Reaction mole interpretation

The decomposition kinetics of mercury fulminate [725] are significantly influenced by ageing, pre-irradiation and crushing these additional features of reaction facilitated interpretation of the observations and, in particular, the role of intergranular material in salt breakdown. Following a slow evolution of gas ( 0.1%) during the induction period, the accelerator process for the fresh salt obeyed the exponential law [eqn. (8)] when a < 0.35. The induction period for the aged salt was somewhat shorter and here the acceleratory process obeyed the cube law [eqn. (2), n = 3] and E = 113 kj mole-1. 

The kinetics of the polymerising system styrene-perchloric acid-methylene dichloride have been studied in the temperature range +19 °C to -19 °C, by a calorimetric technique. The propagation is pseudocationic, its rate constant at 19 °C is kp = 10.6 1 mole 1 s 1, and Ep = 11.6 kcal mole1. The elementary reactions are interpreted in detail by a mechanism involving an ester as chain carrier. 

The stoichiometry calculations of solution reactions can be done using the factor-unit method. The sources of the needed factors will be the mole interpretation of the reactions introduced as statement 2 in Section 5.9, and the molarities of the solutions involved in the reactions. Each known solution molarity will provide two factors. For example, the following two factors can be obtained based on a 0.400 M HCl solution ... 

The mechanism of the formation of (I) and (II) by debenzylation reaction was interpreted by Fles et al [3] as follows When one mole of aluminum halide is used it ionizes the covalent carbon-chloride bond and forms an ion pair (III) in which for steric reasons the CO residue cannot get close enough to its own sulfur to debenzylate it as easily as it can approach and debenzylate the sulfur of another molecule, thus forming poly-thiol-ester (II). 

At elevated temperatures (250-400°C) bromine reacts with thiazole in the vapor phase on pumice to afford 2-bromothiazole when equimolecu-lar quantities of reactants are mixed, and a low yield of a dibromothiazole (the 2,5-isomer) when 2 moles of bromine are used (388-390). This preferential orientation to the 2-position has been interpreted as an indication of the free-radical nature of the reaction (343), a conclusion that is in agreement with the free-valence distribution calculated in the early application of the HMO method to thiazole (Scheme 67) (6,117). 

First-order and second-order rate constants have different dimensions and cannot be directly compared, so the following interpretation is made. The ratio intra/ inter has the units mole per liter and is the molar concentration of reagent Y in Eq. (7-72) that would be required for the intermolecular reaction to proceed (under pseudo-first-order conditions) as fast as the intramolecular reaction. This ratio is called the effective molarity (EM) thus EM = An example is the nu-... 

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 ... 

Guldberg and Waage (1867) clearly stated the Law of Mass Action (sometimes termed the Law of Chemical Equilibrium) in the form The velocity of a chemical reaction is proportional to the product of the active masses of the reacting substances . Active mass was interpreted as concentration and expressed in moles per litre. By applying the law to homogeneous systems, that is to systems in which all the reactants are present in one phase, for example in solution, we can arrive at a mathematical expression for the condition of equilibrium in a reversible reaction. 

RDX. Gilpin Winkler (Ref 38b) measured a heat of nitration of — 88.0kcal/mole of hexa-mine for the reaction of hexamine with 97.5% nitric acid. They also obtained a value of — 140kcal/mole of hexamine for the formation of RDX from hexamine and Bachmann reagents (acetic anhydride, acetic acid, ammonium nitrate and nitric acid). Incidentally, Gilpin Winkler interpret their results to mean that hexamine dinitrate is an intermediate in the direct nitrolysis of hexamine to give RDX, while hexamine mononitrate is an intermediate in the Bachmann process of producing RDX... 

Torkar et al. [702,706—708] identified nucleation as an autocatalytic process at the (hk0) planes of hexagonal platelets of NaN3. The decelera-tory reaction fitted the first-order equation [eqn. (15)]. Values of E tended to be irreproducible for the pure salt E was about 180 kJ mole 1 but this was reduced to about half by doping. This influence of an additive and the observed similarities in magnitudes of E for decomposition and for diffusion were interpreted as indicating that growth of nuclei was controlled by a diffusion process. 

A note on good practice Enthalpies of formation are expressed in kilojoules per mole and enthalpies of reaction in kilojoules for the reaction as written. Note how the stoichiometric coefficients are interpreted as numbers of moles, and that an unwritten coefficient of 1 for urea is included as 1 mol in the calculation. 

The value of AG at a particular stage of the reaction is the difference in the molar Gibbs free energies of the products and the reactants at the partial pressures or concentrations that they have at that stage, weighted by the stoichiometric coefficients interpreted as amounts in moles ... 

This is Eq. 18 of Chapter 7.) We shall sometimes find it useful to interpret the n that appear in Eq. 3a as pure numbers (rather than amounts in moles), so that if n = 2 mol, in this convention we would use n = 2. To signal that we are using this molar convention ( molar because the units of AG then become kilojoules per mole), we attach a subscript r to AG (r for reaction) and write... 

The equilibrium constant in Eq. 2 is defined in terms of activities, and the activities are interpreted in terms of the partial pressures or concentrations. Gases always appear in K as the numerical values of their partial pressures and solutes always appear as the numerical values of their molarities. Often, however, we want to discuss gas-phase equilibria in terms of molar concentrations (the amount of gas molecules in moles divided by the volume of the container, [I] = j/V), not partial pressures. To do so, we introduce the equilibrium constant Kt., which for reaction E is defined as... 

The units of AG are joules (or kilojoules), with a value that depends not only on E, but also on the amount n (in moles) of electrons transferred in the reaction. Thus, in reaction A, n = 2 mol. As in the discussion of the relation between Gibbs free energy and equilibrium constants (Section 9.3), we shall sometimes need to use this relation in its molar form, with n interpreted as a pure number (its value with the unit mol struck out). Then we write... 

A note on good practice Equation 5 was derived on the basis of the "molar convention for writing the reaction Gibbs free energy that means that the n must be interpreted as a pure number. That convention keeps the units straight FE° has the units joules per mole, so does RT, so the ratio FE°/RT is a pure number and, with n a pure number, the right hand side is a pure number too (as it must be, if it is to be equal to a logarithm). 

The case of = 1 is a reasonable approximation for a great variety of cases, while = 0 covers another common situation where the reaction rate is limited by the disengagement of molecules from the surface. SIa has its usual interpretation as moles formed per unit volume of reactor per unit time when Ai is the... 

Specifically, it has recently been found 149) that diarylthallium tri-fluoroacetates may be converted into aromatic iodides by refluxing a solution in benzene with an excess of molecular iodine. Yields are excellent (74-94%) and the overall conversion represents, in effect, a procedure for the conversion of aromatic chlorides or bromides into aromatic iodides via intermediate Grignard reagents. The overall stoichiometry for this conversion is represented in Eq. (10), and it would appear that the initial reaction is probably formation of 1 mole of aromatic iodide and 1 mole of arylthallium trifluoroacetate iodide [Eq. (8)] which subsequently spontaneously decomposes to give a second mole of aromatic iodide and thallium(I) trifluoroacetate [Eq. (9)]. Support for this interpretation comes from the... 

The reaction was followed by means of the strong absorption of the Os(II) complex at 480 m/i. Unlike the Tl(riI) + Fe(II) system, there is a slight increase in rate as the hydrogen-ion concentration is increased. The kinetic data were interpreted on the basis that both Tl and TIOH react with Os(bipy)3 (with rate coefficients and respectively). At 24.5 °C and ju = 2.99 M, kj = 36.0 l.mole. see and= 14.7 l.mole sec corresponding activation energies are 6.90 and 11.5 kcal.mole" The latter values are considerably smaller than those for the T1(III) + T1(I) exchange and for the Tl(III)- -Fe(II) reaction . On the other hand, all three reactions are subject to retardation by Cl ions. 

Chemical reactivity differences may be calculated if for the transition state of a rate-determining step of a reaction a structural model can be given which is describable by a force field with known constants. We give only two examples. Schleyer and coworkers were able to interpret quantitatively a multitude of carbonium-ion reactivities (63, 111) in this way. Adams and Kovacic studied the pyrolysis of 3-homoadamantylacetate (I) at 550 °C and considered as transition state models the two bridgehead olefins II and III (112). From kinetic data they estimated II to be about 2 kcal mole-1 more favourable than III. 

Holroyd (1977) finds that generally the attachment reactions are very fast (fej - 1012-1013 M 1s 1), are relatively insensitive to temperature, and increase with electron mobility. The detachment reactions are sensitive to temperature and the nature of the liquid. Fitted to the Arrhenius equation, these reactions show very large preexponential factors, which allow the endothermic detachment reactions to occur despite high activation energy. Interpreted in terms of the transition state theory and taking the collision frequency as 1013 s 1- these preexponential factors give activation entropies 100 to 200 J/(mole.K), depending on the solute and the solvent. 

A very incisive set of experiments on Pd(lll) (16a) and Pt(lll) (16b) done in Gerhard Ertl s lab, show that the Eley-Rideal pathway makes no measurable contribution to the C0 production rate for many low pressure conditions. In these experiments, a steady-state CO pressure was established, the 0 pressure was modulated and the phase-lag of the modulated CO2 product signal was measured. The slope of In (tamj)), where 4> is the phase lag, as a function of T- can be interpreted in terms of an activation energy difference (Er - E ) between reaction and desorption. The result for Pt(lll) is -10.8 kcal mole- as shown in Figure 12 (16b). For an Eley-Rideal pathway in which a gas phase CO molecule makes a direct or impact attack on an oxygen adatom, E[Pg.51]

However, due to the difficulties in calculating ion yields in SIMS, quantitation of the data is not very reliable, and their work was not conclusive. We have determined here that the reaction of chemisorbed ethylene to form ethylidyne is first order in ethylene coverage. A noticeable isotope effect was observed, with activation energies of 15.0 and 16.7 Kcal/mole for C H and 02 respectively. These values are smaller than those calculated from TDS, but the differences can be reconciled by including the recombination of hydrogen atoms on the surface in the interpretation of the thermal desorption experiments. 

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