CHM170L expt 1 - MAPUAINSTITUTEOFTECHNOLOGY

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MAPUA INSTITUTE OF TECHNOLOGY School of Chemical Engineering, Chemistry and Biotechnology P h y s i c a l   C h e m i s t r y   L a b o r a t o r y   1 Experiment 1 Determination of Molar Mass of a Volatile Liquid  by Vapor-Density Method Section: A31 Group No.4: Date Performed:  April 24, 2007 Members: Date Submitted:   May 5, 2007 Javier, Sandra        Ko, Denniel Gaviola, Catherine Gososo, Shelamae Olivete, Jasper Ryan Abstract The classic Dumas method has been used to determine the molar mass  of volatile liquids from their vapour densities at a temperature above their boiling  points.   The   values   obtained,   with   17.50%   average   difference,   are   64.3893   for   acetone, 62.7415 for ethanol and 98.9198 for ethyl acetate.  The literature values  were 58.08 for Acetone, 46.07 for ethyl Alcohol and 88.16 for ethyl acetate. Using the Dumas Method, the aluminum foil was used to trap the liquid   upon boiling until the liquid evaporates. Our values were quite far from the original  molar masses of the compounds. The percentage difference was raging from 10-30 
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%. The possible causes of error were upon the weighing of the sample and the  pinhole that was used to transfer the volatile liquid to the flask. I. Introduction The objective of this experiment is to estimate the molar mass of volatile  liquids by means of Dumas’ method. The knowledge on various gas laws allows the  application of this method to liquids and solids which are volatile. With a given  temperature and volume, a measured volume of gas can be converted to moles  given that PV=nRT In the Dumas’ method a volatile liquid is heated to a known temperature  and allowed to escape from a container through a tiny orifice. Once the liquid has  vaporized, the container is cooled to room temperature. The vapor which remained  in the container at the higher temperature gradually condenses to a liquid and is  then   massed.   Knowing   the   volume   of   the   container   together   with   the   high  temperature, the room pressure can be used to calculate moles. From there a molar  mass can be determined. II. Methodology The materials used are the following: 250mL Erlenmeyer flask beaker iron stand bunsen burner copper wire clamp foil syringe (1)
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thermometer barometer analytical balance The Reagents used are the following: Acetone  (CH 3 COCH 3 )-   is a colorless, mobile, flammable liquid with melting point of  −95.4 °C and boiling point of 56.53 °C. It has a relative density of 0.819 (at 0 °C). It  is readily soluble in  water,  ethanol,  ether, etc., and itself serves as an important  solvent.
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This note was uploaded on 07/31/2011 for the course CHE-CHM-BT CHM170L taught by Professor Maynardaustria during the Spring '11 term at Mapúa Institute of Technology.

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CHM170L expt 1 - MAPUAINSTITUTEOFTECHNOLOGY

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