3 Separation of Liquids by Simple Distillation

3 Separation of Liquids by Simple Distillation - Separation...

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Separation of Liquids by Simple Distillation. Analysis of Separation Efficacy by Construction a Volume vs. Temperatures Graph and Analyzing Distillates by Gas- Liquid Chromatography. James Mendoza February 18, 2008 Methods and Background The purpose of this lab is to successfully distill a solution of ethyl acetate and butyl acetate, and take a gas-liquid chromatography of three different fractions of the distilled solution at different temperatures. From the distillation, an analysis of the volume of distilled liquid compared to the temperature of the liquid can be recorded. Ethyl Acetate Butyl Acetate Given a system with a liquid in a container, the rate at which molecules in the gas phase reenter the liquid will eventually become equal to the rate at which they escape from the liquid, resulting in a dynamic equilibrium. The molecules in the gas phase will collide with the walls of the container, producing pressure referred to as the equilibrium vapor pressure, which varies directly with temperature. When the equilibrium vapor pressure equals the atmospheric pressure (760 Torr or 1 atm), the rate of evaporation of the liquid increases significantly and bubbles are formed. When this occurs, its boiling point has been reached. When considering mixtures of liquids, Raoult’s law is used to determine the partial pressure of each liquid. It states that the partial pressure is equal to the product of the equilibrium vapor pressure and the mole fraction. Dalton’s law of partial pressures then dictates that the partial pressures of the liquids must sum up to the total pressure of the liquid. Boiling points are affected by intermolecular forces; molecules with greater attractive forces have higher boiling points because it takes more energy to break the bonds between the molecules. Although ethyl acetate (EtOAc) and butyl acetate (BuOAc) have similar polarities due to the presence of ester functional groups, butyl acetate is a larger, more massive molecule As a result, the Van der Waals forces between its molecules will be greater, leading to stronger intermolecular bonds and a higher boiling point. Simple distillation is used to separate a mixture of components through condensation and their differences in volatility. Distillation separates distillates from less- volatile substances by first vaporizing liquids through boiling and then condensing them. It is specifically used when separating liquids that differ in boiling points by more than 40-50 °C. Since the more volatile liquid in a mixture has a higher equilibrium vapor pressure and thus a higher partial pressure, the vapor of the mixture of liquids contains a greater proportion of the components of the more volatile liquid. As the vapor
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This note was uploaded on 04/07/2008 for the course CH 233 taught by Professor Landrie during the Spring '08 term at Ill. Chicago.

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3 Separation of Liquids by Simple Distillation - Separation...

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