Stoichiometry stoichiometric ratio

Stoichiometry is the composition of the air-fuel mixture required to obtain complete combustion. The stoichiometric ratio, r, is the quotient of the respective masses, and m, of air and fuel arranged in the stoichiometric conditions ... 

If one imagine.s that the fuel is used in the liquid state in the form of droplets —as in the case of fuel injection— the specific energy of the motor fuel (SE) is expressed in kilojoules per kilogram of air utilized, under predetermined conditions of equivalence ratio (stoichiometry for example). The SE is none other than the NHY /r quotient where r represents the previously defined stoichiometric ratio. 

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-... 

All changes are related by stoichiometry. Each ratio of changes in amount equals the ratio of stoichiometric coefficients in the balanced equation. In the example above, the changes in amounts for H2 and N2 are in the ratio 3 1, the same as the ratio for the coefficients of H2 and N2 in the balanced equation. 

Based on the fact that pi-acids interact with the trinuclear gold] I) pi-bases, TR(carb) and TR(bzim), the trinuclear 3,5-diphenylpyrazolate silver(I) complex was reacted with each. Mixing [Au3(carb)3] or [Au3(bzim)3] with [Ag3(p,-3,5-Ph2pz)3] in CH2CI2 in stoichiometric ratios of 1 2 and 2 1 produced the mixed metal/mixed ligand complexes in the same gold-silver ratios. The crystalline products were not the expected acid-base adducts. It is suspected that the lability of the M-N bond (M=Au, Ag) in these complexes results in the subsequent cleavage of the cyclic complexes to produce the products statistically expected from the stoichiometry of materials used [74]. As a result of the lability of Au-N and Ag-N bonds, and the stability of... 

When the drug entity is capable of forming complexes that have higher stoichiometric ratios than 1 1, the construction of equilibrium constant expressions becomes more difficult. For the general case of m.n stoichiometry, as defined by... 

In some instances, this approach has proven successful, with comparatively low crystallization temperatures being observed. For example, Eichorst and Payne in the synthesis of LiNb03 noted crystallization temperatures of 400-500 °C for a mixed-metal alkoxide precursor.111 In other instances, these attempts have proven less successful. Numerous attempts have been made to synthesize Pb-Zr and Pb-Ti precursors, each with the 1 1 cation stoichiometry of the desired PbZr03 and PbTi03 compounds.83,84 Unfortunately, 1 1 stoichiometric ratio compounds have not always been obtained, with crystalline compounds of other stoichiometries precipitating from the solution, as illustrated in Fig. 2.11.83 This figure shows the crystal structure of PbTi2[p(4)—... 

For the calculation of a mono-protic acid with a mono-basic base, the stoichiometry is simply 1 1 because 1 mol of acid reacts with 1 mol of base. We say the stoichiometric ratio s = l. The value of s will be two if sulphuric acid reacts with NaOH since 2 mol of base are required to react fully with 1 mol of acid. For the reaction of NaOH with citric acid, s = 3 and s = 4 if the acid is H4EDTA. 

Considering then the phase composition as a significant parameter, we obtain the histogram shown in Fig. 7.1(a) for the distribution of the intermetallic phases according to the stoichiometry of binary prototypes. For instance, the binary Laves phases, the A1B2, Caln2, etc., type phases are all included in the number reported for the 66-67.99 stoichiometry range, even if the real stoichiometry of the specific phase is different, see Fig. 7.1(b). We may note the overall prevalence of phases and, to a certain extent, of structural types, which may be related to simple (1 2, 1 1, 1 3, 2 3, etc.) stoichiometric ratios. 

With reference to their ideal stoichiometries a few ubiquitous crystal structure prototypes will be presented in the following. Attention will be especially given to some structures corresponding to simple stoichiometric ratios. Notice however that, in several cases, a given prototype may be represented by a point compound but also,... 

Though it is impossible to formulate a complete mathematical representation of the super-rate burning, it is possible to introduce a simplified description based on a dual-pathway representation of the effects of a shift in stoichiometry. Generalized chemical pathways for both non-catalyzed and catalyzed propellants are shown in Fig. 6.26. The shift toward the stoichiometric ratio causes a substantial increase in the reaction rate in the fizz zone and increases the dark zone temperature, a consequence of which is that the heat flux transferred back from the gas phase to the burning surface increases. 

Since rocket propellants are composed of oxidizers and fuels, the specific impulseis essenhally determined by the stoichiometry of these chemical ingredients. Ni-tramines such as RDX and HMX are high-energy materials and no oxidizers or fuels are required to gain further increased specific impulse. AP composite propellants composed of AP particles and a polymeric binder are formulated so as to make the mixture ratio as close as possible to their stoichiometric ratio. As shown in Fig. 4.14, the maximum is obtained at about p(0.89), with the remaining fraction being HTPB used as a fuel component. 

X 107 M 11 for a 1 1 stoichiometric ratio. Two affinity complexes were separated. One complex was identified by the Scatchard method as having a 1 1 stoichiometric ratio (complex 1). The other complex (complex 2) is proposed to have a stoichiometry with an excess of anti-BSA to BSA, ... 

From this one can deduce an ideal stoichiometric ratio of C1 to B1, or MO2 to Ln203. In general, the observed stoichiometry differs from the ideal value, indicating incomplete... 

A grey-blue compound of stoichiometry Ni(CN)2-1.5H20 is formed by the reaction of NiS04 and KCN in stoichiometric ratio in boiling water. In this polymeric compound the bridging CN... 

The distinction between substrate and ligand is arbitrary, and is made solely for experimental convenience. Normally, stoichiometric ratios are expressed in the order substrateligand, so that 1 2 stoichiometry denotd5L2, 2 1 mean L, and so on. 

A reaction is said to be stoichiometric when the fuel and oxygen consume each other completely, forming carbon dioxide (C02) and water (H20) under ideal conditions. The equivalence ratio is the parameter relating a mixture proportion to stoichiometry. It is defined as the ratio of fuel-to-oxygen amounts times the stoichiometric ratio of oxygen-to-fuel amounts. If there is an excess of fuel, then the mixture is called fuel-rich or rich, and the equivalence ratio is greater than 1, and if there is an excess of oxygen, then it is called fuel-lean or lean and the equivalence ratio is less than 1. 

For the designer, understanding the mass balance of the plant is a key requirement that can be fulfilled only when the reactor/separation/recycle structure is analyzed. The main idea is that all chemical species that are introduced in the process (reactants, impurities) or are formed in the reactions (products and byproducts) must find a way to exit the plant or to be transformed into other species [4]. Usually, the separation units take care that the products are removed from the process. This is also valid for byproducts and impurities, although is some cases inclusion of an additional chemical conversion step is necessary [5, 6]. The mass balance of the reactants is more difficult to maintain, because the reactants are not allowed to leave the plant but are recycled to the reaction section. If a certain amount of reactant is fed to the plant but the reactor does not have the capacity of transforming it into products, reactant accumulation occurs and no steady state can be reached. The reaction stoichiometry sets an additional constraint on the mass balance. For example, a reaction of the type A + B —> products requires that the reactants A and B are fed in exactly one-to-one ratio. Any imbalance will result in the accumulation of the reactant in excess, while the other reactant will be depleted. In practice, feeding the reactants in the correct stoichiometric ratio is not trivial, because there are always measurement and control implementation errors. 

A titration curve may for convenience be considered to consist of three portions the region before the equivalence point, the equivalence point, and the region beyond the equivalence point. At all points except at the beginning before any titrant has been added, two redox couples are present, corresponding to the sample and the titrant. In the region before the equivalence point, the potential is calculated conveniently from the known concentration ratio of the sample redox couple. After the equivalence point the concentration ratio of the titrant redox couple is known from the stoichiometry. At the equivalence point both the sample and titrant redox couples are present in the stoichiometric ratio. 

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