To determine the molar mass of a volatile liquid, we used the Dumas method with a test tube, tin foil cover, and hot water bath to convert the liquid to a gas and then measure its pressure, temperature, amount, and volume.

a) Why must you leave the test tube in the hot water for several minutes before taking a reading and removing it? What is happening during this time?

b) How was the experiment designed to ensure the pressure of gas in the test tube was the same as the atmospheric pressure? Explain.

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Jamar FerryLv2

13 Dec 2019

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I did the experiment on a volatile liquid and got the data table. I managed to calculate the molar mass of the unknown compound. But it seems like something wrong that i couldnt identify the unknown liquid. I need help to calculate the molar mass and identify the unknown substance

1. Obtain and wear goggles. Conduct this experiment in a fume hood or well-ventilated area. 2. Trim a piece of aluminum foil so that it just covers the top of a small, 13 Ã 100 mm. test tube. est tube Use a needle to make a small hole in the middle of the foil. Measure the mass of the t and foil. 3. P a hot-water bath by warming about 300 mL of tap water in a 400 mL beaker. Keep the beaker on a hot plate once the water is warm. . Use a second 400 mL beaker to prepare an ice-water bath. Connect the Temperature Probe to LabQuest and choose New from the File menu. If you not auto-ID, manually set up the sensor. Obtain a liquid sample of an unknown volatile compound. Pour about 0.5 mL of the liquid into the test tube and quickly cover the test tube with the aluminum foil. Place the test the hot-water bath. Make sure that the foil is above the water level (see Figure 1). Immerse the Temperature Probe in the hot water bath (see Figure 1). Do not allow the tip of the probe to touch the beaker. This will give you a more accurate reading of the water bat temperature. You will monitor the temperature readings during the experiment. There is no need to store and graph data. Heat the beaker of water to boiling and maintain the boiling as your sample of liquid vaporizes. Note that some of your sample will escape the test tube through the needle ho the foil. This process also serves to flush the air out of the test tube. Keep the test tube in the boiling-water bath for at least three minutes after all of the liquid in the test tube has vaporized. Watch the temperature readings and record the temperature of the boiling-water bath, which will be used in the ideal gas law calculations. Use a test-tube holder to quickly transfer the test tube to the ice water bath. Cool the test tube for about one minute, then remove it and dry it completely. Measure the mass of the test tube and the aluminum foil top. Record the barometric pressure in the room. Rinse out the test tube and fill it to the top with tap water. Cover the test tube with aluminum foil. Measure and record the mass of the test tube, water, and foil. Advanced Chemistry with Vernier

I'm doing a chemistry lab, where I have to determine the molar mass of an unknown after finding the vapor density. So basically, I have to put 3 test-tubes in a hot water bath, after measuring their volume, and mass the test tube + condensed unknown. So, if, hypothetically, there was some unknown liquid left in the test tube when we were massing the test tube after we heated them, how would the experimental molar mass change? Would it increase or decrease? Or would it stay the same? I think it would stay the same, because, after all, it's the unknown liquid itself. But, then I'm worried about the fact that the gas doesn't fill up the volume of the entire test tube because that unknown liquid takes up part of the test tube...

Any help would be greatly appreciated! Thanks in advance!