Vapor Pressure Lab

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Natasha Jivani
The Vapor Pressure of Water
February 11,2012
Dr. Asmerom Hagos
Lab Group Members: Stephany

Observe a glass of water that is left in an open container at room temperature. It will eventually evaporate completely, even though its temperature is never raised to the boiling point. The explanation for this behavior is that some of the molecules in the liquid have enough kinetic energy to overcome the intermolecular forces, which hold the molecules of the liquid together, and are able to escape into the vapor phase. The molecules in the vapor phase then diffuse away, and a net loss of liquid occurs. The vapor pressure of a liquid depends upon the molecular structure of the liquid and its temperature. Increasing the temperature increases the average kinetic energy of the liquid molecules, and hence the fraction of molecules with sufficient energy to escape from the liquid phase. Thus, the vapor pressure increases with temperature. The objective of this experiment is to experimentally determine the enthalpy of vaporization of water. Procedure

1. Obtain a 10mL graduated cylinder and a large beaker.
2. Fill the beaker with distilled water.
3. Put enough distilled water in the graduated cylinder to fill the cylinder to 90% capacity. 4. Place finger over the mouth of the graduated cylinder and invert the cylinder in the beaker 5. An air bubble of 4 to 5mL should remain in the cylinder 6. Add distilled water until the graduated cylinder is covered completely 7. Heat the beaker to 75 to 80 degrees Celsius.

8. Once the temperature is reached, remove the beaker from heat and start recording the volume of the bubble and the temperature of the water 9. Take readings every 5 degrees until water temperature has cooled to 45 degrees Celsius. 10. Then add ice to the beaker to lower the temp to below 5 degrees Celsius and record the volume of the air bubble. 11. Record the value of...
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