EXPERIMENT 1 - MAPUAINSTITUTEOFTECHNOLOGY

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MAPUA INSTITUTE OF TECHNOLOGY School of Chemical Engineering and Chemistry CHM170L / B41 / Group No. 6 Experiment No. 1 DETERMINATION OF MOLAR MASS OF A VOLATILE LIQUID BY VAPOR- DENSITY METHOD TAN, Aieocellis F. TANGARA, Neil Patrick P. VELASCO, Christel Charmaine D. VILLAFLOR, Arthur C. ABSTRACT This experiment intends to estimate the molar mass of volatile liquids from their vapor densities at a temperature above their boiling points using the Dumas Method. The Dumas method is one of the simplest ways to measure the molecular weight of a substance and uses the ideal gas law. The temperature and the mass of the gas sample are measured, along with the atmospheric pressure. Since liquids are much easier to handle than gases, a volatile liquid is usually used as the source of the gas. The liquid must have a boiling point substantially above room temperature and below the boiling point of water. Three volatile reagents; ethyl acetate, acetone and ethyl alcohol were exploited. The main step in determining the molecular mass is to inject small amount of volatile liquid into the foil – covered flask through a tiny opening and to heat in a boiling water bath to vaporize the liquid. When all of the liquid is vaporized and no more vapor is seen leaving the bulb, the bulb contains a sample of vapor at atmospheric pressure and 100 ºC with a volume exactly equal to the volume of the bulb. The data needed to obtain the molecular mass of the volatile liquids are: pressure (P), volume, (V) the mass of the vapor, (g), and the temperature (T) by following the procedures. After the prolonged calculations, the gathered percentage difference for ethyl acetate, acetone and ethyl alcohol is 45.69%, 8.36% and 42.33%, respectively.
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MAPUA INSTITUTE OF TECHNOLOGY School of Chemical Engineering and Chemistry CHM170L / B41 / Group No. 6 Introduction The objective of this experiment is to estimate the molar mass of volatile liquids from their vapor densities at temperature above their boiling point using the Dumas method. In the Dumas’ method a volatile liquid is heated to a known temperature and allowed to escape from a container through a tiny hole. 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. Methodology The experiment consists of creating a container with a reproducible volume and a pinhole orifice from which the volatile liquid shall be vaporized at the boiling point water and at room pressure. After cooling, the mass of the container is greater by the amount of liquid that remains (representing the amount of vapour which filled the volume at the boiling point of water and at room pressure). A mass correction must also
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EXPERIMENT 1 - MAPUAINSTITUTEOFTECHNOLOGY

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