UK CHE 450 - CHE 450G SAFETY EXAMINATION

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1 CHE 450G SAFETY EXAMINATION Procedure: Before laboratory work in CHE 450G begins a student must pass the Safety Examination. A copy of the exam with answers is given to the new student by the group safety officer to study. When the student is ready to take the examination, the copy with the answers is returned and the student is supplied with a copy of the exam without answers. The test is administered by the TA in a location of his or her choice. The test is to be taken in private without outside resources. No time limit is imposed. The exam is to be graded by your TAs prior to beginning scheduled laboratory experiments. If incorrect or incomplete answers are given, the TA and/or instructor will review these areas with the student. The graded and reviewed exam is then passed on to the instructor. The TAs will then return a copy of the exam with answers to the student for future reference.2 Safety Exam Questions Part I. General Lab Safety 1. What safety references should you consult to assess the hazards of a chemical or planned experiment? The chemistry library has several texts on safety in the reference section: Prudent Practices in the Laboratory on-line summary http://www.hhm:.org/science/labsafe/lcss/start.htm Safety in Working with Chemicals Sigma-Aldrich Library of Chemical Safety Data Merck Index Aldrich Catalog On-line MSDS sheets: Univ. of Ill. MSDS telnet://romulus.ehs.uiuc.edu:3000 Fischer Scientific MSDS http://www.fischer.com:/cat.html Safety TechLine 1 800 356-2501 2. What steps should be taken when injured in lab? Get TA and instructor Stop bleeding if necessary Wash affected area with cold water (if chemicals are unreactive with water) Seek medical attention as necessary 3. Compressed gas cylinders are quite common in inorganic labs. Discuss their handling, use, and transport. Even if a gas cylinder contains an inert gas, it should be handled carefully because of the high pressures involved. Tanks should always be strapped or chained to a stable surface and should only be moved on a cart designed to transport them. A metal valve cover cap should enclose the valve before moving as well. Each type of gas requires a particular regulator. Oxygen tanks in particular require regulators free from hydrocarbon grease. Teflon tape should never be used. 4. General vocabulary as seen on the Safety Examination (answered verbally to the group safety officer): Dewar Aspirators Vacuum pump Schlenk line3 Alkali metal Rotary evaporator Mercaptan Heating mantles (Variacs) Base bath/Acid bath Phosphine Bleach 5. How should you dispose of the following reactive wastes? (each should be done in a well-functioning ventilation hood while stirring the mixtures) For more detailed descriptions see Prudent Practices for Disposal of Chemicals from Laboratories and/or http://www.chem.uky.edu/resources/stockroom/waste.html/ a. Oxidizing agents (chromates, permanganates, chlorates, etc.) Acidify a dilute solution (<5%) to a pH<3 with sulfuric acid and slowly add a 50% excess of aqueous sodium bisulfite. b. Sodium borohydride Add water slowly until the solution is less than 3%. Add excess aqueous acetic acid dropwise with stirring under nitrogen. c. Mercaptans and sulfides Add a 25% excess of bleach to oxidize these compounds with stirring; sometimes a more concentrated bleach substitute, calcium hypochlorite (swimming pool chlorine, HTH brand name) can be used. For a more detailed procedure see Prudent Practices for Disposal of Chemicals from Laboratories page 65. d. Alkali metals (a major source of laboratory fires) Add 3:1 kerosene:isopropanol or tert-butanol slowly while stirring. After gas evolution ceases, often several hours or days later, add 95% ethanol slowly with stirring. After the metal has been consumed, and no large solids are evident, add cold water slowly while stirring. Slowly add a 5% aqueous HCl solution until aqueous layer is neutralized (pH ~ 7). Place organic layer into the non-halogenated waste jerry can and pour the aqueous mixture down the sink so long as no solids are visible. e. Metal sulfides Add slowly to ice water. Keep in hood-H2S evolution. f. Nonmetal halides Hydrolyze these compounds by slowly adding them to a stirred 2.5 M solution of sodium hydroxide.4 g. Metal carbonyls Oxidize these compounds with bleach. h. Nonmetal alkyls (BR3, PR3, AsR3, etc.) To a dilute (<5%) solution (of the alkylating agent in an inert solvent), slowly add a 10% excess of tert -butyl alcohol in a high-boiling hydrocarbon solvent such as heptane under nitrogen. Add cold water and then 5% hydrochloric acid. i. Organomercury compounds Oxidize these compounds with bleach. Part III. Fires and explosions: Prevention and extinguishing. 1. There are four general classes of fires which are likely to pose a genuine threat to your laboratory safety. What are the four classes of fires and what type of extinguisher is required to put out each fire? Additional information is given below for your benefit, but you need only answer the highlighted question above. Class A fires: Ordinary combustible solids: paper, rubber, textiles. Frequently accompanied by destructive distillation producing flaming vapors or toxic gases. Also may leave hot ash or residue which may initiate ignition. Effectively extinguished by water, which is recommended if the water poses no further hazard. Also extinguished by CO2, N2, volatile halocarbons (CF3Br, etc.), and dry chemical extinguishers, though these may spread ashes due to rapid release of compressed gas from the extinguisher cylinder. Dry ice will usually rapidly smother these fires if it is readily at hand. Class B Fires: Involves flammable liquids. Spreading of the fire is a major complication which is commonly encountered if a vessel of flaming liquid is overturned or broken. Easily extinguished by the exclusion of air by covering it in an upright vessel or by blanketing in foam, CO2, N2, volatile halocarbons, or5sometimes dry chemical (depending on the situation). Again, dry ice or liquid nitrogen is very effective if it is at hand. Compressed gas extinguishers can lead to spreading and worsening of the fire if the force from the extinguisher overturns a vessel containing the flammable liquid. Class C Fires: These are Type A or B fires in which electrical equipment is involved. Can be


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UK CHE 450 - CHE 450G SAFETY EXAMINATION

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