Solubility, of solids

We have already calculated the ideal solubility for a solid that follows Raoult s Law in solution and for which we can write 

Applying the Gibbs-Helmholtz equation (Section 4.4) as before we obtain 

This equation has the same form as that obtained for ideal solubility but AHfvs has been replaced by the enthalpy of solution AHmjx. In non-ideal solutions of solids in liquids which do not follow either Henry s or Raoult s Laws, AHmix is the differential enthalpy of solution of the solute in the saturated solution. Both AGmix and AHmix are for non-ideal solutions similar to the reaction free energy we introduced when studying equilibrium in chemical reactions. They are all differential quantities AHmix is the enthalpy change when one mole of solute is added to an infinite volume of nearly 

At a given temperature the vapour pressures of two liquids which are completely miscible and form an ideal solution are 0.2 atm and 0.5 atm respectively. Estimate the mole fractions in both vapour and liquid phases at equilibrium when the total vapour pressure of the solution is 0.35 atm. 

The vapour pressure of ether, (C2Hs)20, is 445mmHg at 293 K. That of a solution of 12.2 x 10 3 kg benzoic acid, C6H3C02H in 0.100 kg ether is 413 mmHg. Calculate the molecular weight of the benzoic acid in ether. 

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A series of studies has been made by Yalkowsky and co-workers. The so-called general solubility equation was used for estimating the solubility of solid nonelectrolytes [17, 18]. The solubility log S (logarithm of solubility expressed as mol/L) was formulated with log P logarithm of octanol/water partition coefficient), and the melting point (MP) as shown in Eq. (11). This equation generally... 

When interpreting proton transfers in Chapter 7, we found that the experimental data showed that for most solute species in aqueous solution the values of J lay between 0.25 and 1.0 electron-volts. We shall now be interested in the values of L that are necessary to account for the observed solubilities of solids in water. We may expect the range of values of L to be rather similar the main difference is that in the solution of a crystal the value of Aq in (8G) is never less than 2, whereas in most of the proton transfers discussed in Chapter 7 the value of Aq was either unity or zero. 

The principles of equilibrium have wide applicability and great utility. For example, they aid us in understanding and controlling the solubility of solids and gases in liquids. We shall consider, first, the solubility of a molecular solid in a liq-... 

Fig. 10-3. Maximum randomness versus minimum energy—solubility of solids and gases.

An application of Eq. (11) is shown in Fig. 2, which gives the solubility of solid carbon dioxide in compressed air at a low temperature. The solubility is calculated from the equation of equilibrium... 

An application of Eq. (19) is shown in Fig. 4, which gives the solubility of solid naphthalene in compressed ethylene at three temperatures slightly above the critical temperature of ethylene. The curves were calculated from the equilibrium relation given in Eq. (12). Also shown are the experimental solubility data of Diepen and Scheffer (D4, D5) and calculated results based on the ideal-gas assumption (ordinate scale is logarithmic and it is evident that very large errors are incurred when corrections for gas-phase nonideality are neglected. 

E6.7 Bronsted measured the solubility of solid orthorhombic and monoclinic sulfur at 298.15 K in various solvents (benzene, diethyl ether and ethanol). He found that the solubility of monoclinic sulfur is always 1.28 times that of orthorhombic sulfur. That is, the concentration of sulfur in the solution in equilibrium with monoclinic sulfur is always 1.28 times the concentration of sulfur in the solution in equilibrium with orthorhombic sulfur. Sulfur exists in these solvents exclusively in the form of Sg molecules. 

Nearly every substance that dissolves in water has an upper limit to its solubility. Solids, liquids, and gases all display this characteristic. The room-temperature solubility of solid NaCl in water is about 6 M. Liquid n-hexanol forms a saturated aqueous solution at a concentration of 5.6 X 10 M. Gaseous O2 in the Earth s atmosphere... 

SOLUBILITY OF SOLID PHASES AND THEIR MINERALOGICAL CHARACTERISTICS CONTROLLING DISTRIBUTION OF TRACE ELEMENTS AMONG SOLID PHASE COMPONENTS IN ARID SOILS... 

The solubility of solids in liquids is an important process for the analyst, who frequently uses dissolution as a primary step in an analysis or uses precipitation as a separation procedure. The dissolution of a solid in a liquid is favoured by the entropy change as explained by the principle of maximum disorder discussed earlier. However it is necessary to supply energy in order to break up the lattice and for ionic solids this may be several hundred kilojoules per mole. Even so many of these compounds are soluble in water. After break up of the lattice the solute species are dispersed within the solvent, requiring further energy and producing some weakening of the solvent-solvent interactions. 

Solubility of Solid Phases and Binding to Colloids and Particles... 

Allnatt). Solubility of Solids in Compressed Gases (Rowlinson and 11 1... 

In this chapter, you learned about solutions. A solution is a homogeneous mixture composed of a solvent and one or more solutes. Solutions may be unsaturated, saturated, or supersaturated. Solution concentration units include percentage, molarity, molality, and mole fraction. The solubility of solids in liquids normally increases with increasing temperature, but the reverse is true of gases dissolving in liquids. The solubility of gases in liquids increases with increasing pressure. 

Some substances will dissolve in a particular solvent and others will not. There is a general rule in chemistry that states that like dissolves like. This general statement may serve as an answer in the multiple-choice questions, but does not serve as an explanation in the free-response questions. This simply means that polar substances (salts, alcohols, etc.) will dissolve in polar solvents such as water, and nonpolar solutes, such as iodine, will dissolve in nonpolar solvents such as carbon tetrachloride. The solubility of a particular solute is normally expressed in terms of grams solute per 100 ml. of solvent (g/mL) at a specified temperature. The temperature must be specified because the solubility of a particular substance will vary with the temperature Normally, the solubility of solids dissolving in liquids increases with increasing temperature, while the reverse is true for gases dissolving in liquids. 

Very few generalized computer-based techniques for calculating chemical equilibria in electrolyte systems have been reported. Crerar (47) describes a method for calculating multicomponent equilibria based on equilibrium constants and activity coefficients estimated from the Debye Huckel equation. It is not clear, however, if this technique has beep applied in general to the solubility of minerals and solids. A second generalized approach has been developed by OIL Systems, Inc. (48). It also operates on specified equilibrium constants and incorporates activity coefficient corrections for ions, non-electrolytes and water. This technique has been applied to a variety of electrolyte equilibrium problems including vapor-liquid equilibria and solubility of solids. 

Chiou, C.T. and Manes, M. Application of the Flory-Huggins theory to the solubility of solids in glyceryl trioleate, / Chem. Soa, Faraday Trans. 1, 82(l) 243-246, 1986. 

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