General Biochemistry and biology I (FC, 09 -- 10)

Lab # 9: Molecular Weight of any Volatile Liquefied

one particular

Modified 8/19/2009


One of the essential applications of the best Gas Regulation is found in the experimental willpower of the molecular weight of gases and vapors. In order to measure the molecular weight of your gas or vapor, we really need simply to decide the mass of a presented sample with the gas under known conditions of temperatures and pressure. The gas obeys the perfect Gas Law.


Since the range of moles, d, is comparable to the mass, g, of the gas divided by their gram-molecular fat, M, following substituting we certainly have:



PV= (2)



M= (3)

This experiment consists of measuring the gram-molecular fat of a risky liquid utilizing the above formula. A small amount of the liquid can be introduced to a weighed flask. The flask is then placed in boiling water, the place that the liquid is going to vaporize totally, driving your air and filling the flask with vapor in atmospheric pressure and the temperatures of the boiling water. If we cool the flask so that the water vapor condenses, we can measure the pounds of the vapor and calculate a value pertaining to M. Do not forget that in all gas law challenges, temperature has to be in E. PROCEDURE

1 . Get yourself a round lower part flask, a stopper, tube and tiny cork, a cork band, an unknown water and a 1000 milliliters beaker. Support the flask on the natural ring all the time. With the arreter loosely put in the the neck and throat of the flask, weigh the empty dry out flask within the balance. Serve about five mL in the unknown the liquid into the flask. Assemble the apparatus because shown in figure 1 . Drape the complete assembly with aluminum foil but be aware that there is no possibility to get condensed normal water to spill into the flask. (Why? ) Poke a hole inside the foil close to the lip in the beaker in order that the steam can escape because far from the neck with the flask as is possible. Make sure there may be sufficient normal water in the a thousand mL beaker to cover almost all of the round bottom level flask. Standard Chemistry I (FC, 09 - 10)

Lab # 9: Molecular Pounds of a Volatile Liquid


Revised 8/19/2009

2 . Add a couple of boiling potato chips to the drinking water in the 1000 mL beaker and warmth the water to boiling. Be sure that the cork is not really inserted in the tubing in the neck with the flask. Observe the liquefied level within your flask; the amount should little by little drop while vapor escapes through the hat. After all the liquid has disappeared without more steam comes out from the cap, always boil this particular gently to get 1 to 2 mins. Measure the heat of the boiling water. Shut off the burner and wait until this particular has ended boiling (about ВЅ minute). Being very careful not to lose yourself, take away the aluminum foil and then release the grip holding the flask in position. Slide the actual flask, and immediately put in the small cork into the lines to seal the flask. 3. Involve the flask in a beaker of amazing water to a depth of approximately 4 centimeter. Alternatively, you could hold the flask under electricity. Do not allow normal water to enter the flask. Following holding the flask in the water for about 2 a few minutes to allow that to amazing, carefully remove the cork for not more than a second or two to allow air to, and once again insert the cork. (As the flask cools, the vapor inside condenses and the pressure drops, which explains why surroundings rushes in when the stopper is taken off. )

4. Dried the flask with a towel to remove the area water. Ease the cork momentarily to equalize any pressure variations, and reweigh the flask. 5. Look at the atmospheric pressure from the barometer.

6. Repeat the method using another 5 cubic centimeters of your not known sample. It is not necessarily necessary to wash or dry the flask at this point, simply put another 5 mL of the sample in to the flask. Eliminate the cork from the flask ahead of placing this in the beaker of hot water. Repeat measures 2, three or more, 4 and 5.

7. Bare any excess not known liquid in the flask in to the Organic Spend. Rinse the flask...


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