Solutions factors that affect solubility

Energy Changes and the Solution Process 200 Factors That Affect Solubility 203... 

There are two major divisions in a discussion of solutions solution formation and solubility equilibria. The first topic deals with the mechanisms by which solutions form—different ways to describe solutions, factors that affect solution formation, and some of the physical properties of solutions. Those are the domain of this chapter. Solubility equilibria are discussed in Chapter 15, after you ve had a chance to review the concept of equilibrium. 

In this section, you learned the meanings of several important terms, such as solvent, solute, saturated solution, unsaturated solution, aqueous solution, and solubility. You need to know these terms in order to understand the material in the rest of the chapter. In section 8.2, you will examine the factors that affect the rate at which a solute dissolves in a solvent. You will also learn about factors that affect solubility. 

You have taken a close look at the attractive forces between solute and solvent particles. Now that you understand why solutes dissolve, it is time to examine the three factors that affect solubility molecule size, temperature, and pressure. Notice that these three factors are similar to the factors that affect the rate of dissolving. Be careful not to confuse them. 

The final factor that affects solubility is pressure. Changes in pressure have hardly any effect on solid and liquid solutions. Such changes do affect the solubility of a gas in a liquid solvent, however. The solubility of the gas is directly proportional to the pressure of the gas above the liquid. For example, the solubility of oxygen in lake water depends on the air pressure above the lake. 

You have learned about the process of solvation and the factors that affect solubility. The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution. How would you describe the concentration of the solutions in Figure 15-11 Concentration may be described qualitatively using the words concentrated or dilute. In general, a concentrated solution, as shown on the left in Figure 15-11, contains a large amount of solute. Conversely, a dilute solution contains a small amount of solute. How do you know that the tea on the right in Figure 15-11 is a more dilute solution than the tea on the left ... 

Factors that affect solubility include the nature of the solute and solvent, temperature, and pressure. 

The solubilities of substances do not depend only on the amount of solute or solvent. Temperature and pressure are also factors that affect solubility. As for stirring, even if it seems to increase solubility, it actually has no effect. Stirring only speeds up dissolution. 

Aqueous solubility is one of the most important physicochemical properties. It is believed that a drug has to be in solution to be absorbed.35 From the pharmaceutical development point of view, the solid state form is another important factor that affects solubility, the dissolution rate, and eventually developability. The solid state form is the determinant of, to some extent, physicochemical stability, intellectual property, and formulation scalability this factor should be carefully examined and optimized. Change in crystallinerity from different chemical processes, in some cases, results in a big difference in bioavailability when the drug is delivered by a solid dosage formulation. 

In summarizing reversed-phase SPE, both the and the log of the octanol-water partition coefficient of the compound are related to the aqueous solubility of the analyte, although the relationship is not always straightforward because there are other factors that affect solubility of an analyte but that do not affect sorption, such as crystal lattice energy for solids. In spite of this factor, one could theoretically estimate the from the solubility of the analyte and relate this solubility to the capacity of the solute for the reversed-phase sorbent. The ability to use solubility to predict capacity is also addressed... 

FACTORS THAT AFFECT SOLUBILITY (SECTION 17.5) Several experimental factors, including temperature, affect the solubilities of ionic compounds in water. The solubility of a slightly soluble ionic compound is decreased by the presence of a second solute that furnishes a common ion (the common-ion effect). The solubility of compounds containing basic anions increases as the solution is made more acidic (as pH decreases). Salts with anions of negligible basicity (the anions of strong acids) are unaffected by pH changes. 

The factors that affect the energetics of solid solutions and indirectly solid solubility are to a large extent the same as those that control the enthalpy of formation of compounds. Most often the differences between the atomic radii of the participating elements, in electronegativity and in valence electron density are considered for solutions of elements. For solid solutions of binary compounds, similar factors are used, but some measure of the volume of the compounds is often used instead of atomic radii. 

It is important to make the distinction between solubility and the solubility product constant. Solubility refers to the amount of a substance that can dissolve to form a saturated solution. The solubility of a substance is usually expressed in grams solute per liter of solution (g/L). Sometimes, however, it is described in moles solute per liter of solution, in which case it is referred to as the molar solubility of the substance. At any given temperature, the solubility-product constant, Ksp, for a solute remains constant. The solubility of a solute is not necessarily constant because it is affected by the concentrations of other dissolved substances. In the next section we will look at some factors that affect the solubility of a solute. 

As you learned in section 8.1, the solubility of a solute is the amount of solute that dissolves in a given volume of solvent at a certain temperature. Solubility is determined by the intermolecular attractions between solvent and solute particles. You will learn more about solubility and the factors that affect it later in this section. First, however, you will look at an important property of a solution the rate of dissolving, or how quickly a solute dissolves in a solvent. 

In Chapter 8, you examined factors that affect the solubility of a compound. As well, you learned that the terms soluble and insoluble are relative, because no substance is completely insoluble in water. Soluble generally means that more than about 1 g of solute will dissolve in 100 mL of water at room temperature. Insoluble means that the solubility is less than 0.1 g per 100 mL. While many ionic compounds are soluble in water, many others are not. Cooks, chemists, farmers, pharmacists, and gardeners need to know which compounds are soluble and which are insoluble. (See Figure 9.1.)... 

The solubility of an organic compound in water is one of the key factors that affects its environmental behavior (.1—3). The aqueous solubility is a fundamental parameter in assessing the extent of dissolution of environmentally important substances and their persistence in an aquatic environment. The extent to which aquatic biota is exposed to a toxicant is largely controlled by the aqueous solubility. In addition, these solubilities are of thermodynamic interest in elucidating the nature of these highly nonideal solutions (1,2). 

In practice, the choice of substrate concentrations is limited by such considerations as the solubility of the substrates, the viscosity and high initial absorbance of concentrated solutions, and the relative costs of the reagents. Furthermore, the selection of appropriate substrate concentrations is only one of the factors to be considered in formulating an optimal assay system for the measurement of a specific enzyme activity. Critical choices must also be made with respect to other, frequently interdependent factors that affect reaction rate, such as the concentrations of activators and the nature and pH of the buffer system. The traditional empirical approach to optimization has been replaced by newer techniques of simplex co-optimization and response-... 

Solubility is affected by many factors. One of the most important factors is pH. Other factors that affect the solubility of the drug include temperature, hydrophobicity of the drug, solid form of the drug, and the presence of complexing agents in solution. 

Soil pH measurements can be ambiguous. Two factors that affect soil pH measurements are the soil-solution ratio and the salt concentration. Increasing either factor normally decreases the measured soil pH because H and A1 cations on or near soil colloid surfaces can be displaced by exchange with soluble cations. Once displaced into solution, the A1 ions can hydrolyze (Eq. 10.2) and further lower the pH. Preferential retention of hydroxy aluminium polymers by soil colloids drives the hydrolysis reactions further toward completion and leads to lower pH. Increasing the neutral salt concentration to 0.1 or 1 M can lower the measured soil pH as much as 0.5 to 1.5 units, compared to soil pH measured in distilled water suspensions. 

Solubility is affected by temperature and by the presence of other solutes. The presence of an acid, for example, can have a major influence on the solubility of a substance. In Section 17.4 we considered the dissolving of ionic compounds in pure water. In this section we examine three factors that affect the solubility of ionic compounds (1) presence of common ions, (2) solution pH, and (3) presence of complexing agents. We will also examine the phenomenon of amphoterisniy which is related to the effects of both pH and complexing agents. 

The nature of the chemical is an important factor that affects vapour density. Chemical s properties such as vapour pressure, solubility in water, etc. are important properties of a chemical that influence its vapour density. The chemical s absorption capacity also affects vapour density and the volatilization rate. Absorption of the chemical by the organic and inorganic soil components may be the result of chemical absorption (Coulombic forces), physical absorption (van der Waals forces) and hydrogen bonding [30]. Absorption reduces the chemical activity below that of the pure compound and affects the vapour density and subsequently the volatilization rate [10]. This is because the concentration of the compound present in a desorbed state in solution in the soil water controls the vapour density of the compound in soil air. 

Among the factors that affect column efficiency and selectivity are the structure of the mesogen (in relation to the solutes of interest), the phase type(s) and degree of ordering, temperature, column loading and coverage, concentration (solubility) effects, and the surface structure and specialized treatment of the support. The column surface can dramatically affect the orientation of the liquid crystalline molecules (especially for monomeric mesogens) and thus alter separation efficiency. For polymeric liquid... 

One factor which affects the extent of polymer-solvent interactions is relative molar mass of the solute. Therefore the point at which a molecule just ceases to be soluble varies with relative molar mass, which means that careful variation of the quality of the solvent can be used to fractionate a polymer into... 

---