Gases, density stoichiometry

In order to probe some of these questions - an essential endeavor in forming a clear interpretation of our results - we wish to compare our experimentally-determined data with predictions from a simple model. The experimental data available (See Fig. 3) are instantaneous values of flame temperature from the N2 Stokes/anti-Stokes intensity ratio (plotted as histograms in Fig. 4) and simultaneously-obtained values of Nj density (determined from the absolute value of the N. Stokes intensity calibrated against the value obtained for N2 in ambient air). Accordingly, we have produced "comparison" plots using the following scheme (24) If we calculate flame gas density and temperature as a function of flame stoichiometry (i.e., as a function of the fuel/air equivalence ratio see Fig.7), then we can... 

The mass of gas needed to fill an air bag depends on the density of the gas. Gas density depends on temperature. To find the amount of gas generant to put into each system, designers must know the stoichiometry of the reactions and account for changes in temperature and thus the density of the gas. 

Many workers have used iodometric methods for the determination of concentrations of ozone in the range of several per cent by volume and higher. They have investigated the stoichiometry by comparison of the amounts of iodine liberated with the amounts of ozone determined by physical measurements of gas density or pressure change. Thus Lechner (5) found that both neutral and alkaline (0.2A potassium hydroxide) potassium iodide (0.2M) absorbed ozone efficiently and yielded the same amount of iodine, equivalent to one oxygen atom in the ozone molecule. This... 

It was pointed out that a bimolecular reaction can be accelerated by a catalyst just from a concentration effect. As an illustrative calculation, assume that A and B react in the gas phase with 1 1 stoichiometry and according to a bimolecular rate law, with the second-order rate constant k equal to 10 1 mol" see" at 0°C. Now, assuming that an equimolar mixture of the gases is condensed to a liquid film on a catalyst surface and the rate constant in the condensed liquid solution is taken to be the same as for the gas phase reaction, calculate the ratio of half times for reaction in the gas phase and on the catalyst surface at 0°C. Assume further that the density of the liquid phase is 1000 times that of the gas phase. 

In some specific cases one would like to convert the chemisorption data into an averaged particle size. In that case, the number of surface atoms per unit surface area (density of surface atoms) is an essential parameter. Since this number depends on the type of the crystallographic plane, (see Table 3.7), one also needs information on the types of crystallographic planes exposed to the gas phase. This is also important for another reason the adsorption stoichiometry may depend on the crystallographic plane. 

The pressure dependence, as before, is derived not only from the perfect gas law for p, but from the density-pressure relationship in Z as well. Also, the effect of the stoichiometry of a reacting gas mixture would be in Z. But the mole fraction terms would be in the logarithm, and therefore have only a mild effect on the induction time. For hydrocarbon-air mixtures, the overall order is approximately 2, so Eq. (7.46) becomes... 

The atmosphere is also important in sintering. Gas trapped in closed pores will limit pore shrinkage unless the gas is soluble in the grain boundary and can diffuse from the pore. Alumina doped with MgO can be sintered to essentially zero porosity in hydrogen or oxygen atmospheres, which are soluble, but not in air, which contains insoluble nitrogen. The density of oxides sintered in air is commonly less than 98% and often only 92-96%. The sintering atmosphere is also important in that it may influence the sublimation or the stoichiometry of the principal particles or dopants. 

The presence of H- in metallic lanthanide hydrides was proposed by Dialer (9), and the idea later extended to other metallic hydrides (11, 23). As at present interpreted the model suggests that H is associated with a helium-like configuration of electrons, in a rather low-density electron sea. The metal is considered to be the inert-gas core (or a stable non-inert-gas core) with a localized net positive charge derived from the stoichiometry of the hydride. The remaining electrons of the metal are considered to be in the usual directed hybrid orbitals, whose directions help determine the crystal structure and whose bonding to nearest metal neighbors stabilizes the structure. Electrons in these directed orbitals are sufficiently delocalized to provide a conduction band and metallic or semimetallic properties. [Compare the model of TiO and VO proposed by Morin (29).]... 

Table 11.1. Physical properties of hydrocarbon films deposited with a remote electron cyclotron resonance plasma from three different C2Hz source gases at three different dc self-bias voltages 1% np represents the parallel component of the real part of the refractive index as measured by in situ ellipsometry. The film composition is obtained from ion-beam analysis. The total particle number densities nc and n-H are calculated from the stoichiometry and the film thickness. Deposition parameters pressure p = 0.2 Pa adjusted with gas flow at constant pumping speed, absorbed microwave power density P = 10 kW nT3 [17]...

Mixed y-Ga203-Al203 oxides of different stoichiometry were prepared by the solvothermal method from Ga(acac)3 and Al(OPr-i)3 as starting materials and were used as catalysts for selective reduction of NO with methane. The initial formation of gallium oxide nuclei controls the crystal structure of the mixed gallium-aluminum oxides. It is found that the acid density per surface area is independent of the Al Ga feed ratio but depends on the reaction medium (diethylenetriamine, 2-methylaminoethanol, toluene, 1,5-pentanediol etc.), whereby in diethylenetriamine the catalyst had lower densities of acid sites and showed a higher methane efficiency. 

For liquid droplets, requirement (1) typically means that the spray must be dilute (that is, the ratio of the volume occupied by the condensed phase to the volume occupied by the gas must be small) because collisions tend to be frequent when the volume of particles per unit volume of space becomes too large. Since the mass density of the particles greatly exceeds that of the gas in many sprays and the stoichiometry of most hydrocarbon-oxidizer systems is such that the mass of the fuel is considerably less than that of the gaseous oxidizer in stoichiometric mixtures, the hypothesis of a dilute spray often is valid in hydrocarbon spray combustion. 

The main characteristics of the green mixture used to control the CS process include mean reactant particle sizes, size distribution of the reactant particles reactant stoichiometry, j, initial density, po size of the sample, D initial temperature, Tq dilution, b, that is, fraction of the inert diluent in the initial mixture and reactant or inert gas pressure, p. In general, the combustion front propagation velocity, U, and the temperature-time profile of the synthesis process, T(t), depend on all of these parameters. The most commonly used characteristic of the temperature history is the maximum combustion temperature, T -In the case of negligible heat losses and complete conversion of reactants, this temperature equals the thermodynamically determined adiabatic temperature (see also Section V,A). However, heat losses can be significant and the reaction may be incomplete. In these cases, the maximum combustion temperature also depends on the experimental parameters noted earlier. 

In both explosives and propellants the materials are relatively non-porous. The binders and plasticizers used effectively fill the pore spaces. Pyrotechnics are porous and the heat transfer related to the hot gas permeation into the reactant material mixture becomes important. In many pyrotechnics no binders or plasticizers are used. The explosives and propellants have burning (or detonation) rates that depend on density, temperature, and pressure. However, the burning rates of pyrotechnics are, in addition, affected by porosity, particle sizes, purity, homogeneity (degree of mixing), and stoichiometry (fuel or oxidizer ratio). 

The lower CO2 selectivity observed on small pellets (Table V) apparently reflects the transport-limited removal of water, a product of the FT synthesis. CO2 selectivity also increases with increasing site density, CO conversion, and water concentration in the catalyst bed this suggests that CO2 forms in secondary water-gas shift reactions that become significant as intrapellet water fugacities rise because of transport restrictions. Transport rates of CO and H2O in hydrocarbon liquids are qualitatively similar and the reaction stoichiometry requires that one water molecule must be removed... 

Unfortunately the materials do not have a sufficiently well-developed rubbery modulus for use in calculations. One therefore resorts to the equivalent ultimate Maxwell element from which the maximiun relaxation time was computed, and utilizes the modulus corresponding to that ultimate element for subsequent computations. Now if La" " " ions act as crosslinks, then the values should be directly proportional to their concentration, c, since both and c are inversely proportional to the molecular weight between crosslinks. Mg. The former relationship is due to the kinetic theory of rubber elasticity (E = 03qRTIMc where 0 is the front factor, q is the density, and R the gas constant), and the latter to simple stoichiometry (c = g/2Mj) for tetrafunctional crosslinks. A plot of vs. c was shown in Fig. 9, both for La" " " " and for Ca++ indicating that both ions act as crosslinks, at least at low concentrations and only for the ultimate Maxwell element. 

There are ways other than density to include volume in stoichiometry problems. For example, if a substance in the problem is a gas at standard temperature and pressure (STP), use the molar volume of a gas to change directly between volume of the gas and moles. The molar volume of a gas is 22.41 L/mol for any gas at STP. Also, if a substance in the problem is in aqueous solution, then use the concentration of the solution to convert the volume of the solution to the moles of the substance dissolved. This procedure is especially useful when you perform calculations involving the reaction between an acid and a base. Of course, even in these problems, the basic process remains the same change to moles, use the mole ratio, and change to the desired units. 

A stainless steel reaction vessel of 10 cc volume was charged with 0.56 part sodium nitrite, 0.8 part of distilled water and 0.34 part sodium bicarbonate. The vessel was cooled with liquid nitrogen under a blanket of argon to assure lack of air moisture condensation in the vessel. To the chilled vessel was added 3.9 parts of liquid methyl chloride (measured and weighed at—77° C. with density taken at 1.1). 3.5 parts of the added methyl chloride was excess over that required for stoichiometry. The vessel was sealed and heated at 75° C. for 4 hours with agitation. The resultant material was analyzed by conventional gas chromatographic analysis and showed that nitromethane was obtained in 57 percent yield. The selectivity to nitromethane was 74 percent based on the sodium nitrite. 

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