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 results. 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. http://mattson.creighton.edu/Microscale_Gas_Chemistry.html