Equilibrium constants tabulated data

A 3rd law analysis of the experimental equilibrium constants tabulated by Cotton and Jenkins (3 ) using current JANAF auxiliary data (4) leads to Dq = 204.8 kcal mol which is 2.6 kcal raol higher than the 202.2 kcal mol derived by Cotton and Jenkins (3 ). Applying this difference to the data of Ryabova and Gurvich ( ) and of Sugden and Schofield (2) as recalculated by... 

Equimolal proportions of the reactants are used. Thermodynamic data at 298 K are tabulated. The specific heats are averages. Find (1) the enthalpy change of reaction at 298 and 573 K (2) equilibrium constant at 298 and 573 K (3) fractional conversion at 573 K. 

Steps 1 and 2 require thermodynamic data. Eigure 2-1 shows the equilibrium constants of some reactions as a function of temperature. The Appendix at the end of this chapter gives a tabulation of the standard change of free energy AG° at 298 K. 

Examples 7.12 and 7.13 treated the case where the kinetic equilibrium constant had been determined experimentally. The next two examples illustrate the case where the thermodynamic equilibrium constant is estimated from tabulated data. 

Equation is extremely important because it links thermodynamic data with equilibrium constants. Recall that Equation makes it possible to use tabulated values for A Gj to calculate the value for A G ° for many reactions ... 

Table 5 lists equilibrium data for a new hypothetical gas-phase cyclisation series, for which the required thermodynamic quantities are available from either direct calorimetric measurements or statistical mechanical calculations. Compounds whose tabulated data were obtained by means of methods involving group contributions were not considered. Calculations were carried out by using S%g8 values based on a 1 M standard state. These were obtained by subtracting 6.35 e.u. from tabulated S g-values, which are based on a 1 Atm standard state. Equilibrium constants and thermodynamic parameters for these hypothetical reactions are not meaningful as such. More significant are the EM-values, and the corresponding contributions from the enthalpy and entropy terms. 

CH3COCH3 + HCN . (CH3)2C0.CN.0H, A + B C was studied in aqueous solution (Svirbely Roth, JACS 75 3109, 19531. In one run with initial concentrations of 0.0758 normal for HCN and 0.1164 normal for acetone, the tabulated data were obtained. The equilibrium constant was Ke = 13.87. Find the specific rate. 

As demonstrated by the association rate constants listed in Table 10, association is relatively fast and has low activation energies. Table 10 also tabulates the equilibrium constants for reaction of a variety of nucleophiles with carbenium ions. Most of the equilibrium constants involving trityl carbenium ions were obtained from UV studies, whereas those of me-thoxymethylium carbenium ions with both dimethyl ether and methylal were calculated using dynamic NMR [64]. Values for isobutoxy alkyl derivatives have been estimated from polymerization kinetics. The data presented in Table 10 demonstrate that the equilibrium constants are lower for weaker nucleophiles and more stable carbenium ions. For example, carbenium ions react faster with diethyl ether than with the less nucleo-... 

For the related tautomerism between the higher homologues, 1,3,5-cyclooctatriene (120) and bicy-clo[4.2.0]octa-2,4-diene (121), a tabulation of a series of derivatives including thermodynamic data is presented in the treatise by Marvell. The data reveal a large variation in equilibrium constants by introducing seemingly small changes in the structure. While the electronic effects of the substituents at C-7... 

To compute equilibrium constants at different temperatures and pressures from tabulated standard thermodynamic data. 

Clearly, the user of any thermodynamic tables must become familiar with the tables and the interrelationships of the data if he plans to make extensive use of the values. Moreover, he must not use them blindly. The actual numbers tabulated for the different thermodynamic functions are not so significant as the final equilibrium constants that are to be calculated from them. These tables are designed to yield equilibrium constants of as high an accuracy as can be obtained from the available data. Thus, the uncertainty of a given heat of sublimation may be considerably smaller in regard to its use for calculation of vapor pressures than in regard to its use for heat balance calculations. 

The reverse rate constants for the elementary reactions used in the present work were caJculated from the forward rate constants and the equilibrium constant by assuming microscopic reversibility. Standard states used in tabulations of thermodynamic data are invariably at 1 atm and the temperature of the system. Since concentration units were required for rate constant calculations, a conversion between Kp and Kc was necessary. Values of Kp were taken from the JANAF Thermochemical tables (1984). Kc was calculated from the expression ... 

The dimensionless quantity K is the thermodynamic equilibrium constant, which Section 14.3 shows can be calculated from tabulated data on the products and reactants, even if the empirical equilibrium constant defined in Equation 14.1b is not known. Therefore, K is the preferred tool for analyzing reaction equilibria in general. The informal argument by which we replaced ICp with K is made rigorous... 

The convention we follow in this book, already stated in Section 14.2, is to describe chemical equilibrium in terms of the thermodynamic equilibrium constant K and to emphasize the fact that K can be obtained easily from tabulated thermodynamic data. Following this convention, the mass action law for a general reaction involving ideal gases is written as... 

The values are from the equation which best fit the data of Johnson (1982). His values for koH Kw are reinterpreted as indicated in Emerson (1995). The equilibrium constants necessary to calculate the reverse rate constants are also tabulated. Where two values are presented in column 1 the first is for fresh water (I = 0) and the second is for seawater. The exponential notation in column 1 indicates the order of magnitude the variable is multiplied by to equal the number in the table. (For example, x 10 in column 1 means 3.44 x 10 was multiplied by 1 x 10 before tabulating it as 3.44 in column 2.)... 

Eq. (B.l) will allow fairly accurate estimates of the aetivity coefficients in mixtures of electrolytes if the ion interaction coefficients are known. Ion interaction coefficients for simple ions can be obtained from tabulated data of mean activity coefficients of strong electrolytes or from the corresponding osmotic coefficients. Ion interaction coefficients for complexes can either be estimated from the charge and size of the ion or determined experimentally from the variation of the equilibrium constant with the ionic strength. 

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