Conceptual study diagram

Based on experimental studies of the oxidation of methane mixtures with C2—C4 hydrocarbons and the demonstrated possibility of selectively reducing the content of C2—C4 hydrocarbons in such mixtures (Chapter 10), the authors of [303] proposed a two-step process of conversion of mixtures of methane with alkanes C24- to syngas. Proceeding from material balance of the process, a conceptual flow diagram of oxidative prereforming was proposed (Fig. 11.27). 

This section describes exemplary ways that diagrams of the sub-micro level can be used effectively in the chemistiy classroom. Three case studies are presented each identifying a particular conceptual or instractional difficulty and a suggested pedagogical approach that addresses the difficulty. 

There is a conceptual model of hydrated ions that includes the primary hydration shell as discussed above, secondary hydration sphere consists of water molecules that are hydrogen bonded to those in the primary shell and experience some electrostatic attraction from the central ion. This secondary shell merges with the bulk liquid water. A diagram of the model is shown in Figure 2.3. X-ray diffraction measurements and NMR spectroscopy have revealed only two different environments for water molecules in solution of ions. These are associated with the primary hydration shell and water molecules in the bulk solution. Both methods are subject to deficiencies, because of the generally very rapid exchange of water molecules between various positions around ions and in the bulk liquid. Evidence from studies of the electrical conductivities of ions shows that when ions move under the influence of an electrical gradient they tow with them as many as 40 water molecules, in dilute solutions. 

Cotecchia et al. (1974) studied the salinization of wells on the coast of the Ionian Sea. A fingerprint diagram (Fig. 6.23) served to define a conceptual model. The lowest line (MT) is of a fresh water spring and the uppermost line (I.S.) is of the Ionian Sea water. The lines in between (SR and CH) are of groundwaters with increasing proportions of seawater intrusion. The CH well met the nondiluted seawater at a depth of 170 m. This interpretation seems to be well founded as it is based on six dissolved ions. The whole story is condensed into one fingerprint diagram. 

FIGURE 6.1 Conceptual diagram of fit for purpose biomarkers method validation. The method validation processes include four activity circles prevalidation (preanalytical consid eration and method development), exploratory method validation, in study method validation and advanced method validation. The processes are continuous and iterative, dictated by the purpose of the biomarker application. The solid arrows depict the normal flow of biomarker development (prevalidation), method validation (exploratory or advanced), and application (in study method validation). The process could include moving the chosen biomarkers from exploratory mechanistic pilot studies to advanced validation and confirmatory studies, or from exploratory validation to advanced validation after changes in critical business decision. The broken arrows represent scenarios where validation data do not satisfy study requirements, necessitating assay refinement or modification. 

If we look at a piece of chemical text, we see that it is made up of characters, generally numeric digits, alphabetic characters, punctuation marks, and perhaps a few special symbols and diagrams. Information is conveyed by arranging these characters and symbols into particular sequences, words, numbers, etc., which convey particular meanings. Even a superficial study is sufficient to diow that there are basically three different types of information — numerical, structural, and conceptual. 

In this chapter we describe the kinds of phase behavior that are commonly observed in pure fluids, binary mixtures, and some ternary mixtures. The descriptions typically take the form of phase diagrams, and we show how studies of phase behavior can be made systematic by identifying classes of diagrams. Since we are interested in describing what is actually seen, the mixture diagrams presented in this chapter are plotted in terms of measurables usually temperature, pressure, composition, or a subset of those. Calculations of phase equilibria necessarily involves conceptuals, and such calculations are discussed in Chapter 10. Here we only describe phenomena. 

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