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PURPOSE : In this particular laboratory experiment, we are going to determine the molar mass of an unknown gas, from the gas density. We are also going to use gas density, along with the kinetic molecular theory, to explain the behavior of gas filled balloons. Finally, we are going to demonstrate the effects of temperature and pressure changes of gasses.
PROCEDURE : We are using the experimental procedure as described in our laboratory manual.

University of Wisconsin - River Falls
Laboratory Manual
Chemistry 116

Experiment 116-8
Molar Mass From Gas Densities
Pages 81 & 82

There are no changes to this laboratory or from the indicated laboratory procedure.
MATERIALS and APPARATUS :
Part A-1: In this part of the experiment, we are going to observe three balloons filled each with one of three different gasses. So as part of our materials we need to have three balloons as well as the three gasses. These balloons were already prepared for us and we kept underneath the fume hood for observation.

Helium Sulfur Exofluoride
He SF6
4.002602 g. 146.06 g.
Laboratory Stock Laboratory Stock


Ammonia
NH3
17.031 g.
Laboratory Stock

Part A-2-5c: During this part of the experiment, our materials and equipment consisted of one, clean, dry, 500mL plastic bottle with an airtight cover. Along with the bottle we need an electronic balance, a thermometer set up to measure the air temperature, as well as a barometer with a chart on how to interpret the readings. Finally we must have the six different gasses with which to do our experiment.



Distilled Water Helium
H2O He
33.00674 g. 4.002602 g.
Laboratory Stock Laboratory Stock


Oxygen Argon
O2 Ar
31.9988 g. 39.948 g.
Laboratory Stock Laboratory Stock


Carbon Dioxide Propane
CO2 CH3CH2CH3
44.0098 g. 44.09652 g.
Laboratory Stock Laboratory Stock


Natural Gas
CH4
16.04276 g.
Laboratory Stock
Part A-6: In this particular part of the experiment we made two different balloons. Therefore we need the balloons themselves, as well as the two different gasses that are going to go into the balloons. One of the balloons needed to be filled with Helium and then the other one with Carbon Dioxide. Then the balloons were to be taken back to our place of residence for observation.

Helium Carbon Dioxide
He CO2
4.002602 g. 44.0098 g.
Laboratory Stock Laboratory Stock
Part B-1: For this part of the experiment we needed a balloon filled with air. We also tried this part of the experiment when the balloon was filled with two other gasses. A total of three more balloons will be needed for this lab then. We also needed some liquid nitrogen for this experiment. In addition to the liquid nitrogen, we need a pair of tongs to remove the gas filled balloon from the nitrogen.

Helium Carbon Dioxide
He CO2
4.002602 g. 44.0098 g.
Laboratory Stock Laboratory Stock






Nitrogen
N2
28.01348 g.
Laboratory Stock*

** Please note that Liquid Nitrogen is at an extreme temperature of
77 K. This will burn skin as well as freeze most objects it comes
into contact with. Take extreme caution.
Part B-2: For this part of the experiment, we needed a large water bath full of cold water. Additionally we need to have brought an empty soda can with us to class. ( I prefer Coca-Cola myself ) Then, on a ring stand over the wire gauze, we heated up ten milliliters of water in the can over a Bunsen burner. The goal was to turn all of the water to steam and keep as much as possible within the can. After the water had all turned to steam, we used the lab tongs and inverted the can in to the cold water, very quickly.
Distilled Water
H2O
33.00674 g.
Laboratory Stock
Part B-3: This final part of the experiment was demonstrated by our instructor. Our instructor used a bell jar and three different balloons filled with air, helium and one with water, to show the effects that the atmosphere around us has on different gasses and on water.
OBSERVATION and DATA :
Part A-1: In the table below, there are recorded observations from the three different balloons that were placed under the hood for us to observe. There were three different balloons, each filled a different gas.

He balloon feels light, the balloon rises in our atmosphere, there is a medium pressure
consistency feeling to the outside of the balloon

SF6 the balloon feels very full and tight, compared to the others this balloon feels very
heavy, this balloon feels like it would not float as easily as the rest of the balloons.

NH3 of all the three, this appears to be the lightest and most thin pressure consistency,
feels most light but does not respond to the atmosphere as well as the others
TABLE-1



Part A2-5a: During this part of the experiment, all we did was measure the densities