Vapor Lab

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Enthalpy of vaporization of ethanol was determined by measuring change in temperature and pressure of ethanol using a Vernier temperature probe. By using the ideal gas equation, and plugging the slope value from the graph into the Clausius-Claypernon equation, enthalpy of vaporization was determined to be 10kJ/mol. The percent error was determined to be 76.0%. Introduction:

The purpose of this lab is to investigate vapor pressures and the partial pressure of gas produced from liquids at different temperatures. These pressures vary at different temperatures. In any given liquid there is a vapor that is produced above directly above the liquid, this can be determined intuitively from smell. (Do not smell the liquid used in this experiment, denatured alcohol is harmful) At a given temperature the evaporation and condensation happen at the same rate which causes an equilibrium called vapor pressure. In this experiment only the total pressure within a sealed container can be determined, which is done so by using a Vernier temperature probe. Increase in pressure is determined using the probe to calculate pressure with increased temperature. To calculate increase in pressure of the air, the ideal gas law is used which is: PV=nRT

Where P = Pressure V = Volume n = number of moles R = ideal gas constant and T = temperature. The rest of the total pressure increase measured will be determined from the vapor pressure of the ethanol. The dependence of vapor pressure on temperature is shown by the Clausius-Claypernon equation which is: lnP2P1=-∆HvapR[1T2-1T1]

By plotting the data Pressure vs Temperature, it is discovered that the data is not linear. Plotting the data as lnP vs 1/T will give a linear graph. Using the slope of this line will show the enthalpy of vaporization. This enthalpy can be used to determine the vapor pressure of ethanol at any range of temperatures.

Table 1: Data table shows information conducted from 5 trials for...
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