Volume change of reaction

Table 2.5 shows the thermodynamic behavior of the water ionization reaction. The variation of log Kjy and AG (molal scale for ions, mole fraction scale for water) with temperature at a fixed pressure of 1 atm and the variation of these quantities with pressure at 25°C are given. These data can be used to obtain the enthalpy change of reaction, AH, and the volume change of reaction, AV. ... 

There are two central questions in chemical kinetics (1) How fast can the fastest chemical reactions be (2) Why are many chemical reactions slow We will try to provide some elementary insights when answering these questions. Kinetics has several levels. First, there is a level of correct stoichiometry for a reaction. Second, there is a level of energetic characterization of a reaction, that is, free energy, enthalpy, entropy, and volume changes of reaction (see Section 2.4 and Table 2.6). Third, there is a level of experimental study of reaction rates and the formulation of rate laws that correctly describe the observed rates. Finally, there is the level of mechanism, where elementary reaction steps are proposed, verified experimentally, and used to predict rate expressions, which are then compared with observation. 

The symbols most characteristic of the De Donder school are r j, rrp y and Arp, denoting respectively the heats of reaction at constant pressure and constant volume (with the old thermochemical convention that heat evolved is positive), and the volume change of reaction at constant T and p. These symbols have been discarded and we employ... 

The picture arrived at after exhaustive research with luminous bacteria, and eventually discussed at length with reference to many other types of biological processes, involved molecular volume changes of activation in the enzyme reaction and volume changes of reaction in the reversible denaturation of the protein moiety. Continued research concerning the... 

Thus, fractionation is mostly dependent on temperature. Since isotopes differ only in their nucleus, the volume change of Reaction (1) is very small. From the relation 5G = -S5T + V5P, it follows that there is generally little or no measurable effect of pressure on fractionation (Clayton et al. 1975, Polyakov and Kharlashima 1994 Chacko et al., this volume). 

For reactions in solntion an additional thermodynamic property that can be helpful is available. The effect of pressure on the equilibrium constant of a reaction yields the volume change of reaction, AT, given by Equation 1.28. 

Relative volume change of reaction mixture due to complete conversion of rate determining reactant Common index for reactions... 

The pressure-jump (P-jump) method is based on the pressure dependence of the equilibrium constant, Eq. (4-28), where AV is the molar volume change of the reaction. 

Example 2.11 Suppose initially pure A dimerizes, 2A —> B, isothermally in the gas phase at a constant pressure of 1 atm. Find a solution to the batch design equation and compare the results with a hypothetical batch reactor in which the reaction is 2A B - - C so that there is no volume change upon reaction. 

Due to the AV (volume change of activation) of Claisen rearrangements having a negative value, as in the Diels-Alder reactions, the Claisen rearrangement reaction is expected to be accelerated by water according to the same effect.151,152... 

Potential volume change of cement—aggregate combinations Accelerated detection of potentially deleterious expansion of mortar bars due to alkali-silica reaction... 

Volume of reaction mixture per kg of reaction mixture (assuming no volume change of solution)... 

Volume changes on reaction may be neglected. At 25 °C the reaction rate constant is equal to 9.92 x 10 3 m3/kmole sec. If one employs a well-stirred isothermal batch reactor to carry out this reaction, determine the holding time necessary to achieve 95% conversion of the limiting reagent using initial concentrations of 0.1 and 0.08 kmole/m3 for cyclopentadiene and benzoquinone, respectively. 

From the units on the reaction rate constant, the reaction is second order. There is a volume change on reaction and S = —1/2. Thermal expansion will also occur, so equations 3.1.44 and 3.1.46 must be combined to get the reactant concentrations. Since equimolar concentrations of reactants are used, the design equation becomes... 

In most photoacoustic experiments, it has been generally assumed that the experimental volume change resulted only from the thermal deposition of energy to the solvent. In such cases, the ratio of the volume change of the sample to that of the reference compound, a, could be related to the enthalpy of reaction... 

At high substrate concentration then, the observed overall volume change will be more or less equal to the volume change of the ratedetermining step. If AV31 > 0, this step will be even more ratedetermining at higher pressure, as seen from Eq. (53). If AVS < 0, the reaction rate will increase with pressure in a certain pressure in-... 

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