More Solutions

Like dissolves like polar solvents dissolve polar solutes nonpolar solvents dissolve nonpolai solutes. 

Ionic compounds are dissolved by polar substances. When ionic compounds dissolve, they break apart into their respective cations and anions and are surrounded by the oppositely charged ends of the polar solvent. This process is called solvation. Water acts as a good solvent for ionic substances. The water molecules surround the individual ions pointing their positive hydrogens at the anions and their negative oxygens toward the 

For the MCAT you should be aware of common names, formulae, and charges for the polyatomic ions listed on the right. 

When ions form in aqueous solution, the solution is able to conduct electricity. A compound which forms ions in aqueous solution is called an electrolyte. Strong electrolytes create solutions which conduct electricity well and contain many ions. Weak electrolytes are compounds which form few ions in solution. 

There are several ways to measure the concentration of a solution, five of which you should know for the MCAT molarity (M), molality ), mole fraction (%), mass percentage and parts per million (ppm). Molarity is the moles of the compound divided by the volume of the solution. Molarity generally has units of mol/L. Molality is moles of solute divided by kilograms of solvent. Molality generally has units of mol/kg and is usually used in formulae for colligative properties. The mole fraction is the moles of a compound divided by the total moles of all species in solution. Since it is a ratio, mole fraction has no units. Mass percentage is 100 times the ratio of the mass of the solute to the total mass of the solution. Parts per million is 106 times the ratio of the mass of the solute to the total mass of the solution. 

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The energetics and kinetics of film formation appear to be especially important when two or more solutes are present, since now the matter of monolayer penetration or complex formation enters the picture (see Section IV-7). Schul-man and co-workers [77, 78], in particular, noted that especially stable emulsions result when the adsorbed film of surfactant material forms strong penetration complexes with a species present in the oil phase. The stabilizing effect of such mixed films may lie in their slow desorption or elevated viscosity. The dynamic effects of surfactant transport have been investigated by Shah and coworkers [22] who show the correlation between micellar lifetime and droplet size. More stable micelles are unable to rapidly transport surfactant from the bulk to the surface, and hence they support emulsions containing larger droplets. 

The problem presented to the designer of a gas-absorption unit usually specifies the following quantities (1) gas flow rate (2) gas composition, at least with respect to the component or components to be sorbed (3) operating pressure and allowable pressure drop across the absorber (4) minimum degree of recoverv of one or more solutes and, possibly, (5) the solvent to be employed. Items 3, 4, and 5 may be subject to economic considerations and therefore are sometimes left up to the designer. For determining the number of variables that must be specified in order to fix a unique solution for the design of an absorber one can use the same phase-rule approach described in Sec. 13 for distillation systems. 

Adsorption and ion exchange share so many common features in regard to apphcation in batch and fixed-bed processes that they can be grouped together as sorption for a unified treatment. These processes involve the transfer and resulting equilibrium distribution of one or more solutes between a fluid phase and particles. The partitioning of a single solute between fluid and sorbed phases or the selectivity of a sorbent towards multiple solutes makes it possible to separate solutes from a bulk fluid phase or from one another. 

For mixtures of substances, it is convenient to express compositions in ntole fractions or mass fractions. A process stream seldom consists of a single component. It may also contain two or more phases, or a mixture of one or more solutes in a liquid solvent. The following definitions are often used to represent the composition of component A in a mixture of components. 

Liquid-liquid extraction is a technique in which a solution (usually aqueous) is brought into contact with a second solvent (usually organic), essentially immiscible with the first, in order to bring about a transfer of one or more solutes into the second solvent. The separations that can be performed are simple, clean, rapid, and convenient. In many cases separation may be effected by shaking in a separatory funnel for a few minutes. The technique is equally applicable to trace level and large amounts of materials. 

Table 16-2 also provides a list of 15 equations that can be solved simultaneously to yield the equilibrium condition (Taylor et ah, 1983). Furthermore, if the concentration of each species is calculated as a function of pH (the so-called master-variable diagram or Sillen diagram, named after Sillen (1967) who popularized the method, it is possible to examine various sensitivities in the system, e.g., to the addition of more solute (see explanatory box on Sillen diagrams). 

Any solution contains at least two chemical species, the solvent and one or more solutes. The mass of a solution is the sum of the masses of the solvent and all dissolved solutes. To answer questions such as How much is there about solutions, we need to know the amount of each solute present in a specified volume of solution. The amount of a solute in a solution is given by the concentration, which is the ratio of the amount of solute to the amount of solution. In chemistry the most common measure of concentration is molarity (M). Molarity is the number of moles of solute (n) divided by the total volume of the solution (V) in liters ... 

A solution is a homogeneous mixture of two or more substances. As described in Chapter 3, a solution contains a solvent and one or more solutes. The solvent determines the state of the solution, and normally the solvent is the component present in the greatest quantity. The most common solutions are liquids with water as solvent, but solutions exist in all three states of matter. The atmosphere of our planet, air, is a gaseous solution with molecular nitrogen as the solvent. Steel is a solid solution containing solutes such as chromium and carbon that add strength to the solvent, iron. 

In crystallization from solution, as in the manufacture of salt from brine, the liquid phase is multicomponent, having one or more solvents and one or more solutes. Here both temperature and concentration are determining factors. 

Solvents, however, are only able to dissolve (solvate) a limited amount of solute. As solute is added to a solvent and the solution is being formed, the solvent has an ever-decreasing ability to dissolve more solute. As long as the solvent is able to dissolve more solute, the solution is unsaturated. When the solvent can no longer dissolve additional solute, the solution is saturated. Any additional solute added will collect on the bottom of the container and remain undissolved. The amount of solute that can be dissolved in a given amount of solvent at a specific temperature and pressure is defined as the solubility of the solute. 

Describe each of the solutions indicated as saturated, unsaturated, supersaturated, or impossible to tell, (a) More solute is added to a solution of that solute, and the additional solute all dissolves. Describe the original solution. (6) More solute is added to a solution of that solute, and the additional solute does not all dissolve. Describe the final solution, (c) A solution is left standing, and some of the solvent evaporates. After a time, some solute crystallizes out. Describe the final solution, (d) A hot saturated solution is cooled slowly, and no solid crystallizes out. Describe the cold solution, (e) A hot solution is cooled slowly, and after a time some solid crystallizes out. Describe the cold solution. (/) A hot saturated solution is cooled slowly, and no solid crystallizes out. The solute is a solid that is more soluble hot than cold. Describe the cold solution. 

Arts, (a) The original solution was unsaturated, since it was possible to dissolve more solute at that temperature. (b) The final solution is saturated it is holding all the solute that it can hold stably at that temperature, so not all the excess solute dissolves, (c) The final solution is saturated it has solid solute in contact with the solution, and that solute does not dissolve. The solution must be holding as much as it can at this temperature. (d) It is impossible to tell with just this information [sec part (/)]. The solute may get more soluble as the solution cools, (e) The solution is saturated. (/) The solution is supersaturated it is holding more solute than is stable at the colder temperature. 

When the saturation limit is exceeded and excess pure solid remains undissolved and in contact with the solvent, the number of phases present now equals two. However, there are still only two components in the system, leading to the deduction that the number of degrees of freedom is zero. In practical terms, this means that there can be no variation in concentration as more solute is added to the system, and segment B-C of Fig. 5 is obtained. When solubility diagrams are obtained that exactly match the type shown in Fig. 5, it can safely be assumed that the solute under analysis is at least 99.9% pure. 

The propulsion system, which establishes and controls accurately the flow of one or more solutions containing the reagents needed for initiating the CL reaction or, in some cases, merely acting as carrier for the sample that will be introduced later in this stream. 

In the development of physical chemistry, investigations of dilute solutions have been very important. A dilute solution consists of the main constituent, the solvent, and one or more solutes, which are the diluted species. As early as in 1803 William Henry showed empirically that the vapour pressure of a solute i is proportional to the concentration of solute i ... 

Test Ttibe 5 0.1 M A1(N03)3 When I mixed samples of test tube 5 with a sample from test tube 3, a white precipitate formed. No heat was evident. The white precipitate could have been either Al(OH)3 or Sn(OH)4, however, since no heat was produced and the A1(N03)3 did not contain an acid, it can be concluded that test tube 5 contained A1(N03)3. When I mixed samples of test tube 5 which I believed contained Al3+ with samples of test tube 2 which I believed contained OH, a white precipitate formed which I believed to be Al(OH)3. When I added more solution from test tube 2, increasing the OH" concentration, the precipitate dissolved, consistent with a shift in equilibrium. 

Symporters are membrane-spanning proteins which translocate two or more solutes in the same direction across the cell membrane. In epithelial tissue, such... 

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