Chemical formulas significance

Exact numbers, such as the stoichiometric coefficients in a chemical formula or reaction, and unit conversion factors, have an infinite number of significant figures. A mole of CaCb, for example, contains exactly two moles of chloride and one mole of calcium. In the equality... 

In the realm of chemical enumeration we note Polya s equation (4.4) which gives the generating function for stereoisomers of the alkyl radicals, or equivalently, alcohols — that is, equation (5.2) of this article. His equation (4.3) gives the corresponding result for the structural isomers of these compounds. His equations (4.2) and (4.5) correspond, respectively, to the cases of alcohols without any asymmetric carbon atoms and the number of embeddings in the plane of structural formulae for alcohols in general. The latter problem is not chemically very significant. 

The student conceptions that were displayed could be categorised into three main types, namely (1) confusion between macroscopic and submicroscopic representations, (2) extrapolation of bulk macroscopic properties of matter to the submicroscopic level and (3) corrfusion over the multi-faceted significance of chemical symbols, chemical formulas as well as chemical and ionic equations. Student conceptions held by at least 10% of the students who were involved in the alternative instractional programme were identified. Several examples of student conceptions involving the use of the triplet relationship are discussed in the next section. 

In the usual chemical formulas written for chain polymers the sue-cessive units are projected as a co-linear sequence on the surface of the sheet of paper. This form of representation fails to convey what is perhaps the most significant structural characteristic of a long polymer chain, namely, its capacity to assume an enormous array of configurations. This configurational versatility is a consequence of the considerable degree of rotational freedom about single bonds of the chain. In the simple polymethylene chain, for example, the conventional formula... 

Widespread medicinal use of colloidal bismuth subcitrate (CBS) has prompted extensive studies of bismuth compounds involving the citrate anion. Bismuth citrate is essentially insoluble in water, but a dramatic increase in solubility with increasing pH has been exploited as a bio-ready source of soluble bismuth, a material referred to as CBS. Formulation of these solutions is complicated by the variability of the bismuth anion stoichiometry, the presence of potassium and/ or ammonium cations, the susceptibility of bismuth to oxygenation to Bi=0, and the incorporation of water in isolated solids. Consequently, a variety of formulas are classified in the literature as CBS. Solids isolated from various, often ill-defined combinations of bismuth citrate, citric acid, potassium hydroxide, or ammonium hydroxide have been assigned formulas on the basis of elemental analysis data or by determination of water and ammonia content, but are of low significance in the absence of complementary data other than thermal analysis (163), infrared spectroscopy (163), or NMR spectroscopy (164). In this context, the Merck index lists the chemical formula of CBS as KgfNHJaBieOafOHMCeHsCbh in the 11th edition (165), but in the most recent edition provides a less precise name, tripotassium dicitrato bismuthate (166). 

Commercially significant zeolites include the synthetic zeolites type A (LTA), X (FAU), Y (FAU), L (LTL), mordenite (MOR), ZSM-5 (MFI), beta ( BEA/BEC), MCM-22 (MTW), zeolites E (EDI) andW (MER) and the natural zeolites mordenite (MOR), chabazite (CHA), erionite (ERl) and clinoptiloUte (HEU). Details of the structures of some of these are given in this section. Tables in each section lists the type material (the common name for the material for which the three letter code was established), the chemical formula representative of the unit cell contents for the type material, the space group and lattice parameters, the pore structure and known mineral and synthetic forms. 

It can be surmised that even though X-ray data indicated only expandable material, there must be significant interlayering with illite or other non-expandable mica-like phases such as glauconite-celadonite in order to give such a high structural charge imbalance. If not, one wonders why illites, with a similar chemical formula, are not expandable as well. 

In addition to the more or less general references [9-13] cited above we wish to mention a significant and relatively early paper by Polansky and Rouvray [14]. It contains an explicit treatment of the benzenoid chemical formulas (C HS) and their invariants (n, s). This treatment seems by and large to have been overlooked in later works. 

Appendix C contains the chemical formulae for the minerals used in this book. There are very few minerals that have the ideal crystalline structures discussed above. There are sufficient substitutional impurities, crystal defects, and distortions that make the CBPC structure significantly different from the models discussed above. Several well-established minerals exhibit these features, as are many of those listed in Appendix C. For example, Ca(UO2)2(PO4)2T0H2O is formed by the substitution of Ca in autunite by uranyl (UO2) ions, making the autunite a mineral of radioactive uranium. Similarly, (Ce,Th)P04 is formed by the substitution of the Ce in monazite by Th. Numerous minerals can be formed by substitutions and provide a researcher sufficient degree of freedom to synthesize very complex minerals to produce useful CBPCs. 

Pyrolysis of nylon 6 generates a significant proportion of caprolactam, which can be considered the monomer. The cleavage of the peptide bond explains easily the formation of the monomer. The molecules of polymers have a spatial arrangement and do not have a linear form as typically indicated with planar chemical formulas (see also Section 1.3). The idealized spatial form for the molecule of nylon 6 is suggested below ... 

The (To data reported for materials having the same chemical formula are often very divergent. These differences can be partially due to temperature and electrolyte effects, namely both T and the nature of supporting electrolyte affect the (To, although their effects (discussed in subsequent sections) are not sufficiently significant to... 

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