Colligative properties refer to properties of solutions which depend only on the
concentration of solute particles in solution, not on their identity. Four colligative properties
which you will be discussing in class are freezing point depression, boiling point elevation, vapor
pressure lowering, and osmotic pressure. According to these properties, as solute concentration
increases, the freezing point of the total solution (relative to the original pure solvent) occurs at
a lower temperature, the boiling point occurs at a higher temperature, the vapor pressure (partial
pressure of the vapor above the surface of the liquid) is lower, and osmotic pressure increases.
These deviations are due to changes in the total influence of intermolecular forces caused by the
presence of a solute.
The formula we use to calculate the change in freezing point of a liquid with a solute is
shown here:
AT = i Kf m
where AT is the change in temperature from the freezing point of the pure liquid, i is the van't
Hoff factor, Kis the freezing point constant for that particular liquid, and m is the concentration
in molality (moles of solute per kilogram of solvent). In this lab you will determine the molecular
weight of an unknown compound by introducing a known mass of the compound to tert-butanol
and measuring the change in the freezing point of the solution. From this change, you can
calculate the molality of the solute in the solution and knowing the mass of compound you
introduced, you can calculate the molecular weight of the unknown compound.
[1]](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc7cfbf0b-4345-4268-a259-634bcd51c9b5%2F8bcc703b-89e6-4778-8e4f-5b47d8833f5b%2F2bgcfc_processed.jpeg&w=3840&q=75)
Transcribed Image Text:Lab 1 - Freezing Point Depression
Objectives:
●
Fall 2021- Spring 2022
Students will use their understanding of colligative properties to determine the physical
properties of an unknown substance.
Introduction
Colligative properties refer to properties of solutions which depend only on the
concentration of solute particles in solution, not on their identity. Four colligative properties
which you will be discussing in class are freezing point depression, boiling point elevation, vapor
pressure lowering, and osmotic pressure. According to these properties, as solute concentration
increases, the freezing point of the total solution (relative to the original pure solvent) occurs at
a lower temperature, the boiling point occurs at a higher temperature, the vapor pressure (partial
pressure of the vapor above the surface of the liquid) is lower, and osmotic pressure increases.
These deviations are due to changes in the total influence of intermolecular forces caused by the
presence of a solute.
The formula we use to calculate the change in freezing point of a liquid with a solute is
shown here:
AT = i Kf m
where AT is the change in temperature from the freezing point of the pure liquid, i is the van't
Hoff factor, Kis the freezing point constant for that particular liquid, and m is the concentration
in molality (moles of solute per kilogram of solvent). In this lab you will determine the molecular
weight of an unknown compound by introducing a known mass of the compound to tert-butanol
and measuring the change in the freezing point of the solution. From this change, you can
calculate the molality of the solute in the solution and knowing the mass of compound you
introduced, you can calculate the molecular weight of the unknown compound.
[1]
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