Open-ended laboratory

When conducting an assessment of an outside laboratory, the adequacy of the laboratory s QAU and its relationship to management should be determined in addition to assessing the laboratory operations. Questions directed toward evaluating the QAU might include those in Table II. It is often helpful for the QAU to make up a checklist however, the list should be flexible and open-ended so that it can incorporate unanticipated events. 

When students first start working in a more open-ended, student-centered laboratory environment, they typically have many more questions than in a traditional laboratory, and they are almost afraid to make a move without first consulting the instructor. They want to know the right way to proceed. As students continue to work in such a setting throughout the semester, many exhibit increased confidence and independence. 

Density is always introduced sometime in the early weeks of the first-year chemistry course. Traditional laboratory experiments have students determining the density of water or ethanol. Teachers usually set up a density column with various liquids and solids to demonstrate differences in density. Why not substitute Densities for this experiment It has directions on setting up a polymer density column, and the students can use part one of the experiment to understand the concept of density. This can be a second density experiment after the traditional experiment. The students can be presented with the solutions of various densities and several samples of known polymers and an unknown polymer. (Some scientific supply companies sell polymer samples to be used for specific gravity experiments. Used in density experiments, they eliminate the problems of floating or air bubbles.) Ask students how density would be used to sort the polymer samples. This can be a more open-ended experiment and may prove somewhat challenging but would be excellent, especially for honors students. 

In Appendix A, calculations show a status, for fuel cell isothermal Faradaic oxidation, of a high vacuum of reactants relative to a high concentration of product. That calculated status cannot even be approached in the laboratory, for lack of adequate semi-permeable membranes and circulators (concentration cells). The equilibrium fuel cell of Figure A.l is dead-ended, whereas the air-breathing open-ended design must have both of its electrodes swept by a parallel flow, with an inlet and an... 

Process Loosen the Hofmann screw, pour into A water that has been standing in the laboratory for at least twenty-four hours, until the reservoir, E, is two-thirds full then tighten the screw and add more water until the level tube, is three-fourths full clamp A at any convenient height to the iron stand which supports the apparatus. Pinch B to remove any imprisoned air. Fill the eudiometer, F, with some of the same water, invert in the reservoir, and clamp it so that the open end is just below the surface and near the wall of E. 

A shock-wave study of the H2-Br2 reaction has been performed by Plooster and Garvin over the temperature range 850-1140 °K for the purpose of extending thermal and photochemical work done at temperatures below 600 The reaction was followed by spectrophotometry of the Br2 concentration in the 4100-4200 A region. The shock tube was of the open-ended variety, the driver gas being the laboratory atmosphere. 

What is the pressure drop (mm Hg) from point (a) to point (b)7 3.44. An open-end mercury manometer is connected to a low-pressure pipeline that supplies a gas to a laboratory. Because paint was spilled on the arm connected to the line during a laboratory renovation, it is impossible to see the level of the manometer fluid in this arm. During a period when the gas supply is connected to the line but there is no gas flow, a Bourdon gauge connected to the line downstream from the manometer gives a reading of 7.5 psig. The level of mercury in the open arm is 900 mm above the lowest part of the manometer. 

I he previous chapters showed how the laws of conservation of mass and con--1- servation of atomic identity, together with the concept of the mole, determine quantitative mass relationships in chemical reactions. That discussion assumed prior knowledge of the chemical formulas of the reactants and products in each equation. The far more open-ended questions of which compounds are found in nature (or which can be made in the laboratory) and what types of reactions they undergo now arise. Why are some elements and compounds violently reactive and others inert Why are there compounds with chemical formulas H2O and NaCl, but never H3O or NaCli Why are helium and the other noble gases monatomic, but molecules of hydrogen and chlorine diatomic All of these questions can be answered by examining the formation of chemical bonds between atoms. 

Large quantities of substances which do not act on metals may be heated under pressure in closed vessels, generally made of iron, bronze or copper (autoclaves). Such vessels are not suited for heating acid substances, but may be used for neutral or alkaline substances. In this laboratory Mannes-mann tubes (without seams) are in- use, one end being welded together, and the other is supplied with a screw-thread and cap. The open end is cone-shaped. 

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