Solubility of solids in liquids

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. 

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. 

In any discussion of solubility, it is important to remember solubility is temperature dependent. Generally, the solubility of solids in liquids increases with temperature. The variation of solubility in water varies greatly for different solutes. Figure 11.2 demonstrates that the solubility may increase... 

Solubility of solids in liquids V I is usually given in units of grams of solute per 100 mL of solvent. Because solubility changes with temperature, the temperature is also specified (usually 20°C room temperature). 

The solubility of solids in liquids often decreases as the pressure is raised, the reagents often crystallizing out from the solvents. The viscosity of liquids increases by approximately two times every 100 MPa, thus diffusion control of the reaction is important. 

The solubility of solids in liquids is typically attributed to the dielectric of the solvent, however this does not explain the situation here as is seen in Table 2. The low dielectric constant of the THF/MeOH system should make it a poor solvent for polyamic acid. Consequently, there must be other factors contributing to PAA solubility however, the causes of this solubility behavior have not been elucidated at this time. 

For the ideal solubilities of gases in liquids, a similar approach to that taken in Section 3.1 for the ideal solubilities of solids in liquids can be used and thus, Equation (3.69), analogous to Equation (3.8), is obtained ... 

The phase rule plays an important part in chemistry. For example, it helps to answer the controversial question of long standing whether the solubility of solids in liquids depends only on temperature, or also on pressure. Inasmuch as such a system is composed of two phases (liquid solution and a solid) and two components (solvent and solute), then... 

Similarly, in considering the solubility of solids in liquids, the only place where dissolution can occur is at the surface of the solid particles. The solid must be broken into smaller particles and then into molecules or ions, which can form a solution with the solvent molecules. 

Another most important issue is solubility. To date, no reliable methods are available to calculate and forecast the solubility of solids in liquids. 

Most rate processes Increase with Increasing temperature, for example, the solubilities of solids In liquids. Of course, there are exceptions, e.g., the solubility of water In polylmides ( ) and with plastics and elastomers there are upper temperature... 

In benzene the observed solubility of naphthalene at 298 K corresponds to a mole fraction of 0.29. However, the saturated solubility of this solute in hexane is given by x = 0.12 and in methanol by x = 0.025. The ideal solubility relation must be used with caution when attempting to estimate the actual solubility of solids in liquids. 

The study of vapor-liquid equilibria (Sec 10.1) of the solubility of gases in liquids (Sec. 11.1), and of the solubility of solids in liquids (Sec. 12.1), all involve nonsimple, mixtures. To see why this occurs, consider the criterion for vapor-liquid equilibrium ... 

Temperature affects the solubility of most substances, as shown by the data in Table 14.2. Most solutes have a limited solubility in a specific solvent at a fixed temperature. For most solids dissolved in a liquid, an increase in temperature results in increased solubility (see Figure 14.4). However, no single rule governs the solubility of solids in liquids with change in temperature. Some solids increase in solubility only slightly... 

The solubility of solids in liquid generally increases with increasing temperature and the solubility of most gases decreases with increasing temperature. Most reactions have their rates duplicated or triplicated with increasing temperature of 10 °C [3]. Gases such as O2, N2 and CO2 dissolve readily in water. 

Static capsules or pots of specieJ design are used to measure the solubility of solids in liquids. Eichelberger et al. [SO] used bimetallic capsules made by welding two crucibles. 

Equation (8 63), which was first put forward by Schroeder in 1893, may be used to estimate the ideal solubility of solids in liquids, from a knowledge of their melting-points and latent heats. It will be noted that the equation is entirely analogous to (8 48) which gives the depression of the freezing-point of the solvent a more accurate form of (8 63) could have been obtained by allowing for the temperature dependence of , as in 8 9. 

For solubility of solids in liquid, Hildebrand and Scatchard independentiy derived another equation, now called the Hildebrand-Scatchard equation ... 

The effect of temperature on the solubility of solids in liquids is more difficult to predict. Often, increasing the temperature increases the solubility of solids. However, an equivalent temperature increase can result in a large increase in solubility for some solvents and only a slight change for others. 

---