Determining Molar Mass by Ideal Gas Law

I. Abstract By manipulating the ideal plash rightfulness (PV=nRT), we will be determining the hero mass of an alien volatile mobile. Heating a flaskfulful filled with an unknown, easily e vaporated smooth will allow for measurements that can be taken to work verboten the ideal gas equation. This laboratory will require knowledge of sanctioned equations employd in chemistry. Using these equations, such as density and tour 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 liquefiable sampleBarometer 1000-mL beaker Hot plate Utility clamp Aluminum deep-freeze go bad Hot mitt Wire gauze with ceramic stub 1000-mL graduated cylinder III. Procedure 1. Aprons and goggles on. Clean a 1000-mL beaker for use as a heating bath. Set the beaker on a glowing plate and begin heating. 2. Clean and completely dry the Erlenmeyer flask. 3. Cut a squ ar of aluminum foil to serve as the over fly of the flask. push down the edges so that it neatly covers the edge of the flask. 4. bid the empty flask with cover and record to as many sigfigs as possible. 5.Obtain your unknown molten and record the ID . Add 3-4 mL of the liquid to the flask. Re-cover the flask, making sure the edges are tightly c brinkped. 6. Punch a tiny hole in the foil cover with a needle or pin. 7. Heat the water in the beaker to change state. Adjust the heat so that the water will remain boiling but will non splash. 8. Immerse the flask containing the unknown liquid in the boiling water so that most of the flask is covered. clamp the neck of the flask. 9. Watch the liquid carefully. The liquid will begin to evaporate, and its muckle will decrease. 10.When it appears that the flask is completely filled with vapor, continue heating for 1-2 minutes. discharge the flask from the bath using the clamp. 11. Set the flask on the wire gauze on the lab table, ask out the clamp, and allow the flask to sedate to room temperature. Measure and record the ingest 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. 3. Perform a second tryout, if the final mass of the flask and vapor is not at bottom 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 barometrical PRESSURE (mm Hg) 763. mm Hg 763. 5 mm Hg draw OF FLASK AND FOIL COVER (g) 106. 095g 106. 095g TEMPERATURE OF WATER IN BEAKER (C) and 99. 1C / 372. 1 K 97. 9C / 370. 9 K (K) vision OF FLASK/COVER AND CONDENSED LIQUID 106. 406g 106. 8 7g (g) Volume of Erlenmeyer Flask (determined by picking completely with water) 289mL Unknown liquid ID B (ethyl alcohol) V. Analysis of Data PV = nRT running game 1) 763. 5 (. 289 L) = n (62. 4) (372. 1) 220. 6515 = 23219. 04 n 220. 6515/23219. 04 = n 0. 0095 mol = n multitude of vapor in the flask = (mass of flask/cover and condensed liquid) (mass of empty flask/cover) commode of vapor in the flask = 106. 406g 106. 095g = 0. 311g 0. 311g/0. 0095 mol = 32. 73 g/mol = molar mass Trial 2) 763. 5 (. 289 L) = n (62. 4) (370. 1) 220. 6515 = 23094. 24 n 220. 6515/23094. 24 = n 0. 0096 mol = n Mass of vapor in the flask = (mass of flask/cover and condensed liquid) (mass of empty flask/cover) Mass of vapor in the flask = 106. 487g 106. 095g = 0. 392g 0. 392g/0. 0096 mol = 41. 02 g/mol = molar mass AVERAGE MOLAR MASS (32. 3 + 41. 02) / 2 = 36. 875 g/mol Theoretical molar mass of ethyl alcohol 46. 07 g/mol VI. Conclusion (36. 875 46. 07) / 46. 07 (x 100) = 19. 9% = pe rcent error The first trial was very unsuccessful while the second trial was much proximate to the theoretical value. The possibilities of error within the first trial include not letting the flask cool completely to room temperature before weighing and also forgetting to utilize acetone to dry the flask before the do-gooder of the liquid. The latter was the major difference in performance of the two trials.This taste showed that the interference of water vapor can completely wreck the lay on the line for an accurate measurement of volume of a different gas. It is imperative to guide sure that the flask is as dry as possible or the results will show a very wrong answer. It is hard to regard the prominence of water vapor in the air until an experiment the like this one shows that it takes up a relatively huge space in a given volume of air. A suggestion to improve this lab could be to place more emphasis on drying the flask with a paper towel and acetone before use.