Laboratory Manual Microscale Gas Chemistry

Transcription

1 Laboratory Manual MANY PEOPLE HAVE CONTRIBUTED TO THE DEVELOPMENT OF THE CHEM 1A LAB MANUAL OVER THE YEARS. SOME ARE CITED IN THE INDIVIDUAL SECTIONS. THE PRESENT MANUAL HAS UNDERGONE MAJOR REVISIONS TO INCORPRATE THE IDEAS OF GREEN CHEMISTRY. DR. MARTIN MULVIHILL AUTHORED MANY OF THE EXPERIMENTS ALONG WITH DR. DOUSKEY. PLEASE DR. DOUSKEY IF YOU FIND ERRORS IN THE MANUAL OR IF YOU HAVE SUGGESTIONS FOR IMPROVEMENT. The preparation of CO 2 experiment was provided for free and adapted with permission from Microscale Gas Chemistry, Educational Innovations, copyright Bruce Mattson, No royalties from the sale of this manual have been distributed to Dr. Mattson. 1

2 Table of Contents INTRODUCTION TO THE LABORATORY POLICIES DEVELOPING A MODEL AIRBAG HOW THE NOSE KNOWS ACID IN THE ENVIRONMENT I: PROPERTIES OF GASES ACID IN THE ENVIRONMENT II: INDICATOR TITRATION PRODUCTS, REACTANTS AND DYNAMIC EQUILIBRIUM ACIDS IN YOUR LIFE: POTENTIOMETRIC TITRATION BIOFUELS I: TOXICITY OF BIOFUELS BIOFUELS II: SYNTHESIS OF BIODIESEL BIOFUELS III: COMBUSTION OF BIODIESEL SOLUBILITY AND SPONTANEITY INQUIRY ON LIGHT RESEARCH PROJECTS APPENDIX: USING THE HP 8453 UV/VISIBLE SPECTROPHOTOMETER USING THE HANNA HI 9025 ph METER GRAPHING OF DATA EXAMPLE FORMAL LAB REPORT FOR AIRBAGS EXPERIMENT FALL 2011 LAB AND DISCUSSION CALENDAR 159 USEFUL CONTACT INFORMATION My GSI s contact information Name Phone Number Open Office Hours Closed Office hours address Lab Partners/ Friends in Lab Name Phone Number address Name Phone Number address Name Phone Number address 2

3 Green Chemistry and Chem 1A Chem 1A Labs are currently being redesigned to highlight green chemistry principles. The Twelve Principles of Green Chemistry* are shown below. You ll notice that the focus is primarily on the synthesis of chemicals, but many of the principles can be applied to Chem 1A experiments. 1. Prevention It is better to prevent waste than to treat or clean up waste after it has been created. 2. Atom Economy Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product. 3. Less Hazardous Chemical Syntheses Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment. 4. Designing Safer Chemicals Chemical products should be designed to effect their desired function while minimizing their toxicity. 5. Safer Solvents and Auxiliaries The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used. 6. Design for Energy Efficiency Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure. 7. Use of Renewable Feedstocks A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable. 8. Reduce Derivatives Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste. 9. Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. 10. Design for Degradation Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment. 11. Real-time analysis for Pollution Prevention Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances. 12. Inherently Safer Chemistry for Accident Prevention Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires. * Anastas, P. T.; Warner, J. C.; Green Chemistry: Theory and Practice, Oxford University Press: New York, 1998, p.30. Green Chemistry Learning Goals for General Chemistry: 1. Identify, evaluate, and minimize the use of hazardous chemicals. 2. Understand the origins and the fate of chemicals in the environment. 3. Design safer and more efficient chemical reactions and processes. 4. Gather data and effectively use both qualitative and quantitative metrics. 5. Communicate scientific data and concepts to both experts and the general public. 3

4 Green Chemistry Themes in Chem 1A Lab 1) Model Airbag This lab connects the efficient use of materials to the design of an effective product. Students maximize the incorporation of the starting materials into the final product, making this a practical example of Atom Economy. 2) How the Nose Knows This lab introduces students to the relationship between chemical structure and biological function. Like smell, toxicity can be hard to predict, but in both cases trends begin to emerge. This experience helps students begin to think about Designing Safer Chemicals. The naturally occurring fragrance molecules in this lab are examples of Renewable Feedstocks, and introduce students to the rich chemistry found in nature. 3) Acids in the Environment I: Properties of Gasses The students practice Real-time Analysis for Pollution Prevention during this lab as the monitor the partitioning of CO 2 into water. More importantly, this lab helps students understand how chemicals move through the environment. This lab helps students develop a foundation in basic environmental chemistry so that they will be able to design Less Hazardous Chemical Syntheses in the future. 4) Acids in the Environment II: Indicator Titration Students expand their understanding of both environmental and analytical chemistry during the second week of the acid rain labs. In order to assess potential environmental or health hazards, students must have a basic understanding of the tools used to quantify chemicals in complex mixtures. 5) Products, Reactants and Dynamic Equilibrium The final experiment of this lab guides students through the synthesis of a bio-based ink. Oak gal inks are made from Renewable Feedstocks using Safe Solvents and Auxiliaries (water and gum Arabic). The lab discusses degradation of the ink and the paper over time, introducing students to the idea that chemicals can be Designed for Degradation properties that match the chemicals intended use. 6) Acids in Your Life: Potentiometric Titration This lab helps students develop tools to identify and quantify chemicals. Amino acids are both academically rich examples and they also help students understand the importance of maintaining a stable ph to organism functions. All of the materials used during the experiment are Safe. 7) Biofuels 1: Toxicity of Biofuels Comparing various biofuel options allows students to appreciate the subtlety of Designing Safer Chemicals. Even though all of the fuels come from Renewable Feedstocks, they have significantly different effects on radish seed germination. 8) Biofuels 2: Synthesis of Biodiesel The discussion of reclaiming used cooking oil introduces a waste prevention strategy as well as using Renewable Feedstocks. The base-catalyzed transesterification reaction is both Solventless and Atom Economical. 9) Biofuels 3: Combustion of Biodiesel Biodiesel has a much lower flash point than other biofuels, making the combustion reaction Inherently Safer than burning the alcohol based biofuels. Measuring the heat of combustion allows students to evaluate the Energy Efficiency of biodiesel. 4

5 10) Solubility and Spontaneity This lab explores the thermochemical properties of borax, which is a Less Hazardous Chemical alternative that can be used in detergents, cosmetics, and enamel glazes. It is also used to make buffer solutions in biochemistry, as a fire retardant, as an anti-fungal compound for fiberglass, and as an insecticide. 11) Inquiry on Light This inquiry based lab allows students to extract natural dyes from carrots and other foodstuffs using ethanol. Ethanol is a much Safer Solvent compared to methylene chloride and the other halogenated solvents which have traditionally been used for extractions. The lab also gives students a chance to devise and optimize a set of procedures focusing on Energy Efficiency and Waste prevention. 5

6 Introduction to the Laboratory Welcome This year we are incorporating the concepts of green chemistry into the laboratory curriculum. We have tried to make the Chem 1A laboratory learning experience enjoyable by linking the lab and lecture portions of the class as closely as possible. The subject matter can be challenging to students. Be prepared to work hard. Seek help early if you feel you don t understand a concept. Use every resource you can - this manual, the textbook, the internet, your lab instructor, and your fellow students. The key to understanding chemistry is to grasp the big picture, or how all the little things you learn is part of the complete description of how matter and energy interact. You will have to focus on details, but as you re doing so, periodically think about how they fit into the big picture. Understanding concepts is more important than memorizing facts. If you truly understand the concepts, you will do well in the class. Course Requirements and Policies Successful Completion of the Laboratory Portion of the Course Attendance Please consult the detailed course policies posted on the course website. Your lowest lab report score for the informal lab reports will be dropped. Experiments 4 and 9 will require a formal lab write up and are mandatory. If you miss one of the experiments assigned to formal lab write ups (Exp. 4 and Exp. 9) due to illness, death in the family, or other unavoidable circumstances, you must discuss your absence with Dr. Robert Lamoreaux, lamoreau@berkeley.edu. He will help you to schedule a make up lab in the remaining sessions for the missed lab experiment. Please provide paper documentation of illness or family crisis. Everyone MUST check-out of lab and their locker, even if the course is dropped midway through the semester. Failure to do so will result in a minimum $25 fee plus breakage. Grading In order to receive points for any given lab, the following conditions must be met: You must attend lab. Prior to attending any given laboratory period you must have completed all of the reading assignments. You must prepare a prelab in your lab notebook. The prelab may be a series of discussion questions to be answered in groups or may be something you have to prepare in advance of attending lab. Your prelab must include, as a minimum, what is asked for in the laboratory manual at the beginning of the experiment. You must arrive to lab on time, which means no later than 8:10 AM for morning labs and 1:10 PM for afternoon labs. In general, the first minutes of every laboratory period are dedicated to a safety discussion, which is an important part of the experiment. Therefore, if you show up late you will not be allowed to participate in lab for that day. You must wear protective clothing and eyewear during the laboratory period. Your GSI can ask you to leave the lab for the day if you are not wearing such clothing or eyewear. You must record detailed observations about the experiment. Do not just make a checklist of what you are supposed to do and then check off the procedures as you carry 6

7 them out without making observations as to what actually happened. All observations must be written in your lab notebook during, not after, the laboratory period. You must record all expected data during, not after, the laboratory period. This includes the mass of chemical weighed, the volume used in titrations, etc. Before leaving lab, you must meet with your GSI who will ask you to confirm that certain data is present in your notebook. Upon confirmation, the GSI will initial the notebook. At this point, you are to provide them with the perforated pages of your notebook that were used in lab that day. You must complete the report (whether formal or informal) for the experiment. You must turn in the lab report at the beginning of the lab period it is due (the next lab period after the experiment was completed). Late lab reports will not be accepted. Lab reports cannot be submitted to the GSI using or any other type of electronic format. Any questions you have regarding a lab report grade must be resolved with your GSI within one week of having received the graded lab report. All regrades are subject to final approval by the course instructor. If you do not complete all of the above conditions for any given lab, you will receive a 0 for that experiment. The consequences of a 0 are as follows: If you receive one zero during the semester, this will be your dropped lab score. If you receive two zeros during the semester, you not only will lose the 10 points associated with that experiment, but your course grade will also be dropped by one third of a grade. For example, if you earn enough points to get a B+ in the class, but you have two zero s, you will receive a B. If you receive three zeros you will receive a failing grade in the course. 7

8 Collaboration, Cheating and Plagiarism You will work in groups on most lab experiments. We encourage you to work together on the preliminary work for lab reports as well. However, anything you hand in for a grade must be your own work. Work together and discuss the concepts and calculations but then write your final lab report alone. This will help you to ensure that your own thoughts are captured. If your instructor suspects you have copied a report of another student, or if sections of lab reports are exactly the same, the students involved will loose all the credit for that experiment. If you directly quote or paraphrase from an outside source, you must provide a citation of the source. If you do not you are in danger of committing plagiarism. The course instructor will further review any suspect lab reports and submit a form called FACULTY DISPOSITION FOR ACADEMIC DISHONESTY to the Office of Student Judicial Affairs. The findings may result in your dismissal from the course and possible further action by the Academic Senate. Laboratory Notebooks The required notebook for this course is the Hayden-McNeil Student Lab Notebook with numbered duplicate pages (a white page followed by a duplicate page, perforated for easy removal). It is available at the CAL Student Store and Ned s on Bancroft. Use a ball point pen in your notebook. You will be asked to hand in the duplicate sheets and retain the original notebook pages. You will be graded on the quality of your laboratory notebook. The purpose of your lab notebook is to record data and observations that allow you to understand and explain the purpose and results of the lab experiment. Some things that should be included for every experiment are: 1. The title and a brief statement of the purpose/goal of the experiment. 2. Data and results, usually organized in tables. You are often graded on your results. Record them carefully. 3. A record of observations, thoughts and questions. Guidelines for Keeping a Lab Notebook 1. On the first page of your notebook write: your name, your lab section, your GSI 2. On the second page start a table of contents. List the experiment title and the page numbers that contain your data as you go. 3. Always use a pen to write in your notebook. Mistakes should be crossed out, but left legible (they often turn out to be less of a mistake than you thought). 4. Write a flow chart showing the general procedure and calculation steps. This will help you to determine what data to collect and what you will be doing with the data. 5. Record all observations directly into your notebook, NOT in this manual or on scratch paper. 6. Keep your own notebook, even when working in groups. 7. Give the dimensions of numerical data and use the proper number of significant figures. 8

9 Laboratory Safety Safety is our number one chemistry laboratory concern. Please read and follow all safety instructions in this manual. Your laboratory instructor will explain safe working procedures throughout the semester. Don t hesitate to ask at any time if you do not understand a safety guideline or procedure. Completion of Safety Checklist In your second lab period, your lab instructor will provide you with and help you complete a safety checklist. You are required to initial each item and sign the checklist. General Safety Guidelines Emergency Response Your lab instructor will explain the purpose, and how and when to use the following: Eye Wash Safety Shower Accident Reports Emergency Phone Numbers Evacuation Route/Assembly Area For Earthquake or Fire Safe Operating Procedures Chemicals and equipment can be dangerous if mishandled. This course is designed to teach you the fundamentals of chemistry, and how to conduct yourself in a laboratory. Follow the guidelines below whenever you are in the laboratory. 1. SAFETY GLASSES are provided as part of the locker equipment. They must be worn at all times whenever anyone in the lab room is working on an experiment. 2. CONTACT LENSES are prohibited in the lab. 3. ALWAYS WORK NEATLY, plan ahead and clean up after yourself. Most laboratory accidents are a result of poor planning, clutter or spilled chemicals. Clean up spills immediately; ask your lab instructor for help. Your dried acid spill can seriously burn someone later. 4. GLOVES are provided in the stock room for handling corrosive chemicals. 5. FUME HOODS will be used to contain the more hazardous chemicals. Your lab instructor will explain their use. 6. GLASSWARE, pipettes, stirring rods, thermometers, etc., can cut, burn and puncture. Use care when handling glassware. Most injuries in our labs are cuts caused by broken glass. Your lab instructor will demonstrate good technique. 7. When mixing concentrated acid with water, always add the acid to the water. Adding water to concentrated acid can cause acid to splash out of the container. 8. Never pipette anything by mouth. 9

10 9. Use only as much of any reagent as you need collecting and treating leftover chemicals is both expensive and environmentally unfriendly. 10. When heating a solution in a test tube, do it by placing the tube in a beaker of boiling water, rather than by heating it directly over the Bunsen burner flame. 11. Follow carefully the indicated instructions for the collection of excess chemical solids and solutions. Never return unused reagents to their original bottles. When in doubt about proper collection procedures, consult your laboratory instructor. Environmental Impact In Chemistry 1A, we all do our part to reduce the environmental impact of the course. You can do your part to help save the environment by following the chemical collection guidelines offered here and weekly by your lab instructor. There will be several types of chemical collection containers available in every room. USE EACH FOR ITS DESIGNATED PURPOSE ONLY. Collecting and treating leftover chemicals can be expensive or impossible to dispose of safely. BSC (Bulk Spent Chemicals) Containers for chemicals that require special handling will be located in the fume hoods. These include containers for, Organic solvents and compounds Sulfides Toxic and/or heavy metals Strong oxidants Collecting and treating what is leftover of these chemicals requires great care. Mixing of these chemicals with other types of BSCs is dangerous and expensive. Always read the label on the BSC container before you pour anything into it. Corrosive Liquid Spent Chemicals For leftover corrosive liquids, use the plastic BSC containers located in your lab room. Be careful not to splash solutions. Glass containers should be rinsed once with a few ml of water which should be emptied into these containers. Further rinse water can be disposed of down the drain if you are sure that the rinse water does not contain significant amounts of acid, base or salt. Solid Chemicals Solid chemical by-products are collected in small white buckets labeled solid spent chemicals. If you are ever unsure about which container to use, or if a container is nearly full, notify your laboratory instructor immediately. Lab Debris (white bucket with yellow label) Lab debris is anything that is chemically contaminated that cannot be easily cleaned, such as paper towels used to clean up chemical spills, used droppers, used filter paper, contaminated or clean broken glass, broken porcelain, lab gloves and empty unknown vials. Do not put regular trash into these containers. General Trash (tall red container with yellow label) General trash containers will be located at the ends of the lab benches. Put common trash, paper, and uncontaminated towels or gloves, here. 10

11 50 ml NO ml ml NO ml NO NO NO NO NO C ml Locker Equipment BEAKERS FUNNELS ml 60 50mL 100 ml 80 ml ml 150 ml 130 ml ml 250 ml 200 ml ml 250 ml 400 ml 600 ml 300ml ml Short Stem Long Stem CENTRIFUGE TUBES FLASKS 250ml 250ml 50ml ml 50 ml Erlenmeyer 250 ml Erlenmeyer Florence Flask 125 ml Florence Flask 250 ml TEST TUBES OTHER GLASSWARE TEKK TEKK TO 20 C ml TEKK TO 20 C ml TEKK 20 C ml 100 PORCELAIN 18 X 150 (large) 25 ml Graduated Cylinder X 100 (small) 13 X 100 (medium) Test Tube Rack " Casserole Dish 17 ml Crucible with lid Evaporating Dish 100 ml Graduated Cylinder MISCELLANEOUS Wash Bottle 25 ml Burets Pipet Bulb 6 in. Glass Rods TD 5IN1/5ml 20 C TEKK Safety goggles Test Tube Holder Lab Marker Spatula Centrifuge Brush Test Tube Brush Tongs Matches Hayden-McNeil Publishing, Inc. Plastic Droppers Large Watch Glass, Pyrex Rubber Policeman 5 ml Volumetric Pipet 1 ml Graduated Pipet Thermometer, -20C - 100C

12 Activities During a Lab Period Prelab questions and Lab Reports Before you arrive in lab (except for the first week) you have to complete the prelab assignment available from the course website. Some weeks the answers to the prelab questions may be discussed in small groups. You will also hand in your lab report from the previous week at the beginning of the lab session, as soon as you enter the lab room. The lab reports will be either an informal report sheet or a formal typed out report. Discussion Your lab instructor will lead a discussion on topics relevant to the course and the experiment. These may include how the course and lab materials reinforce each other, some problem solving, and demonstrations of new lab equipment and techniques. Attendance of the discussion period is mandatory for students enrolled in Chem 1A lab and Chem 1A lecture. Experiment time You will usually have about 3 hours to complete your experiment and clean up your work space. Come to lab prepared. You ll get out of lab more quickly, understand more, and have more fun if you know what you re doing and what s expected of you. You must clean up your work space before leaving the lab, and before the end of the period. Plan ahead so you can be done on time. Before you leave Turn in the carbon copies from your lab notebook of your work in lab that day to your GSI. 12

13 Structure of Lab Experiments All the experiments you perform are described in this lab manual. They are organized as follows: Title Chem Connections The lecture and lab for Chemistry 1A are designed to complement each other. Chem Connections highlight the overlap between lecture, lab and real life. New Science The scientific background you need to complete the prelab questions and the lab experiment are described in this section. As noted above, references to other course material and the internet included as a resource for additional information. The Problem The lab may be comprised of one or more Investigations. This section will appear in all Investigations as a short, concise description of what you are expected to measure, determine, or investigate. The Approach This manual will provide you with step-by-step instructions in this section. Instructions that include a check box require that you record data or observations in your lab notebook (NOT THIS MANUAL). Check them off as you go to make sure you don t miss any data important for your report. In the Report The report sheets provided at the end of most experiments outline the results, calculations, error analysis and discussions you should include in your lab report. Each report sheet will follow the same format. Your report should always cover the material suggested and address the questions in this section within the standard report format. The lab report is what determines the bulk of your lab grade and it is described for you in the next section. 13

14 Your Laboratory Grade Please refer to the laboratory course policies for details on grading. Your grade for the laboratory portion of Chemistry 1A is based mainly on the quality of your lab reports. Most lab reports will be informal, just a tabulation of data and answers to a few questions using the report sheets provided at the end of each experiment in the manual. Two of the lab reports will be more formal. The idea of the formal lab report is to bring together the results of the experiment in a clear, concise way. The tone should be serious, clear, and to the point. There will be a limit to the length of the report, so avoid wordiness and tangential material. Reference the lab manual for any detailed or lengthy practical or theoretical discussions. The formal lab report must be typed, but hand-written calculations, equations, and diagrams are always permitted. Most formal lab reports are expected to be only one or two pages with some attached plots, tables and calculations. We recommend you use a word processor and not pages from your lab notebook. Transfer the data from your notebook to tables in the report. Keep in mind that you are telling a story. The plot line is what you tried to do (methods), a summary of the outcome (data and calculations), and a comparison between theoretical values (if available) and your results, including an analysis of errors (results and discussion). The biggest mistake you can make is to follow the order of the lab manual. This will make your report too long and awkward. Think about the lab experiment as a whole, re-read the Introduction section to get the big picture, and tell the story in a brief and concise manner. Use the guidelines on the next page to organize your formal report. 14

15 Formal Lab Write-Ups: For Experiment 4 (Indicator Titration) and Experiment 9 (biodiesel combustion) you will complete a full formal lab report. The lab report will follow the format of a scientific journal article and therefore should be typed with diagrams, tables, plots, and equations incorporated within the text. Even though students might share data, each student should write their own report. Plagiarism and cheating will not be tolerated. Formal lab reports are worth 16 points. In these reports, each section will be scored according to the criteria below. Abstract (2 points): The abstract is a one paragraph summary of the experiment which outlines the reason for carrying out the experiment and the important results. The overall goal is stated correctly, succinctly, and in the student s own words. The general approach to the experiment is described. The important results are summarized. Introduction (3 points): The introduction should provide background information on the experiment, the motivation for its being carried out, a hypothesis of the result, and a justification for the methods used. What experiment is being performed? Why is the experiment being performed? What will the data show? The section describes the theoretical basis by which the method is suitable for attaining the goals of the experiment. Methods (2 points): The method section is a brief description of the experimental procedure, but not a list of steps. The important aspects of the experimental method are presented. The relevant equipment and techniques are described. The laboratory manual is cited as a reference. Results (3 points): A discussion of the important results obtained in the experiment and the trends observed should be reported. Are the results in agreement with the hypothesis? All relevant data and results are presented and clearly labeled. Important features or trends are noted in the text. Calculations are connected to the method, theory and goals of the experiment. Sample calculations are shown. Calculations are complete and correct. Discussion and Conclusions (3 points): The section synthesizes, analyzes and interprets the results of the experiment. Results are thoroughly compared with purpose, expectations or theoretical calculations. Relevant discrepancies and errors are explained. Each error mentioned includes a discussion about the effect on the final values. The report demonstrates an understanding of the chemistry and purpose of the experiment. Future improvements are proposed. Organization, Quality of Writing, Grammar, etc. (3 points) The report tells a cohesive story with ideas supported by data. Data is logically organized (in tables if appropriate), labeled, and summarized in the text. All graphs and plots are logically organized, labeled, and summarized in the text. The lab notebook carbon copies are provided for reference. Report does not have spelling and grammatical errors. Appropriate verb tense is used for each section. Appropriate verb tense for formal lab reports is passive voice, third person, past tense. 15

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