Standard free energy of dissociation

It seems reasonable then to conclude that the heat of formation of NF4+ is greater than 225 kcal./mole and probably less than 260 kcal./ mole a value around 240 kcal./mole seems not unlikely. This implies that dissociation of NF4+ to NF3+ and F should be endothermic by 50 25 kcal./mole, and dissociation to NF2+ + F2 endothermic by 38 24 kcal./ mole. The increase of standard entropy in the latter dissociation is estimated about 45 e.u. this will contribute —13.5 kcal./mole to the standard free energy of dissociation at 300°K. It is thus not unlikely that the ion NF4+ can be prepared and observed in the gas phase by a suitable ion-molecule reaction. 

The justification for equation 1 has been presented (3) where AG°3(H20) is the standard free energy of dissociation (homolytic) in aqueous solution and AH°3(gas) is the standard enthalpy of dissociation in the gas phase for an H-X molecule or H-B+ ion. 

The standard heats of formation AH of gaseous HX diminish rapidly with increase in molecular weight and HI is endothermic. The very small (and positive) value for the standard free energy of formation AGj of HI indicates that (under equilibrium conditions) this species is substantially dissociated at room temperature and pressure. However, dissociation is slow in the absence of a catalyst. The bond dissociation energies of HX show a similar trend from the very large value of 574kJmol for HF to little more than half this (295kJmol ) for HI. 

The electrochemical standard free enthalpy, of dissociation of the surface acid or base sites consists of the chemical standard free enthalpy, AG°, an electrostatic energy, eA, and an interaction energy, m0, for the adsorption coverage in the Frumkin adsorption model is the potential across the compact layer, 0 is the adsorption coverage, and m is the Frumkin parameter [Frumkin, 1925] ... 

From the values given in the table the equilibrium constants of the hydrogen halogenides can be calculated by use of the equation AF° = —RTlnK. The calculated values are somewhat uncertain because of uncertainty in the estimate of the standard free energy of solution of the dissociated molecules. The values obtained in this way are 2 X 10 for HC1, 5 X 10s for HBr, and 2 X 109 for HI. These acids are accordingly very strong acids. 

Here we have introduced a detailed formalism for building models of biochemical systems. This approach has the advantages that the influences of pH and metal ion concentrations on apparent thermodynamic properties are explicitly accounted for. This detailed accounting allows us to take advantage of the rich data available on dissociation constants and thermodynamic properties. Even so, the available data remain incomplete. While standard free energies of formation are... 

An entirely different method of arriving at this standard free energy change is based partly on e.m.f. measurements, and partly on equilibrium data. From the dissociation pressure of mercuric oxide at various temperatures it is possible to obtain the standard free energy of the reaction... 

A thermodynamic investigation of the solubility and extraction of tetraphenylarsonium pertechnetate, Ph4AsTc04, has been carried out in a large number of solvents. The standard free energies of transfer have been used to characterize the difference between the solubility in HjO and in organic solvents. The concentration dependence of the distribution coefficients is a function of the dissociation and association of Ph4AsTc04 in the two phases. 

From the standard free energies of formation of PbS04( ), Pb++ and SV)7 calculate the solubility product of lead sulfate at 25 C. Aibuming complete dissociation, estimate the solubility in water, in terms of molality. 

From the standard free energies of formation of OH ions and of UiO(I), calculate the dissociation product (X ) of water at 26° C. 

Lassiter studied the dissociative adsorption of SO2 on polycrystalline silver and postulated, by comparison of the standard free energies of formation, that Ag2S was likely to be formed. 

For the same reasons as for IF , IF should be approximately independent of ATha- Since AF, the standard free energy of a proton transfer from HA to an acceptor, must vary with A in exactly the same way as the free energy of acid dissociation, AF a, and since AF is the sum of IF , IF , and AF the latter must be given by AF a plus a constant. Thus the variation in a as a function of the acidity of HA should be given by (4). In the present paper, (4) is shown to... 

Figure II Relative free energy of dissociation of hydrogen chloride versus water along various isochores and isobars from the standard continuum model.

This value, calculated with the standard fre energies of formation compiled by the NBS, represents the dissociation constant of the bisulfate ion at 25 Celsius (298.15 Kelvins) which is the reference temperature for their compilation. The accepted value of this equilibrium constant as given in Robinson and Stokes (1) determined experimentally is. 0104 i. 0003. The experimental result agrees quite well with that calculated from the standard free energies of formation and the difference between the results represents a difference in a of... 

Solubility of calcium hydroxide Dissociation constant of water Solubility product of CaCOa Standard free energies of formation CO, (9)... 

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