7# GZFADX}X}X}X}X}XfXXXYYY1Y1zYxXZ# ZCZr*ZX}ZrZ[ZrZrZZrZrZrZrZrZrINTRODUCTION TO THE GENERAL CHEMISTRY LAB The lab portion of the course is designed as an autonomous unit. There will be feedback in both directions, of course, between class and lab. Considerable effort has gone into timing the content of both components so that major topics such as thermodynamics and kinetics will not be encountered experimentally prior to their consideration in class. Nonetheless, the educational philosophy of the lab is that experimental chemistry has a life of its own. The goal of the lab, therefore, is to provide you with an introduction to the experimental aspects of chemistry. Centuries of empiricism have been invested in our present conceptual view of the physical world. It would be foolhardy to illustrate systematically the experimental basis of that view. Some principles will be illustrated in the lab, but many more will simply be applied to the problem at hand. Experimental work is an eminently practical activity. Our program is designed to provide you with an encounter with its methods, rewards, and undoubtedly with some of its frustrations as well. LABORATORY SAFETY The laboratory is a place for planned, serious work. To avoid accidents resulting from careless mistakes, maintain a business-like attitude in the laboratory. To avoid accidents resulting from unexpected problems, do not attempt unauthorized experiments. By taking your work seriously, working closely with your instructor, and adhering to the precautions and rules listed below, you will assure a safe semester in the laboratory. Our goal is to make the laboratory safer than your kitchen or home workshop. ACCIDENTS You should report any accident to your instructor at once, even a minor injury. EYE PROTECTION Goggles must be worn at all times by every student while he or she is in the laboratory. No exceptions will be made. Goggles may be worn over regular prescription glasses. The wearing of contact lenses in the lab is forbidden, even when wearing safety goggles. Contact lenses do not provide adequate eye protection, and in some cases may complicate an emergency situation. For example, caustic liquids splashed into the eyes may form a liquid layer beneath the contact lens; the eye-wash will not rinse out the caustic liquid adequately unless the lens is removed. Also, some organic liquids can actually dissolve the contact lens. If you do not have goggles on - you will be required to leave the laboratory. FIRES Know where the nearest fire extinguisher, fire blanket, and shower are located, and be acquainted with their use. After using an extinguisher, give it to your instructor for refilling; do not return it to its rack after use. Smoking is not allowed in the laboratory. Immediately notify your instructor of any burn. One procedure used when an individuals clothing is burning is called STOP-DROP-ROLL. STOP what you are doing, DROP to the floor, ROLL over and over to extinguish the flames. Do not run to the fire blanket or safety shower if your clothes are on fire, STOP-DROP-ROLL first. Someone else will get a fire blanket to help smother your burning clothes. BUNSEN BURNERS When used properly, the inner blue cone in the flame of a Bunsen burner should be approximately 3/4 tall (generally 1/2 to 1-1/2 tall). Adjustment of the Bunsen burner to provide for a taller flame is dangerous and should not be attempted unless supervised by an instructor. TOXIC CHEMICALS Chemists frequently work with toxic chemicals, some more toxic than others. In determining the danger a certain chemical poses, a chemist must consider how much of a chemical will enter his or her system under normal circumstances, and how poisonous that chemical is. Several of the substances used in this laboratory are poisonous, but when used properly and with caution, direct contact with such chemicals can be avoided. If you follow the directions in this lab manual, the chemicals pose no threat to your health. In the case of an accident, immediate corrective measures will remove any danger. The following guidelines are important when working in the lab: 1. Do not eat, drink, smoke or chew gum in the laboratory. 2. Wear safety goggles at all times. Keep your face well away from open flames, and watch the heating of solutions and crucibles from the side (never from above). 3. Pipet solutions only with a bulb, never with your mouth. 4. Avoid breathing dusts and vapors. Keep powders in covered beakers and work with volatile liquids under the fume hood. 5. Wash any splashed solutions immediately from your skin with plenty of water and notify your instructor. Also consult your instructor if a large quantity of any chemical is spilled on the lab bench. 6. Label all solutions and know which solutions present the most hazard. 7. Use all chemicals with caution. 8. Wash your hands before leaving the laboratory. The Hazard Communication Standard gives workers the right to know the hazards to which they are exposed. In compliance with the Standard, Material Safety Data Sheets (MSDS) are kept in lab for chemicals you will be handling. The MSDS sheet includes the name of the chemical (or components of a mixture), common names, physical and chemical characteristics, fire and explosion hazard data, reactivity data, health hazards and precautions for safe handling. A more comprehensive collection of MSDS for all chemicals located in this building is kept in Keyes 308A. Stock bottles of chemicals also contain safety information. This includes chemical name, manufacturer, health, flammability and reactivity hazards. The label also includes specific hazards unique to that chemical ( oxidizer, water reactive, etc.). The diamond on some bottles indicates these hazards also:  The numerals in the boxes in the diamond indicate the severity of the hazard with 0 indicating little or no hazard and 4 indicating severe hazard. For example, acetone (nail polish remover) has the ratings:  That is, the health rating (1) means acetone causes irritation, but only minor residual injury; the fire rating (3) means acetone can be ignited under almost all ambient temperature conditions (i.e., very flammable); and the reactivity rating (0) indicates that acetone is normally stable at high temperatures and with exposure to water (i.e., it is not explosive). WORKING WITH ACIDS AND BASES When diluting acid, pour the acid slowly and carefully into the water with constant stirring. Never add the water to the acid, since mixing this way may liberate so much heat that steam may form, causing the splashing of hot acid. Acid or base spilled on the skin should be washed off immediately with copious amounts of cold water. This is usually the only treatment necessary if prompt action is taken. If, through neglect of precautions (GOGGLES!), a chemical spatters into the eyes, immediate washing with large quantities of water is imperative. Use the eye-wash fountain nearby or place the head facing upwards in any sink and run tap water into the open eyes. Keep rinsing the eyes for a full 10-15 minutes. Consult your instructor immediately in case of an accident such as this. If your neighbor is the victim and needs help, you get the instructor. For acid spills on a person over a large area, immediately notify the instructor, who then might quickly remove all contaminated clothing while the person is under the safety shower. Neutralize spilled acid or base as follows: Acid on clothing --- use cold water and then dilute ammonium hydroxide. Base on clothing --- use cold water and then dilute acetic acid, followed by dilute ammonium hydroxide to neutralize any excess acid. Note: Occasionally a minor spill on your clothing will not be readily detected, especially on heavy fabric such as jeans. Sometimes holes will appear in the fabric only after it has been washed. We strongly discourage you from wearing expensive dress clothes to the lab. Acid or base on the desk top or floor --- neutralize with solid sodium bicarbonate (NaHCO3) or sodium sesquicarbonate (Na2CO3NaHCO32 H2O) and then wash off with plenty of water. CORROSIVE LIQUIDS AND VAPORS In any experiment in which poisonous or otherwise objectionable gases or vapors are discharged, perform the operations under the fume hood. This provides ventilation to remove such gases or vapors. You will be given specific instructions whenever an experiment requires using a fume hood. When observing the odor of any liquid, do not put your face directly over the container. Rather, fan a little of the vapor toward you by sweeping your hand over the top of the container. This will protect your nose and lungs from strong smells and harmful vapors. Heating any flammable liquid in an open flask with a flame is forbidden. Keep all flames away from volatile flammable solvents. Also, avoid using a flame when you or your neighbor are working with a flammable liquid. A hot liquid can suddenly form a bubble of vapor and bump, ejecting the contents upward. Add one or two boiling chips to solutions before heating to reduce the likelihood of bumping. Be sure to heat your solutions gently. Keeping the heated container well away from your face will prevent the liquid from splashing onto your face. Never point a test tube of boiling liquid at your neighbor or yourself. A suddenly formed bubble of vapor may eject the contents violently. GLASSWARE Accidents seldom occur, but when they do, they usually arise from the careless handling of glassware. Always observe the following rules: 1. Beware of hot glass. Glass cools very slowly, and may be very hot without appearing so. 2. Before inserting glass tubing into stoppers or rubber tubing, be sure that the hole is large enough to accommodate the glass. Use water or glycerine as a lubricant. Wrap a towel around the glass to protect your hands. Hold the stopper between your thumb and forefinger; do not hold the stopper in the palm of your hand. Grasp the glass tube close to the end that is to fit into the stopper and rotate the tube while pushing gently with an even pressure. 3. Do not attempt to push or pull glass tubing from rubber tubing, corks or stoppers that have become hardened. Cut the rubber or cork away from the glass. 4. Do not try to force an oversized stopper into the mouth of a flask or bottle. Always use a properly fitting cork or stopper. 5. Fire polish the ends of all glass tubing in a Bunsen burner flame to remove any sharp edges. REAGENT BOTTLES Keep the reagent bottles in their appropriate places on the side shelves and in the hoods. Transfer what you need to a suitable container and carry that to your desk. To avoid errors, read the label twice before taking anything from a bottle. Once taken out, do not return reagents to the bottles. DISPOSAL OF WASTE Dispose of all chemical wastes and excess reagents in the labeled containers at the front of the room. If there is no waste container for the substance, ASK the instructor before washing the substance down the sink. Never throw matches, litmus paper, glass, or any insoluble solid chemicals into the sink. Waste containers will be provided in the fume hoods for corrosive or toxic materials. UNATTENDED LABORATORY WORK Students may work in the laboratory only under authorized supervision. There are no exceptions to this rule. Never work alone in the laboratory. UNAUTHORIZED EXPERIMENTATION We strongly encourage students to devise new experiments. However, since untested procedures potentially involve risk, you must discuss your idea with your instructor before attempting an unscheduled experiment. LAB BENCH CLEAN-UP Each student must clear the top of his or her bench and remove all apparatus before leaving the laboratory. All materials taken from the front of the room at the beginning of the day must be washed and returned for use by other students on subsequent days. Wash and wipe off the bench top. Be sure that all gas jets, water faucets, and other services are off, and that any electrical equipment is unplugged. Check with your instructor before leaving the lab. GENERAL CONDUCT Horseplay, practical jokes, unnecessary noise, or the performance of unauthorized experiments in the laboratory may result in the endangering of lives. Such actions are strictly forbidden, and offenders will be expelled from the laboratory. The Chemistry Department is extremely concerned about the health and safety of all students in its laboratories. We must strictly enforce the rules for your protection. However, we also strive to ensure that your laboratory experience is both educational and enjoyable. THE NOTEBOOK Description and Use: One of the most useful skills to be acquired in the laboratory is the habit of using a laboratory notebook properly. A notebook, or formally kept record of some type, is an essential tool in many careers, ranging from research scientist to practicing physician. The effort invested in developing good habits of notebook use will be amply repaid for students who pursue a future in any profession which relies on careful observations. Experience indicates that skillful notebook use is best developed through continued special effort -- it does not come naturally. Some of the main principles of sound notebook use are outlined below. The laboratory notebook is a permanent, documented, and primary record of laboratory observations. Therefore, the notebook must be a bound journal with pages numbered in advance and never torn out. The first four pages should be left blank to accommodate a table of contents. Maintaining an up to date table of contents will save considerable time for you or your instructor when reviewing results. All entries must be in ink and clearly dated. No entry is ever erased or obliterated. Changes are made by drawing a line through an entry in such a way that it can still be read and placing the new entry nearby. When changing a primary datum, enter a brief explanation of the change (e.g. "balance drifted" or "reading error"). No explanation is necessary for a change in a calculation or discussion; the section to be deleted is simply negated by drawing a neat "x" through it. Commonly, observations are recorded on the right-hand pages and calculations on the left -hand pages of lab notebooks, but this is not mandatory. The ultimate goal is that anyone should be able to read your notebook, repeat the experiment with no confusion, and obtain the same results (within experimental error). This can be accomplished in a variety of ways. Since your notebook is a primary record, the source of any data copied into it (such as a lab partner's notebook in a joint experiment) must be clearly acknowledged. Observations are always recorded directly into your notebook and never collected on note pads or other temporary paper for later transfer into your notebook. It is important, therefore, to develop a standard approach to using your notebook routinely as the primary receptacle of observations. General Format for Experimental Records: A laboratory notebook should be neat and data should be readily accessible. For each experiment the following outline is appropriate: 1. Objective State the purpose of the experiment along with a brief statement of basic principles involved. Two or three sentences are adequate. 2. Procedure Report the procedure used in the experiment or reference the source for the experiment such as a handout or lab text. Any change in procedure should be clearly indicated in your notebook. If the experimental work is done jointly, the collaborator(s) must be identified. 3. Data and Results If an experiment involves a sequence of unique operations, the quantitative data and relevant qualitative observations are best entered in a running commentary. This commentary should be recorded as the experiment proceeds. High prose standards are not expected. If repeated measurements are made using the same procedure, a table provides the best presentation. Suppose, for instance, that several titrations of hydrochloric acid samples were carried out with 0.1042 M sodium hydroxide. The table below would provide a good format: Conc. NaOH = 0.1042 M Vol. HCl Vol. NaOH Conc. HCl 2.00 ml 3.02 ml 0.158 M 2.00 3.00 0.157 5.00 7.44 0.155 10.00 15.10 0.158 In a situation of this type a sample calculation must be shown to indicate how a typical result was obtained. F(VNaOH X CNaOH, VHCl) = CHCl For example, for the first entry: F((3.02 ml) X (0.1042M), 2.00 ml) = 0.158 M 4. Graphs It is often extremely useful to present a graphical interpretation of data. There are several computer programs available that greatly streamline data manipulation and produce statistical information for you. Among these are Excel, CricketGraph, and StatWorks. If you are not familiar wtith any of these programs, you are highly encouraged to begin using them. Help will be available to you during some of the laboratory periods. Regardless of the method you select, there are several factors to remember when graphing: a. the graph itself should be large enough to convey the information clearly, b. axes should be labeled, including units where appropriate, and c. if values are to be read from computer generated graphs, appropriately spaced grids should be included. Note that if you fit your data to a straight line, computer programs will automatically write the equation of the line for you. Calculating a value by using the fit equation is both easier and more accurate than "reading off" the graph. 5. Discussion A discussion of the experiment should include any conclusions drawn from the results, a brief explanation of the logic which produced the conclusion as well as comments on the precision and accuracy of results, and on any errors, along with possible explanations for them. CH 141 Lab: Introduction -- -- CH 141 Lab: Introduction  vx|rru$ @ +! 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