Microscale Gas Chemistry Supplement Experiments with Gases

Document Sample
Microscale Gas Chemistry Supplement Experiments with Gases Powered By Docstoc
					                          Microscale Gas Chemistry
                   Supplement: Experiments with Gases

                                         Bruce Mattson
                                  Department of Chemistry
                                      Creighton University
                                Omaha, Nebraska, 68104 USA

       Both our book and parallel website are organized with the teacher and student in
mind. Part 1 is suited for use by a wide variety of audiences — ranging from middle school
physical science students up through university-level chemistry students.      Like most
experiments and demonstrations, results and observations can be discussed and interpreted
on a level appropriate for the students’ background. Part 1 includes the preparation of
carbon dioxide, hydrogen and oxygen along with over twenty experiments and
demonstrations with these gases. Both book and website includes background information
for each gas. The book includes questions for the students after each experiment. In most
cases, there are two levels of questions depending on the students’ level. (Answers are
provided in the appendix.) The website includes hundreds of color photographs, a growing
number of QuickTime movies and numerous links. The web version also includes electronic
versions of a growing number of experiments that can be downloaded for use (with
permission.) The summary of Part 1 is:

Part 1. Getting Started — 3 Simple Gases
 Getting Started — Generating Carbon Dioxide in a Large Syringe.

 A. Experiments with Carbon Dioxide
       1. Traditional limewater test for carbon dioxide
       2. Acidity of carbon dioxide
       3. Carbon dioxide extinguishes fires
       4. Carbon dioxide and aqueous sodium hydroxide react
       5. Carbon dioxide/carbonic acid equilibrium

 B. Preparation of Hydrogen and Experiments
     Preparation of hydrogen
     Experiments with Hydrogen
       1. Traditional test for hydrogen
       2. Hydrogen forms explosive mixtures with air
       3. Reversible conversion of copper metal and copper(II) oxide
       4. Reduction of iron(III) oxide with hydrogen
     Demonstrations and Advanced Experiments with Hydrogen
       5. Effusion of hydrogen is faster than air
       6. Hydrogen burns with a gentle flame
       7. Disappearing/reappearing candle flame
       8. Calcium and calcium hydride produce hydrogen in reactions with water
       9. Deuterium isotope effect

 C. Preparation of Oxygen and Experiments
     Preparation of oxygen
     Experiments with Oxygen
       1. Traditional test for oxygen
       2. Oxygen supports combustion
       3. Dynamite soap
       4. Hydrogen-oxygen rockets
     Demonstrations and Advanced Experiments with Oxygen
       5. Steel wool burns in oxygen
       6. The Blue Bottle experiment
       7. Oxygen makes the flame hotter
       8. Mini-sponge shooter
       9. Chemiluminescence

 D. Gas Bags
       Gases can be generated in much larger quantities using simple, gas bags made from
food storage bags and this is useful when students need a supply of several gases. For
example, in in some experiments students need both hydrogen and oxygen for several of the
experiments. The teacher may use the gas bag technique in order to prepare one or both of
these gases for the students in the interest of saving time.      One fascinating classroom
demonstration is done with a gas bag of hydrogen: Combustion of hydrogen in oxygen
demonstration. A flask as a musical instrument?
Part 2. Laboratory Experiments
       Part 2 consists of six full lab period experiments that can be used with carbon
dioxide, hydrogen and oxygen.        These experiments are suited for use by high school
chemistry students as well as university-level chemistry students.

       The experiments are given in approximate order of difficulty. “Mystery Gas” is a
good example of an inquiry-based learning lab. Students design and use a strategy to
determine the identities of three gas samples. “Percent Composition” relates the volume of
carbon dioxide produced from the acid decomposition of calcium carbonate to the composition
of an antacid tablet. The “Carbonated Beverages” lab is a set of experiments that explores
some of the properties of carbonated beverages and relates these observations to those made
my Joseph Priestley in the 1770s. The “Molar Mass” lab works well for any gas, not just the
three we have studied so far. It works especially well for heavy gases such as carbon dioxide,
propane. Results are generally within a few percent of the actual value — much improved
from the popular “molar mass of butane lab” that appears in many books.

       The last two experiments, “Limiting Reagent” and “Barometric Pressure”, along with
“Percent Composition” all require the entire class to share their data that everyone will then
use to complete the experiment.

Part 3. More gases
       The gases described in Part 3 and the experiments that go with them should be
conducted by individuals familiar and experienced with gas production using the syringe
method. Five of the six gases described in this part have properties that make their proper
use and handling more important than was the case for carbon dioxide, hydrogen and
oxygen. As with part 1, each experiment comes with questions for the students.

A. Preparation of Nitrogen Oxides and Experiments
   List of Experiments:
       1. Conversion of nitric oxide to nitrogen dioxide
       2. From nitrogen dioxide to nitric acid
       3. LeChatelier principle and the NO2/N2O4 equilibrium

       4. High temperature favors the endothermic substance
       5. Acid rain microchemistry
       6. Acidic nature of nitrogen oxides
       7. Well-plate reactions involving nitric oxide
      8. Dinitrogen trioxide is a blue liquid

B. Preparation of Ammonia and Experiments
   List of Experiments:
      1. Ammonia is a base
      2. Ammonia fountain
      3. Acid-base reactions with fruit juices
      4. Ammonia is more soluble at low temperature
      5. Gaseous ammonia reacts with gaseous hydrogen chloride
      6. Ammonia forms nitric oxide in the Ostwald process
      7. Ammonia forms complex ions with transition metals

C. Preparation of Ethyne and Experiments
   List of Experiments:
      1. Ethyne reacts with permanganate
      2. Sooty combustible of ethyne
      3. Banging bubbles!
      4. Ethyne/oxygen rockets
      5. Ethyne reacts with aqueous bromine

D. Preparation of Sulfur Dioxide and Experiments
   List of Experiments:
      1. Sulfur dioxide reacts with water
      2. Sulfur dioxide reacts quickly with sodium hydroxide
      3. Sulfur dioxide and potassium permanganate react
      4. Sulfur dioxide discolors many natural colors
      5. Acid-rain microchemistry
      6. Sulfur dioxide reacts with aqueous bromine

E. Preparation of Chlorine and Experiments
   List of Experiments:
      1. Chlorine and sodium hydroxide form bleach
      2. Chlorine disproportionates in water to form acidic species
      3. Chlorine discolors the natural colors of fruit juices
      4. Testing colorfast fabrics
      5. Chlorine reacts with aqueous sodium sulfite
       6. Halogen activity series
       7. Chlorine and sodium form sodium chloride
       8. Hydrogen/chlorine rockets
       9. Chemiluminescence and singlet oxygen.
       10. Spectacular underwater fireworks!
       11. Liquid and solid chlorine

F. Preparation of Nitrogen and Experiments

Part 4. Catalyst Tube Reactions
       In Part 4 we describe a series of experiments that can be performed with an
inexpensive, commercially available glass-encased heterogeneous palladium catalyst tube.
The catalyst tube is suitable for demonstrating gas phase reactions in the classroom or
teaching laboratory. In all cases, the products can be tested by simple chemical methods.
The reactions include:

       1. Oxidation of methane with air
       2. Oxidation of ethene with air
       3. Oxidation of carbon monoxide with air
       4. Hydrogenation of ethene
       5. Catalytic oxidation of ammonia
       6. Methane and nitrogen dioxide
       7. Carbon monoxide and nitrogen dioxide
       8. Decomposition of nitrous oxide
       9. Nitrous oxide and ammonia
       10. Nitrous oxide and carbon monoxide
       11. Nitrous oxide and methane

Part 5. Other Methods
       In Part 5 we present five gases that cannot be generated by the In-Syringe Method
because the reagents must be heated. Instead, we utilize a method that was first proposed
by LeBlanc over two centuries ago and involves heating two reagents together and collecting
the gas produced. We have modified the method to utilize 60 mL syringes for gas collection.
The Thermal Method is used to generate hydrogen chloride, carbon monoxide, ethene,
methane and nitrous oxide. For each gas, 6 – 11 experiments are described. Interested
readers are referred to our website for more information.
           In Part 5 we also introduce a third method for gas generation — using a microwave
oven. We have found this method works for generating ammonia, oxygen, carbon monoxide,
sulfur dioxide, methane and hydrogen chloride, however, the conditions vary wildly with the
microwave oven. For most purposes, the In-Syringe or LeBlanc methods give more reliable

Part 6. Advanced Gases
           The two gases described here are produced by the In-Syringe method. The
preparation of these gases and the experiments that go with them should be conducted by
individuals familiar and experienced with gas production using the In-Syringe method.
These two gases are considered “advanced gases” for different reasons. Silane is an
extremely pyrophoric gas and great caution must be exercised to prevent unintentional fires.
For hydrogen sulfide, it is its offensive odor and high toxicity that warrant the “advanced”
classification. Use of a fume hood is advised with both gases.

A. Preparation of Silane and Experiments
    List of Experiments:
           1. Silanes react with air
           2. Silane reacts with oxygen
           3. Silane reacts with chlorine
           4. Thermal decomposition of silane
           5. Reaction with aqueous potassium hydroxide

B. Preparation of Hydrogen Sulfide and Experiments
    List of Experiments
           1. Hydrogen sulfide is slowly oxidized
           2. Hydrogen sulfide is a weak acid
           3. Reaction between hydrogen sulfide and aqueous sodium hydroxide
           4. Hydrogen sulfide burns in oxygen with a howling blue flame
           5. Reaction between hydrogen sulfide and sulfur dioxide yields elemental sulfur
           6. Metal sulfide precipitation reactions
           7. Oxidation of metal sulfides

Our Microscale Gas Chemistry Website.
        Our gas book, numerous color photographs of procedures, experiments and
demonstrations, a few QuickTime movies of techniques and experiments are available on the
web at our microscale gas chemistry website. Equipment ordering information and historical
information are also available at the site. Use of the site is free.


Shared By: