Sodium free energy change

Since the sodium ion binding constant, K, for the first ion to enter the channel is 63 M 1, the free energy change on binding, AGJ, is... 

Equation (a) forms the basis removing Ca from sodium. The free-energy change for the reaction is highly favorable, and even at small concentrations of Ca in sodium the addition of oxygen should result in the formation of insoluble CaO. 

At equilibrium there is a zero free-energy change, AG=0, that takes place between compartments separated by a membrane, with the free-energy change being dependent on the difference in concentration of various ions and the electrical potential difference that exists across the membrane. The relationships among sodium, potassium, and chloride ions, pH, and electrolytic potential have become known as Donnan equilibria. The concentrations and electrolytic potentials are related by the following equation ... 

A predictive molecular thermodynamics approach is developed for microemulsions, to determine their structural and compositional characteristics [3.7]. The theory is built upon a molecular level model for the free energy change. For illustrative purposes, numerical calculations are performed for the system water, cyclohexane, sodium dodecyl sulfate as surfactant, pentanol as cosurfactant and NaCl as electrolyte. The droplet radius, the thickness of the surfactant layer at the interface, the number of molecules of various species in the droplets, and the distribution of the components between droplets and the continuous phase are calculated. The theory also predicts the transition from a mi-... 

Singh and coworkers examined the effect of polarization energy on computed relative solvation free energies of ions as well. The calculated solvation free energies with and without polarization and experimental values for the mutations of ammonium ion to tetramethyl ammonium ion, chloride ion to bromide ion and sodium ion to potassium ion were -23.56 kcal/mol, -29.82 kcal/mol, -31.70 kcal/mol, -1.95 kcal/mol, -3.23 kcal/mol, -3.33 kcal/mol, -24.66 kcal/mol, -20.09 kcal/mol, and -17.05 kcal/mol, respectively. Therefore, polarization energy added a constant positive value to the free energy change for all the transformations except for the mutation of sodium ion to potassium ion. 

The two best-studied ions are Na" and K". The preference of quadruplex central cavity for potassium over sodium ions is the result of two opposite effects from one side the free energy of Na" binding to a quadruplex is more favourable than that of K, but from the other side this effect is more than compensated by the much greater cost of Na dehydration. " The net result is a free energy change in favour of the potassium form. The number of released ions upon melting of the human telomeric quadruplex can be estimated by melting experiments as 5 in the presence of NaCl and 6 in the presence of KCl. Note that this value should not be interpreted as the number of ions bound in the quadruplex channel, as the total number of ions released on thermal denaturation includes the ions bound in the quadruplex channel, and the difference between the number of ions condensed on the quadruplex and on the random coil. In our hands, the dilfer-ences in thermal stability between the sodium and potassium forms of a quadruplex are very sequence dependent values (Tni(K+) — Ln(Na+)) are... 

An analysis of the reduction procedures just described shows two important facts that are common to both The sodium is in a state of maximum dispersion, a dispersion of atomic dimensions, and the chemical form of the sodium is different from the consolidated metal itself. If low temperature reaction with metal halides requires that the chemical form of sodium be altered, there can be little hope that sodium metal as such will show the same reactivity this implies that the free energy change for the reaction involving massive sodium is not favorable. This is not the situation, however thermochemical calculations (I) indicate a favorable free energy change of such magnitude that most metal halides should react spontaneously with sodium metal at room temperature. As this is not the case, one... 

The results may be compared with the observed sequences O ) for reactions involving equilibrium between the alkali metal cations and carboxylated polyanions, which give an order of affinity Li>Na>K. The equilibrium sequence, which is a measure of the free energy change in the reaction, can only be reconciled with the enthalpy data if the endothermic replacement of the condensed sodium ion by a lithium ion is accompanied by an increase in the total entropy. This would accord with the observed order of volume changes, Li>Na>K, for the site binding (condensation) of alkali metal cations to polycarboxylates,... 

Many other examples could be cited which show a smooth variation of k /kP with the strength of the base, and in a few cases some indication of a maximum isotope effect when ApK (and hence the standard free energy change of the reaction) is close to zero. Such a maximum may well be concealed in the results for sodium propan-2-one-l-sulphonate in Table 25, since kP/k has almost the same value for reaction with 2,6-lutidine and hydroxide, for which ApK is -h7.4 and —2.0 respectively. One way of changing the value of Api is to modify the nature of the solvent, and in particular the addition of dimethyl sulphoxide to aqueous solutions containing hydroxide ions will displace the equilibrium SH-hOH"... 

The excess free energy functions given by integration of the excess isotherms, Eq. (5), reflect the extent of the hydrophobization (Fig. 14). Methanol displaces benzene with a maximum change in free energy on sodium illite. The displacement process results in smaller free energy changes on HDP-treated surfaces— the functions shown for the sample with maxima at the azeotropic compositions. 

Calculate the free energy change for the decomposition of sodium chlorate. Assume reactants and products are at 25°C ... 

Draw a Gibbs free energy cycle to calculate the standard Gibbs free energy change of decomposition of sodium hydrogencarbonate. 

Consider an alchemical transformation of a particle in water, where the particle s charge is changed from 0 to i) (e.g., neon sodium q = ). Let the transformation be performed first with the particle in a spherical water droplet of radius R (formed of explicit water molecules), and let the droplet then be transferred into bulk continuum water. From dielectric continuum theory, the transfer free energy is just the Born free energy to transfer a spherical ion of charge q and radius R into a continuum with the dielectric constant e of water ... 

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