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Determining the Molar Mass of a Volatile GasAP Chemistry4th hour28 September 2017Purpose:
The purpose of this experiment was to determine the molecular mass of an unknown, volatile gasby measuring vapor density and to verify the derived formula MM=¿DRTP.Pre Lab: If the volume of a 0.125 g sample of gas at 735 mm Hg and 45 is 60.2 mL, what is the ℃molecular mass of this compound?MM=¿DRTPD=mv¿(2.08g/L)(.08206)(318K)(.967atm)¿.125g.0602L¿56.0g/mol¿2.08g/LProcedure:1.Turn on a hot plate and bring about 1 L of water to a boil. 2.Obtain a piece of aluminum foil and a small rubber band. 3.Cover the top of a clean, dry 125 mL Erlenmeyer flask with the foil and secure it with therubber band. Cut off the excess aluminum foil (the rubber band should still be holding the foil all the way around the neck of the flask), so that the surface area is minimal. 4.Use a needle to poke a small hole in the center of the foil. Make sure the hole goes all theway through the foil. 5.Mass the flask (with the foil and rubber band) to ± 0.001 g. Tare the balance and use the same balance for all measurements. 6.Use a graduated cylinder to measure about 6 mL of the unknown liquid (#1). Take the aluminum foil off the flask and pour the liquid in. Replace the foil and rubber band.7.Use tongs to hold the Erlenmeyer flask in the boiling water, making sure the foil and the top of the flask remain dry. About half an inch of the bottom of the flask should be in the water. 8.When all of the liquid in the flask has evaporated, start a timer and continue boiling for three minutes. 9.After three minutes, record the temperature of the water to the nearest ± 0.1(assume ℃that the vapor inside the flask is the same temperature as the water). 10. Record barometric pressure. 11. Remove the flask from the boiling water and put it on a paper towel to cool. Then dry theoutside of the flask. Make sure that no water has condensed under the foil, but do not remove the foil from the mouth of the flask.