Ionic dissociation

Vdl W (64XT P7V d) exp( — f) where y is a factor of order unity for highly dissociated ionic surfactants (4). In practice, the interaction strength may... 

Like N2O4 (p. 457) it dissociates ionically in strong anhydrous acids such as HNO3, H3PO4, H2SO4, HSO3F and HCIO4, and this affords a convenient source of nitronium ions and hence a route to nitronium salts, e.g. ... 

A final point to bear in mind is that, when a reaction involves fully dissociated ionic compounds in solution, then the equilibrium constant should be written for the net ionic equation, by using the activity for each type of ion. 

In view of the observations of the ionic dissociation of nitro-cyano compounds, it is hardly surprising that even a hydrocarbon could dissociate ionically into a stable carbocation and carbanion, provided that the medium is polar enough to prevent the recombination reaction and to ensure equilibration. 

Another very interesting class of crosslinked polyelectrolytes are the so-called superabsorbents. They predominantly consist of crosslinked and (partially) neutralized poly(acrylic acid) and, hence, represent a network of flexible polymer chains that carry dissociated, ionic groups. Due to this structure they can function as water-swellable gels. Although they are hard, sandy powders in a dry... 

This suggests that we can also write the left-hand side of the reaction (3.126) in completely dissociated ionic form, analogous to (3.125) ... 

But no more than two of these five species are actually under independent control of the experimenter, because the dissociated ionic species concentrations are fixed by equilibrium conditions and are therefore not independent variables from the viewpoint of the experimenter. For example, if H20 and H2S04 are chosen as the two independently variable components, then the concentrations [H+], [HS04 ], [S04 ] of the remaining species could be determined by one ionic balance condition... 

The corrosion rate increases nearly up to the critical point, going downwards at higher temperatures. The reason is that water s dielectric constant decreases to around 2, so that dissociated ionic species decrease, the H+ concentration being very low. So electrochemical corrosion will be important in the zone about 300-390 °C, that is in heat exchangers but not in the reactor [17]. 

Hydrothermal systems such as these can also support the dissolution of ionic salts. There is a tendency for the organic components in these systems to be salted out of solution however conditions exist where a homogeneous system would contain both the dissociated ionic component and an aromatic component such as benzene (2). 

In anhydrous adds N204 dissociates ionically and in anhydrous HN03 dissoda-tion is almost complete ... 

As the Gibbs equation remains our primary tool, let us start with item (v). Some time ago this issue has given rise to a lively discussion in the literature but the issue is now resolved. Originally the question was whether for a fully dissociated ionic surfactant such as A Na or C Br" the adsorption term in the Gibbs equation (T dju ) should be written as RTF d In c or 2RTF d In c if the solution is ideal. We shall now analyze the problem thermodynamically. 

The aforesaid complexities make it virtually impossible to write explicit general equations for the rate of polymerization, kinetic chain length, average degree of polymerization as has been done above for a completely dissociated ionic initiator. With the exception of those simple cases discussed above, each system in anionic polymerization represents a kinetically unique problem and must be solved separately. 

Molality of HsSO Measured potential volts Degree of dissociation, Ionic strength So"... 

In anhydrous acids, N204 dissociates ionically, as in H2S04 above, and in anhydrous HN03 almost completely. 

The observation 185) on tantalum ribbons that, under controlled conditions, quantities of CO up to 300 monolayers can be taken up by the metal and then desorbed as molecular CO, indicates clearly that on this system at least, the CO molecule is able to be incorporated into the bulk. The suggestion 66) that on tungsten, only the substate contributes to the electron dissociative ionic cross-section of the phase, also does nothing to contradict the possibility of adsorbed CO molecules within the 2 a-nd jSg substates being closely associated with the electron well of the bulk metal. If this is the case, any ions produced by electronic interactions would be unable to leave the surface before neutralization by the electrons of the metal. 

However, there are additional complications in extending such calculations to the covalent (CH3)3CC1 molecule, involving the necessity of considering both the covalent bound and the dissociative ionic potential energy curves. 

Yet another aspect of this general question of the factors determining phase equilibria is illustrated by the partition of a solute between two solvents. In so far as the activity of a solute in a dilute solution is proportional to its concentration, the equilibrium distribution will be such that the ratio of concentrations in two immiscible solvents in contact is constant at constant temperature and pressure. The same principle will apply to the solution of a gas in a liquid. The concentration of dissolved gas is proportional to its partial pressure above the solution. These statements presuppose that the molecular complexity of the solute is the same in both phases, and that association or dissociation, ionic or otherwise, is excluded. 

Another kind of difficulty arises with pH-sensitive systems containing both an aqueous phase and an oil phase. It is due to the fact that the dissociated (ionic) and undissociated (nonionic) species are likely to selectively partition or fractionate between water and oil. As shown in Fig. 15, it can generally be assumed that the amount of dissociated salt in oil [Ac ] is negligible, whereas the amount of undissociated acid in water [AcH ,] is to be taken into account since it appears in the dissociation equilibrium [84,85]. 

Degree of ionization (a) Fraction of dissociated ionic headgroups at the micelle surface. A value of 1.0... 

The addition of low-molecular salts to a polyelectrolyte solution compensates the effects of the osmotic pressure as well as the coulomb forces by shielding the dissociated ionic groups as shown in Fig. 5.16. The addition of these salts allows for an extrapolation of the reduced viscosity to c O and a determination of an intrinsic viscosity. This is not possible for the salt free polyelectrolyte solution as can clearly be seen in Fig. 5.16. Although the addition of salt enables the determination of intrinsic viscosities, these values do not reflect the coil expansion in the salt free solution. 

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