Check-In, Lab Safety, Balance and Volumetric Glassware Use, Introduction to Statistics, and MSDS Familiarization

Transcription

1 Check-In, Lab Safety, Balance and Volumetric Glassware Use, Introduction to Statistics, and MSDS Familiarization Before coming to lab: Read Chapter 2 of your textbook before coming to lab. This chapter is an excellent source of lab techniques and should serve as a reference for techniques to be used during the semester. Record the tolerance of a Class A 50 ml buret in your notebook see page 41 of your textbook. Record the tolerance of a Class A 10 ml pipet see page 44 of your textbook. Record the tolerance of a Class A 100 ml volumetric flask and 10 ml volumetric flask see 43 of your textbook. A note on Report Sheets: All data collected during lab must be recorded in your lab notebook. The report sheet should be filled out after all calculations are done in your lab notebook. (One exception today is Procedures 3 and 4, which may be completed directly on the report sheet.) Your Lab Noteook is a record of the work you do in lab. If your report sheet is lost by yourself or your instructor, you must be able to quickly and easily recreate it using your lab notebook. (This happens often.) All data must be recorded directly into the notebook during lab numbers, color changes, etc. Calculations can be done in the lab notebook either during lab or afterwards. SAFETY: Safety is of primary concern when in the chemistry lab. Remember that you are primarily responsible for your safety in the laboratory. If you have any questions about the safety of any action, check with the instructor. The wearing of safety glasses at all times in the laboratory will be vigorously enforced. Safety considerations: If any glassware is broken during lab, alert your instructor immediately. She/he will assist you in sweeping the broken glass into the dustpan and depositing it in the broken glass container. Wear gloves at all time (except on your pipetting hand while pipetting). Even though we re only working with water in this experiment, wearing gloves while doing experiments in this lab needs to become a habit. In this week s lab you ll be finding important safety features including the eyewash/safety shower, fire extinguisher, fire alarm, etc. This is very important information, make sure you see each item and remember where they are. MSDS - MATERIAL SAFETY DATA SHEETS: A Material Safety Data Sheet (MSDS) is designed to provide chemical, physical, and health and safety information on reagents and supplies. MSDS sheets also provide workers and emergency personnel with the proper procedures for handling or working with chemical substances. While there is no universal form for an MSDS, these forms will provide information such as physical data (melting point, boiling point, flash point, etc.), toxicity, health effects, first aid procedures, chemical reactivity, safe storage, safe disposal, protective equipment required, and spill clean-up procedures. Anywhere any type of chemical is used, an MSDS is required to be readily available, even for cleaning supplies at a daycare center or a grocery store. BALANCE USE: Analytical balances are accurate and precise instruments used to measure mass. They are expensive so handle them with great care. Since virtually every experiment starts with the Page 1 of 5 introductory exercise.pdf

2 weighing of an unknown sample or standard, it is critical that you learn to make accurate mass measurements. No amount of statistics or guesswork can make up for an inaccurate weighing. Top Loading Balances are used when less precision is acceptable. We use this balance for weighing many chemicals that are not unknowns or standards (i.e., not our limiting reagent). Chemical Toxicity The danger associated with a given chemical is dependent on its inherent toxicity and on the extent of exposure. Exposure is evaluated in terms of dose, duration, frequency, and route. It is always important to consider the toxicity of both starting materials and the products that form during reactions. Some chemicals may have low volatility and thus provide little risk for inhalation, but may be quickly absorbed through the skin. Mixtures may be more toxic than individual components; a solvent may be relatively harmless on its own, but could facilitate the absorption of another chemical into the body. To find information on a chemical s toxicity, use the following resources: 1) Labels: this is the easiest thing to check, as they are right on the chemical bottle. Labels will not provide in-depth quantitative information, but they will usually tell you the types and levels of hazard posed by a chemical. A typical chemical bottle label: Some common hazard definitions: Asphyxiant: a substance that can cause unconsciousness or death by suffocation Carcinogen: a substance that causes or is believed to cause cancer Corrosive: a highly reactive substance that causes obvious damage to living tissue Emetic: a substance that causes vomiting Fetotoxin: a substance that can poison or cause degenerative effects in a fetus or embryo Lachrymator: an irritant that causes tearing Mutagen: a substance that causes an increased rate of gene mutation (sometimes leading to cancer) Poison: a substance that adversely affects one s health by causing injury, illness, or death Sensitizer: a chemical that often causes exposed people to develop an allergic reaction Teratogen: an agent that can cause malformations of an embryo or fetus Make sure you know these definitions, you will be held responsible for knowing them. Page 2 of 5 introductory exercise.pdf

3 NFPA (National Fire Protection Association) information (often found in a diamond) is designed to give general hazard information for chemicals: The Health Hazard Section is blue; Fire Hazard is red, Reactivity is yellow, and Specific Hazard is white. For the first three sections, in each case they are rated from 0-4, with 4 indicating the highest hazard level. For more information about the chemical, its hazards, proper handling and emergency response, use the MSDS. The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapor may cease to burn when the source of ignition is removed. The flash point is not to be confused with the autoignition temperature, which does not require an ignition source, or the fire point, the temperature at which the vapor continues to burn after being ignited. Neither the flash point nor the fire point is dependent on the temperature of the ignition source, which is much higher. The flash point is often used as a descriptive characteristic of liquid fuel, and it is also used to help characterize the fire hazards of liquids A PowerPoint presentation about the NFPA diamond may viewed at the URL Page 3 of 5 introductory exercise.pdf

4 EXPERIMENTAL PROCEDURE Data and Calculations for procedures 1-2 should be recorded in your lab notebook. Procedures 3-4 may be filled in directly to the report sheet; this information does not need to be included in your lab notebook. Your instructor will initial and date your notebook entry before you leave today. PART ONE Procedure 1: MEASURING MASSES ON THE TOP LOADING BALANCES Record all data in your lab notebook before entering it onto the report sheet. 1. Record the mass (in g) of metal samples A, B, C and D in your notebook. Record the number of the balance used. 2. Obtain the results from 3 other students at neighboring lab stations. Record each student s name with their data. For each sample (A, B, C, D), calculate the following statistical results in correct significant figures: Mean Standard Deviation Coefficient of Variance, also called % Relative standard deviation, % RSD The 95% confidence interval (using t). All of the above calculations can be found in your textbook. 3. From the data, determine what metals you have and record the true atomic mass for each. Determine whether the true value falls within your 95% confidence interval. (Note: one or more of the samples may be corroded; would you expect to get a mass that accurately corresponds to the mass of the pure metal? Keep this in mind.) 4. Obtain the mean results for the four samples from another lab group calculate t for the comparison of means. Record the name of each student in that group. Calculate t for the comparison of means. Based on this result, are your group s results significantly different from the other group? Procedure 2: LEARNING TO READ THE NFPA DIAMOND Reproduce the NFPA diamond from one of the reagent bottles in the lab. Identify the chemical by name, give its chemical formula, and complete the other information requested on the lab report sheet. Procedure 3: LEARNING TO READ MSDS DATA SHEETS 1. Use an internet search engine such as Google to obtain MSDS data for 6M HCl. Fill in the table on your Report Sheet. 2. Take the MSDS quiz at the URL Print the certificate at the end of the quiz to turn in with your report sheet. Procedure 4: LAB DIAGRAM Familiarize yourself with the locations of the fire extinguisher, fire blanket, eyewash station, nearest fire alarm (in the hall), safety shower, and the exits in room 323. On the lab diagram included in the Results Sheet for this experiment, label the location of each of these. Page 4 of 5 introductory exercise.pdf

5 When you locate the eyewash/station station, don t pull the handle for the shower. Do pull the eyewash down to familiarize yourself with this. Before you leave lab today: Have your instructor date and initial your lab notebook. Do this every week. What to turn in: Submit the Part 1 Report sheets and MSDS quiz certificate. Report sheets are always due within one week. PART 2 Procedure 5: CALIBRATION OF VOLUMETRIC GLASSWARE Follow the instructions on pages of your textbook concerning calibration of volumetric glassware. Calibrate a 10-mL pipet, 50-mL buret and 10-mL volumetric flask. Use distilled water and record the temperature to one decimal place. Record all data in your lab notebook before entering it onto the report sheet. Use your 250-mL Erlenmeyer flask and a top loading balance for calibrating your 50-mL buret to the nearest milligram. Follow instructions on page 52 of your textbook, except use a 250 ml flask (instead of 125 ml flask) and don t use a stopper. You do not need to prepare a calibration graph described in #4. A difference of ±0.05 ml is acceptable if you can t get your difference within the ±0.02 ml recommended in the book. Use your weighing bottle and an analytical balance for calibrating the 10-mL pipet to the nearest tenth of a milligram. Do this at least five times. Be sure to start with a dry weighing bottle; dry it with a kimwipe each time you start a new measurement. Remember, fingerprints and drops of water will affect your accuracy. Use a top loading balance for calibrating your 100-mL volumetric flask to the nearest milligram. Record only your best result on the results sheet. Use an analytical balance for calibrating the 10-mL volumetric flask to the nearest tenth of a milligram. Be sure to start with a dry volumetric flask. Record only your best result on the results sheet. Don t forget to get your lab notebook dated and initialed by your instructor. What to turn in: Submit the Part 2 Report sheets. Latest revision: Page 5 of 5 introductory exercise.pdf