Stoichiometry stoichiometric numbers

STOICHIOMETRIC NUMBER Stoichiometry of elementary reactions, CHEMICAL KINETICS MOLECULARITY UNIMOLECULAR BIMOLECULAR TRANSITION-STATE THEORY ELEMENTARY REACTION STOKE S SHIFT... 

The slope of the plot is a function of the reaction stoichiometry although the functional dependence is complicated. In addition, the thermodynamic point, i.e., the point which corresponds to Keq (which is at 1 X 10"5 for all curves given here) does not correspond to the point of inflection, and even for the simplest case, dimerization, the point of inflection does not correspond to the midpoint. In addition, the curves are not symmetrical about the midpoint. Thus, no simple analysis of curve shape based on midpoint value or inflection point can give the thermodynamic or stoichiometric numbers. 

Here the stoichiometric number of methane is —2, ethylene —1, butane +1, and hydrogen +1. If we look at the change in the number of moles of one component, there is a direct relationship between stoichiometry and the change in the number of moles of any other component. 

Each of the reactions (r) contributing to the overall metabolic activity has a characteristic molar enthalpy, A,//b (J moL1), where subscript B indicates that any given reaction stoichiometry must be divided by vB (v = stoichiometric number) to give a stoichiometric form of unity (IVbI = 1). Each is calculated from the balanced reaction stoichiometry and enthalpy of formation. If this value is multiplied by the measured chemical reaction flux, JB (mol s 1 m-1), then the reaction enthalpy flux, JhO mo -3), is obtained,... 

The reaction (1.3) above is a statement of the stoichiometry, and reports the stoichiometric numbers, v, which take values ... 

Metabolic fluxes are responsible for maintaining the homeostatic state of the cell. This condition may be translated into the assumption that the metabolic network functions in or near a non-equilibrium steady state (NESS). That is, all of the concentrations are treated as constant in time. Under this assumption, the biochemical fluxes are balanced to maintain constant concentrations of all internal metabolic species. If the stoichiometry of a system made up of M species and N fluxes is known, then the stoichiometric numbers can be systematically tabulated in a... 

The optimum stoichiometry corresponds to [Li+Cg vS], where v is the stoichiometric number for co-intercalated solvent molecules S. The overall reaction is... 

The overall equation of the last scheme is obtained from the overall equation of the previous one when it is multiplied by 1/2. Such an operation is senseless for the equations of simple stages, if the reaction Z +1/202 <- ZO does not occur. The reaction /l 02 +S02=S03 describes only stoichiometry, but not the reaction mechanism. A set of stoichiometric numbers of the stages producing an overall reaction equation is called after Horiuti a "reaction route". Routes must be essentially different and it is impossible to obtain one route from another through multiplication by a number, although their respective overall equations can be identical. 

Stoichiometry Stoichiometric—Referring to exact balance of weights of materials in a reacting mixture, based on the stipulations of the Daltonide compounds in which each molecule contains atoms in proportions of small whole numbers. Opposite—nonstoichio-metric or BertholUde compounds. 

The first step is to write both compounds of the redox couple and when necessary to adjust the stoichiometric numbers, in order to ensure that the element with the variable oxidation number is preserved. The number of electrons exchanged is then determined from the difference between the oxidation numbers of the element in its oxidized and reduced states, taking into account the stoichiometry. Protons are added if necessary to ensure that the sum of the charges on both sides of the overall equation are kept the same. Finally, water molecules H2O are added to balance the oxygen (or hydrogen) element. It is then possible to check if the hydrogen (or oxygen) element is also balanced in the overall equation. 

Let us consider the mechanism of the electrode process as a sequence of elementary reactions all of which, in a steady state, occur at the same velocity, equal to the overall velocity, when stoichiometry is properly taken into account. Let us designate by j the rate-determining step and let us assume that it occurs yj times during one occurrence of the overall process. The number yj is the stoichiometric number of step j. Let us consider the system as being in a state close to electrochemical equilibrium for which it can safely be assumed that the electrochemical affinities of all other... 

Add the components ethanol, diethylamine, triethylamine, and water to the reaction. Make the stoichiometric coefficients -1 for ethanol and dieth-lyamine (because they are being consumed) and 1 for both triethylamine and water (because they are being produced with a stoichiometry of 1). The forward order is automatically defaulted to the stoichiometric number 1 for this case, it is different than how we defined our reaction data. Assume no reverse reactions. Change the reaction order to 2 with respect to ethanol and 0 with respect to diethylamine for the forward reaction order. Since the reaction is irreversible, under Rev Order, type zero for all components. 

In principle, Chen, given the flux relations there is no difficulty in constructing differencial equations to describe the behavior of a catalyst pellet in steady or unsteady states. In practice, however, this simple procedure is obstructed by the implicit nature of the flux relations, since an explicit solution of usefully compact form is obtainable only for binary mixtures- In steady states this impasse is avoided by using certain, relations between Che flux vectors which are associated with the stoichiometry of Che chemical reaction or reactions taking place in the pellet, and the major part of Chapter 11 is concerned with the derivation, application and limitations of these stoichiometric relations. Fortunately they permit practicable solution procedures to be constructed regardless of the number of substances in the reaction mixture, provided there are only one or two stoichiomeCrically independent chemical reactions. 

Quantitative Calculations In acid-base titrimetry the quantitative relationship between the analyte and the titrant is determined by the stoichiometry of the relevant reactions. As outlined in Section 2C, stoichiometric calculations may be simplified by focusing on appropriate conservation principles. In an acid-base reaction the number of protons transferred between the acid and base is conserved thus... 

It is not necessary for a compound to depart from stoichiometry in order to contain point defects such as vacant sites on the cation sub-lattice. All compounds contain such iirndirsic defects even at the precisely stoichiometric ratio. The Schottky defects, in which an equal number of vacant sites are present on both cation and anion sub-lattices, may occur at a given tempe-ramre in such a large concentration drat die effects of small departures from stoichiometry are masked. Thus, in MnOi+ it is thought that the intrinsic concentration of defects (Mn + ions) is so large that when there are only small departures from stoichiometry, the additional concentration of Mn + ions which arises from these deparmres is negligibly small. The non-stoichiometry then varies as in this region. When the departure from non-stoichio-... 

Stoichiometry in Reactive Systems. The use of molar units is preferred in chemical process calculations since the stoichiometry of a chemical reaction is always interpreted in terms of the number of molecules or number of moles. A stoichiometric equation is a balanced representation that indicates the relative proportions in which the reactants and products partake in a given reaction. For example, the following stoichiometric equation represents the combustion of propane in oxygen ... 

Sometimes we need to know how much product to expect from a reaction, or how much reactant we need to make a desired amount of product. The quantitative aspect of chemical reactions is the part of chemistry called reaction stoichiometry. The key to reaction stoichiometry is the balanced chemical equation. Recall from Section H that a stoichiometric coefficient in a chemical equation tells us the relative amount (number of moles) of a substance that reacts or is produced. Thus, the stoichiometric coefficients in... 

A number of selenium and tellurium compounds of the presently discussed metals show a quite different behavior from the Fe-S system. Iron and selenium form two compounds FeSe with a broad stoichiometry range and FeSe2 with a much narrower composition field. Below 400 the non-stoichiometric Fei xSe exists by creation of iron vacancies and can have compositions lying between FeySes and Fe3Se4. At low temperatures there exist two phases an a (PbO type) and a f) (NiAs type) phase. The crystal sUiicture of the diselenide, FeSe2, is an orthorhombic, C18 (marcasite) type. In the Fe-Te system, the defect NiAs structure is found at a composition close to FeTei.s, as about one-third of the Fe atoms are missing. At compositions around FeTe the behavior is complex, and the f)-phase has the PbO structure (like FeSe) but with additional metal atoms (i.e., FeuTe). 

Stoichiometry (from the Greek stoikeion—element) is the practical application of the law of multiple proportions. The stoichiometric equation for a chemical reaction states unambiguously the number of molecules of the reactants and products that take part from which the quantities can be calculated. The equation must balance. 

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