The total pressure of the bubble will remain at the

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The total pressure of the bubble will remain at the room pressure, since it is determined by the room air pushing down on the surface of the water in the beaker. So for all temperatures, p air + p water = P room (5)
Once you have determined the number of moles of air present from your low temperature data where p water is negligible, you can determine the partial pressure of air at each temperature using the ideal gas law ࠵? ࠵?࠵?࠵? = ࠵? ࠵?࠵?࠵? ࠵?࠵? ࠵? (6) for each temperature using eqn 7. You can then calculate p water at each temperature. Then, using eqn 2 and plotting ln(p water ) as a function of 1/T, you can determine D H o vap . There is a small systematic error because you are using the graduated cylinder in an inverted position. This reverses the shape of the air/water meniscus. To correct for this error, you will subtract 0.2 ml from all your volume readings. This is an experimental value, so it will affect the number of significant figures of your corrected volumes. As in all experiments, the raw data should still be recorded in your notebook. You will correct the raw data in the results section of your assignment and use the corrected data in your calculations. Objectives This experiment is designed to help you connect some of the more abstract concepts of equilibrium and thermodynamics with laboratory observations. From this experiment, you should be able to Observe the effect of temperature on water vapor from the effect it has on a bubble composed of air and water vapor. o This requires the understanding of Dalton’s law of partial pressure. o This also requires an understanding of the ideal gas law. Use the liquid/vapor equilibrium generated in the bubble to determine an enthalpy of vaporization of water, making the connection between equilibrium and thermodynamics. Give reasons for some of the laboratory procedures in this experiment. Connect the procedures and your observations to errors and uncertainties in your results. S AFETY Bunsen burners pose a fire risk. Before you start, clear all books and papers away from your work area. Tie your hair back and roll up loose sleeves. Check that the hose on your Bunsen burner is not stiff or cracked. Replace it if necessary. You must wear chemical splash goggles and closed toed shoes. Wear a shirt that covers your upper chest and shoulders. Gloves and apron will be provided. P ROCEDURE Obtain an Experiment Bucket from the stockroom. Fill the beaker to ~800 ml with DI water. Fill the graduated cylinder until it is about 2/3 full to the top of the cylinder.

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