Dumas Method Essay

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Due Date: February, 4th 2013 AP Chemistry – Lab #4 Part 1: Molecular Mass of a Volatile Liquid – Dumas Method PV = nRT OBJECTIVE The main purpose of performing this experiment is to determine the molecular weight of an unknown substance using the Dumas Method. A volatile liquid will be confined in a container and boiled. With this method’s use of the ideal gas law we will need to find pressure, volume, mass of the vapor that’s escaping the flask, and the temperature. If all is executed correctly, percent error should not exceed 10%. SAFETY * Wear goggles at ALL TIMES * Be careful not to ingest any chemicals * Handle boiling water with care * If any chemical should come in contact with your skin rinse IMMEDIATELY * Report any and all accidents to your teacher/advisor PROCEDURE 1. Attach a utility clamp to a 125mL Erlenmeyer flask. Submerge the flask as deep as possible into a 600mL beaker on a hot plate. Pour water into the beaker around the outside of the flask; be sure to allow enough splash area for the boiling water so it does not fly out of the beaker and onto you. MAKE SURE NO WATER GOES INSIDE THE FLASK. Heat the water to boiling. As you are waiting for the water to boil, remove the flask from its clamp and dry it. 2. Cut a small square piece of aluminum foil and place it over the flask. Fold the foil on its mouth and pull its corners around the flask’s neck. Secure it with a rubber band. Make a hole on the tin foil with a pin and make sure it’s completely open. 3. Weigh flask, foil cap and rubber band to the nearest milligram and record the mass. 4. Obtain a sample of unknown liquid. Add about 2mL to the flask (be sure to remove the foil cap). Replace both foil and rubber band. Clamp the flask onto the ring stand and submerge the water again. 5. Measure the temp of the boiling water and

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