The Characteristics of a Solution

A solution is a homogeneous mixture. This implies uniform distribution of solution components, so that a sample taken from any part of the solution will have the same composition as any other sample of the same solution. Two solutions made up of the same substances may, however, have different compositions. A solution of ammonia in water, for example, may contain 1% ammonia by mass, or 2%, 5%, 20.3%. up to the 29% solution called concentrated ammonia. This leads to variable physical properties, which are determined by the mixture s composition. 

A solution may exist in any of the three states—gas, liquid, or solid. Air is a gaseous solution made up of nitrogen, oxygen, argon, and other gases in small amounts. Like oxygen in water, dissolved carbon dioxide in carbonated beverages is a familiar liquid solution of a gas. Alcohol in water is an example of the solution of two liquids, and the oceans are liquid solutions of solids. Solid-state solutions are common in the form of metal alloys. 

Particle size distinguishes solutions from other mixtures. Dispersed particles in solutions, which may be atoms, ions, or molecules, are very small— generally less than 5 X 10 cm in diameter. Particles of this size do not settle on standing, and they are too small to see. 

Identify true statements, and rewrite the false statements to make them true. 

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Describe the characteristics of a solution and identify the various types. 

Selecting a Mobile Phase Based on Solvent-Solute Characteristics. The mobile phase in TLC is the source of mobility, but more importantly it produces selectivity. Selectivity—the degree of interaction between components of the mobile phase and analytes in the solute—determines the extent of any resolution that will be achieved. Solvent strength is the factor that determines mobility. Knowing the characteristics of a solute makes it easier to decide which solvents to try during the search for a mobile phase that will produce the desired separation. 

The entropy of a solution is itself a composite quantity comprising (i) a part depending only on tire amount of solvent and solute species, and independent from what tliey are, and (ii) a part characteristic of tire actual species (A, B,. ..) involved (equal to zero for ideal solutions). These two parts have been denoted respectively cratic and unitary by Gurney [55]. At extreme dilution, (ii) becomes more or less negligible, and only tire cratic tenn remains, whose contribution to tire free energy of mixing is... 

There are many laboratory methods for testing the relative merits of one defoamer against another. It is a simple matter to measure foam height as a function of time to compare the performance of various foam surfactants and defoamers. Unfortunately, this simplicity has led to a wide variety of methods and conditions used with no standard procedure that would make the measurement of foaminess as characteristic of a solution as its surface tension or viscosity. It has been suggested that the time an average bubble remains entrapped ia the foam is such a quantity (49), but very few workers ia the defoamer iadustry have adopted this proposal. Ia practice, a wide variety of methods are used that geaerally fall iato oae of five maia categories ... 

The more highly complexed hydrates of calcium chloride (CaCl2 nH2 O where n > 2) may also exhibit the characteristics of a Class 2 dryiag agent, because the hydrated species can physically absorb additional water to form a saturated solution. The term absorption is used to describe the phenomenon that occurs when a gas or vapor penetrates the soHd stmcture to produce a saturated solution ... 

It was shown in Chapter 7 that the performance of continuous crystallizers is determined by the characteristics of a feedback loop relating the output performance expressed as crystal size distribution and to the feed concentration and residence time. Thus, an increase in crystallizer residence time, or decrease in feed concentration, reduces the working level of supersaturation. This decrease in supersaturation results in a decrease in both nucleation and crystal growth. This in turn leads to a decrease in crystal surface area. By mass balance, this then causes an increase in the working solute concentration and hence an increase in the working level of supersaturation and so on. There is thus a complex feedback loop within a continuous crystallizer, as considered in Chapter 7 and illustrated in Figure 8.11. 

What evidence is there for the individual reaction steps The add-base reaction (Eq, 2) has the characteristics of a Broensted equilibrium, as has been shown in the case of diazomethane-benzoic acid (in toluene). Further evidence for this is provided by the reactions of diazoacetic ester and diazo ketones. The occurrence of free, mobile diazonium cations is also supported by the fact that solutions of diazomethane in methanol show greater conductivity than solutions of pure solvent. ... 

The characteristics of a polished surface are that it should be level on a macroscopic scale related, for example, to machine and grinding marks of 1-5 /im depth, and be smooth and bright on a microscopic scale typically 1-100 nm size for fine grained metal. To achieve dual levelling and smoothing a solution must satisfy three requirements by including three types of constituent ... 

If the set of experimental points plotted in Fig. 70 is compared with that of Fig. 51, it will be seen that the situation is very similar. Nor is this close resemblance accidental. It will be recalled that in equation (161) the term Be represents the type of term that would be characteristic of a solute of any kind, and that the situation in Fig. 51 arises from the superposition, on this term, of another term arising from the ionic character of the solute. When the interionic effects had been eliminated, ourin terest turned, in Chapter 9, to a discussion of the B-coefficients... 

A simple, reliable, and fast method of determining the pH of a solution and of monitoring a titration is with a pH meter, which uses a special electrode to measure H 0+ concentration. An automatic titrator monitors the pH of the analyte solution continuously. It detects the stoichiometric point by responding to the characteristic rapid change in pH (Fig. 11.9). Another common technique is to use an indicator to detect the stoichiometric point. An acid-base indicator is a water-soluble organic dye with a color that depends on the pH. The sudden change in pH... 

Finally, in instances in which a bulky solute molecule with several functional groups can be added to the system, a fragile sort of structure can be built up by simultaneous attachment of these molecules to create a network with the characteristics of a gel. This system is then permanently metastable toward settling and caking, but may not withstand the ravages of shear or high temperature. 

The most obvious characteristic of a solution of a high polymer is that its viscosity is considerably higher than that of the pure solvent, even when the concentration of polymer is quite small [22], The suggestion was first made by Staudinger in 1930 [1,2] that the relative magnitude of this increase in viscosity could be quantitatively correlated with the molecular weight of the polymeric solute. 

The purpose of a detector is to monitor the carrier gas as it emerges from the column and respond to changes in its composition as solutes are eluted. Ideally a detector should have the following characteristics rapid response to the presence of a solute a wide range of linear response high sensitivity stability of operation. 

The most important characteristic of a solution is its composition, i.e. the concentration of the different components of the phase. The composition of a solution is best expressed by the ratio of the number of moles of each component to the total number of moles. This measure of the composition is the mole fraction of a component. In the case of a binary solution consisting of the components A and B, the mole fractions of the two components are defined as... 

An important characteristic of a solution with regard to its LS is the specific refractive index increment dn/dc (frequently denoted also by the symbol v). As will... 

The concentration of a solute or adsorbate may be a nontrivial function of the distance to the surface, a function which contains information about the thermodynamics of the surface interaction. To explore the fluorophore concentration C(z) as a function of distance z from the surface, one can record the observed fluorescent intensity F as the characteristic depth d of the evanescent wave is varied. The mathematics of this is discussed immediately following Eqs. (7.44) and (7.45) above. 

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