01MANPTgasVPliquidLE - Temperatures Relationship to Gas &...

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Temperature’s Relationship to Gas & Vapor Pressure Revised 1/22/10 1 TEMPERATURE’S RELATIONSHIP TO GAS & VAPOR PRESSURE Adapted from "Chemistry with Computers" Vernier Software, Portland OR, 1997 OBJECTIVES Data will be collected to determine the relationship between gas pressure and temperature and to find absolute zero. Using the same experimental setup the relationship between vapor pressure and temperature will be determined. Furthermore, a plot of the natural log of vapor pressure versus inverse Kelvin will permit the calculation of the heat of vaporization ( H vap ) from the Clausius Clapeyron equation: ln P = (– H vap / R) (1/T) + C. SAFETY Students must wear safety goggles and lab aprons at all times in the lab. Be careful when handling heated glassware. Use paper towels, toweling, or tongs to avoid burns. Ethanol is flammable; make sure there are no sparks or flames in lab. Ethanol fumes can irritate eyes and lungs; avoid contact with fumes. INTRODUCTION Molecules in the gas phase are in constant motion. Gas pressure is a measurement of the number of collisions of molecules with the walls of the container. The velocity and the number of collisions of these molecules changes when the temperature of the gas increases or decreases. In this experiment, the relationship between the temperature of a gas sample and the pressure it exerts will be investigated. Using the apparatus shown in Figure 1, an Erlenmeyer flask containing an air sample will be placed in water baths of varying temperature.
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Temperature’s Relationship to Gas & Vapor Pressure Revised 1/22/10 2 Figure 1 Pressure will be monitored with a pressure sensor and temperature will be monitored using a temperature probe. The volume of the gas sample and the number of molecules it contains must be kept constant. Pressure and temperature data pairs will be collected during the experiment and then analyzed. From the data and graph, you will determine what kind of mathematical relationship exists between the pressure and absolute temperature of a confined gas. Finally, the value for absolute zero will be determined. In the next part of this experiment you will investigate the relationship between vapor pressure and temperature and find the heat of vaporization ( H vap ) of ethanol. When a liquid is added by syringe to the same sealed Erlenmeyer flask used for the first part of the experiment (Figure 2), it will begin to evaporate into the air above in the flask. Figure 2 Evaporation will continue until equilibrium is established between the rate of evaporation and the rate of condensation. At this point, the vapor pressure of the liquid is equal to the partial pressure of its vapor in the flask. The pressure sensor will be used to measure changes in the total pressure in the flask (the pressure resulting from air and gaseous ethanol molecules together).
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Temperature’s Relationship to Gas & Vapor Pressure Revised 1/22/10 3 First, the pressure in the flask will be measured at room temperature and then the flask will be
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This note was uploaded on 11/18/2010 for the course CHEMISTRY Chem 1LE taught by Professor Dr.kimberlyedwards during the Spring '10 term at UC Irvine.

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01MANPTgasVPliquidLE - Temperatures Relationship to Gas &...

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