Dissociable solutes

For example, in the case of dilute solutions, the van t Hoff s equation may be used to piedict the osmotic pressure (jr = CRT) where n is the osmotic pressure of the solution, C is the molar concentration of the solute, ft is the universal gas constant and T is the absolute temperature, Fm dissociating solutes, the concentration is that of the total ions. For example, NaCI dissociates in water into two ions Na" " and Cl . Therefore, the total molar concentration of ions is hvice the molar concentration of NaCI. A useful rule of thumb for predicting osmotic pressure of aqueous solutions is 0,01 psi/ppm of solute (Weber, 1972). 

Suppose now that we build a series of cells, alike in all respects save that the (very dilute and completely dissociated) solute has a different concentration in each cell. If the cells are alike in all other respects, the unitary terms must be the same in each coll the values of the e.m.f. for the various cells will differ owing to the difference in the communal terms. In very dilute solutions the contribution made to each communal term by the interionic forces will be small, and the dependence of the e.m.f. on the concentration will arise almost entirely from the cratic term which, for each solute species, may be written — kT In y or — IcT In x. Since we are considering a uni-univalent solute, the numerical values of y+ and t/ for the positive and negative ions will both be the same as the mole ratio of the solute. 

The acidic character of acids depends on the availability ofhydrogen ions in their solution. An acid X3 is said to be stronger than another acid X2 if, in equimolar solutions, X3 provides more hydrogen ions than does X2. This will be possible provided that the degree of dissociation of X3 is greater than that of X2. Based on the Arrhenius theory of electrolytic dissociation, solutions may be classified in the manner shown in Figure 6.1. If the ionization of an acid is almost complete in water, the acid is said to be a strong acid, but if the... 

The ideal solubility of a non-dissociating solute, assuming the effects of pressure and specific heat capacity change on melting are negligible is [7,8] ... 

Fig. 5.15 Analytical set-up for on-line label-free assay based on ESI-MS. MS instrument Ion-trap mass spectrometer (LCQ Deca, Thermo Electron). PI Carrier/HPLC pump. P2 HPLC pump delivering receptor solution. P3 HPLC pump delivering dissociation solution. PA HPLC pump for final LC-MS analysis of released ligands. 1 Mixing union. 2 Microcoil reactor. VI injection valve.

If you have a class with biochemists, clearly the area of enzyme kinetics is practically mandatory. If biologists are mixed in with the biochemists, osmotic pressure is an important concept to cover carefully and a concept typically not well covered in general chemistry and in most physical chemistry texts or classes. A quick example what is a 2 Osmolar solution of sodium chloride Such concentration units are used when dispensing various saline solutions in hospitals. What is the origin of the unit A 1 M NaCl solution dissociates into two ions that would double the osmotic pressure of a non dissociating solute. Thus, the 1 M solution of NaCl becomes a 2 Osmolar solution. Other examples abound - the bursting pressure of a cell relates to the osmotic pressure of the serum in which the cell finds itself. 

Neonatal rats (1-2 days old) are killed by decapitation and then sprayed with 70% ethanol for desinfection. After thoracotomy the pericard is opened and the heart removed. Bath the organ in ice-cold PBS/glucose solution in a Petri dish to remove blood. Remove atria, transfer the heart to another Petri dish, chop up the ventricles with two sterile scalpels and incubate in 7 ml desaggregation solution and stir gently (140 rpm) at 37 °C. Allow sedimentation of the tissue and remove the supernatant. Add fresh dissociation solution and repeat this procedure 6 times. Suspend the supernatants in the medium for resuspension of supernatants (each in 8-9 ml, ice-cold). 

The addition of dissociable solutes to water disrupts its normal tetrahedral structure. Many simple inorganic solutes do not possess hydrogen bond donors or acceptors and therefore can interact with water only by dipole interactions (e.g. Figure 7.5 for NaCl). Multilayer water exists in a structurally disrupted state while bulk-phase water has properties similar to... 

On the basis of dissociative solution, i.e., hydrogen is absorbed as H atoms rather than H2 molecules, the relative partial molar free energy of absorption is related to the equilibrium constant via the equilibrium hydrogen pressure (Equation 3). Values of the relative partial molar enthalpy as a function of hy-... 

That is, basic and neutral amino acids follow the pattern long recognized for strongly dissociated solutions which promote transformation, whereas acidic amino acids form a protective overgrowth on the aragonite surface via carboxyl groups. 

We will see in Chapter 10, when we deal with the dissociation of electrolytes into ions, that, in general, the chemical potential of a dissociating solute is the chemical potential of its component parts, whereas the activity of the solute is the product of the component parts. 

The value of the fraction representing the ratio of the conductances of two differently concentrated but fully dissociated solutions can be calculated from Onsager s equation (see III-14) which enables us to determine the effect of electrostatic forces of attraction in strong, i. e. fully dissociated electrolytes. In the case of weak electrolytes, however, it is necessary to substitute ct in Onsager s equation by the real concentration of ions, i. e. by equivalent conductance of a hypothetical, fully dissociated solution is considered. In this way we obtain the following equation ... 

For an ideal solution, Jq = I and is unity. Then Eq. (9) is consistent with Eq. (10 11), since the total molality of all solute species is vm for a completely dissociated solute of molality m. For ionic solutions, the Debye-Hiickel theory predicts a value of yo different from unity and therefore a deviation of g from unity. A treatment of this aspect of the Debye-Hiickel theory is beyond the scope of this book, and we shall merely state the result. The osmotic coefficient g at 0°C for dilute solutions of a single strong electrolyte in water is given by... 

For very dilute solutions c fo (region I of Figure 4.1), the equilibrium is described by Seivert s law which is simply Henry s law for a dissociating solute [46]. 

The standard transformed enthalpies of formation of the three species are given by the following six equations. dHlzero, dH2zero, and dH3zero are also related by the equations for the enthalpy of dissociation. ) solution s Solve [ (dHlexpt == dHlzero +1.4775 (zi[[l]] 2 - nHi[ [1] ]) ionstr 0.5 / (1 + 1.6 ionstr 0.5), dH2expt == dH2zero +... 

A similar expression can be obtained for the symmetric and the unsymmetric mole fraction activity coefficient. In a completely dissociated solution of n mol Na2S04, the mean molal activity coefficient is... 

The simplest system of electrolyte solution is one solvent, say water (W) and one, completely dissociable solute, say KC1, which we denote by S. It is assumed that S dissociates completely into two fragments... 

In this section, we generalize this relation to solutes which dissociate in the liquid. The most important solutes of this kind are electrolytes, but the treatment is general and applies to any type of dissociable solutes. 

Figure 7.10 An analogous five-step process to transfer a dissociated solute from the gaseous phase to the liquid phase. Here the various "conformers" are the various "dimers" defined by distance Rab (instead of the angle 4> in figure 7.8). The analog of the species 1 in figure 7.8 is here the "species" at RAB = oo.

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