Conductivity, equivalent molecular

Among the two-terminal devices that can be imagined for UE [capacitors, inductors, rectifiers, negative differential resistance (NDR) devices], the simplest is a molecular wire, that is, a molecule capable of conducting electricity a nanoconductor or, equivalently, a nanoresistor. Even the most conductive of molecular wires has a minimum resistance. 

In order to recognize the patterns that pervade carborane chemistry, it is instructive to conduct a molecular census, to ascertain where and in what coordination-number environments the various groups, e.g., BH, BHj, CH, CHg, CHj, and Lewis base equivalents (B LB, BH LB, and BH2 LB, where LB = Lewis base) are most frequently found. Table II itemizes the various groups obvious trends may be observed and examples of the extreme cases are given. 

Equations (40 to 48) thus provide a complete simple model for molecular conduction, equivalent to similar approximations used in theories of molecular... 

The probability matrix plays an important role in many processes in chemical physics. For chemical reactions, the probability of reaction is often limited by tunnelling tlnough a barrier, or by the fonnation of metastable states (resonances) in an intennediate well. Equivalently, the conductivity of a molecular wire is related to the probability of transmission of conduction electrons tlttough the junction region between the wire and the electrodes to which the wire is attached. 

Laminar Flow Normally, laminar flow occurs in closed ducts when Nrc < 2100 (based on equivalent diameter = 4 X free area -i-perimeter). Laminar-flow heat transfer has been subjected to extensive theoretical study. The energy equation has been solved for a variety of boundaiy conditions and geometrical configurations. However, true laminar-flow heat transfer veiy rarely occurs. Natural-convecdion effects are almost always present, so that the assumption that molecular conduction alone occurs is not vahd. Therefore, empirically derived equations are most rehable. 

The discussion of molecules and molecular ions will be continued in Sec. 29. Here we shall begin the detailed examination of solutes that are completely dissociated into ions. The conductivity of aqueous solutions of such solutes has been accurately measured at concentrations as low as 0.00003 mole per liter. Even at these concentrations the motions of the positive and negative ions are not quite independent of each other. Owing to the electrostatic forces between the ions, the mobility of each ion is slightly less than it would be in a still more dilute solution. For example, an aqueous solution of KC1 at 25°, at a concentration of 3.2576 X 10 6 mole per liter, was found to have an equivalent con-... 

HOMO = highest occupied molecular orbital) is the Fermi limit. Whenever the Fermi limit is inside a band, metallic electric conduction is observed. Only a very minor energy supply is needed to promote an electron from an occupied state under the Fermi limit to an unoccupied state above it the easy switchover from one state to another is equivalent to a high electron mobility. Because of excitation by thermal energy a certain fraction of the electrons is always found above the Fermi limit. 

Fig. 14 The three-branches dianthra[a,c]naphtacene molecule circuit of symmetry formed by three anthracene fragments equivalently bonded to a central phenyl group. The molecule is adsorbed by the three branch ending phenyls onto the Au nano-pads. A semilogarithmic plot of the Tij(E) EHMO-NESQC electron transmission spectra (in valence energy range) per pair of branches. The presented frontier MOs show how the valence n electrons are delocalized on the molecule. At resonance, this provides a good electronic conductance through each pair of molecular branches, almost one quantum of conductance...

Nitrogen is analyzed by GC using a thermal conductivity detector and a molecular sieve, SA or equivalent column, and helium as the carrier gas. Its presence may be confirmed by mass spectrometry. The characteristic mass ion for GC/MS identification of N2 is 28. 

As an example of this, consider the three compounds obtained from hexammino-eobaltie chloride by replacing ammonia by nitrito-groups. The same total number of acidic radicles is retained in the molecule, but the derivatives differ in electrical conductivity in equivalent solutions. The molecular conductivity of hexammino-eobaltie chloride at 25° C. and 1000 litres dilution is 431-6 of the mononitrito-derivative, [Co(NH3)5(N02)]C12, is 246-4 of the di-derivative, [Co(NH3)4(N02)2]C1, is 98-83 and of the trinitrito-derivative, [Co(NH3)3(N02)3], is zero, this being a non-electrolyte. Further substitution transforms the complex from cation to anion thus [Co(NH3).2(N02)4]K. 

Solution This problem is really no different from the molecular weight determinations of unknown acids that are often conducted in general chemistry lab courses. What is important to recognize is that there is one carboxyl group per molecule or one equivalent per mole. Therefore the molecular weight of the polymer is given by... 

Percentage concentration. Equivalents per litre. Specific resistance. Specific conductivity. Molecular conductivity. Percentage ionization. 

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