Solutions to Ask Yourself Questions

The lab notebook must (1) state what was done (2) state what was observed and (3) be understandable to a stranger. 

For 3 degrees of freedom in both standard deviations, F,abie = 9.28. calculated tablet SO Standard deviations are significantly different. 

For 4 degrees of freedom in the numerator and 3 degrees of freedom in the denominator, Ftabie = 9.12. calculated tabie SO Standard deviations are not significantly different. 

Actions Compare data and results with specifications. Document procedures and keep records suitable for meeting use objectives. Verify that the use objectives were met. 

Precision is demonstrated by the repeatability of analyses of replicate samples and replicate portions of the same sample. Accuracy is demonstrated by fortification recovery, calibration checks, blanks, and quality control samples (blind samples). 

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If you have been working your way through this epic in a more or less linear fashion, then you might have started to ask yourself some fundamental questions such as, How do you know if a vinyl polymer is isotactic, or atactic, or whatever How do you know the composition and sequence distribution of monomers in a copolymer How do you know the molecular weight distribution of a sample This last question will have to wait until we discuss solution properties, but now is a good point to discuss the determination of chain microstructure by spectroscopic methods. The techniques we will discuss, infrared and nuclear magnetic resonance spectroscopy, can do a lot more than probe microstructure, but that would be another book and here we will focus on the basics. 

Above all, don t be timid in the ambitiousness with which you ask questions. If you want to see the completed solution in a three-dimensional image, or to project yourself forward in time, or view some microscopic physical process, or view something not visible to your physical eyes, or re-experience some event out of the past, by all means ask. Don t let your questions be limited by your notion of what can and what cannot happen. 

In this chapter we have encountered many different situations involving aqueous solutions of acids and bases, and in the next chapter we will encounter still more. In solving for the equilibrium concentrations in these aqueous solutions, you may be tempted to create a pigeonhole for each possible situation and to memorize the procedures necessary to deal with each particular situation. This approach is just not practical and usually leads to frustration Too many pigeonholes are required, because there seems to be an infinite number of cases. But you can handle any case successfully by taking a systematic, patient, and thoughtful approach. When analyzing an acid-base equilibrium problem, do not ask yourself how a memorized solution can be used to solve the problem. Instead, ask yourself this question What are the major species in the solution, and how does each behave chemically ... 

You might be asking yourself why it is convenient to define a new function H. To answer that question, recall from Equation 5.5 that AE involves not only the heat q added to or removed from the system but also the work w done by or on the system. Most commonly, the only kind of work produced by chemical or physical changes open to the atmosphere is the mechanical work associated with a change in volume. For example, when the reaction of zinc metal with hydrochloric acid solution. 

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