Determining Molar Mass by Ideal Gas Law Essay

907 Words Jan 6th, 2012 4 Pages
I. Abstract:

By manipulating the ideal gas law (PV=nRT), we will be determining the molar mass of an unknown volatile liquid. Heating a flask filled with an unknown, easily evaporated liquid will allow for measurements that can be taken to work out the ideal gas equation. This lab will require knowledge of basic equations used in chemistry. Using these equations, such as density and number of moles(n), we can substitute different values into the ideal gas law to manipulate it.

II. Materials: 250-mL Erlenmeyer flask Needle or pin Unknown liquid sample Barometer 1000-mL beaker Hot plate Utility clamp Aluminum freezer foil
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Measure and record the exact temperature of the boiling water in the beaker, as well as the barometric pressure in the lab. 12. When the flask has cooled completely, carefully dry the outside of the flask to remove any water. Weigh the flask, foil cover, and vapor with as many sigfigs as possible. 13. Perform a second trial, if the final mass of the flask and vapor is not within 0.05g of the first trial, perform a 3rd. 14. When two acceptable trials have been performed, remove the foil cover and clean the flask. 15. Fill the flask to the very rim with water and pour it into a 1000-mL graduated cylinder to determine the exact volume of the flask. Record.

IV. Data and Observations

| |TRIAL 1 |TRIAL 2 |
|BAROMETRIC PRESSURE (mm Hg) |763.5 mm Hg |763.5 mm Hg |
|MASS OF FLASK AND FOIL COVER (g) |106.095g |106.095g |
|TEMPERATURE OF WATER IN BEAKER (°C) and |99.1°C / 372.1 K |97.9°C / 370.9 K |
|(K) | | |
|MASS OF FLASK/COVER AND CONDENSED LIQUID |106.406g

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