Composition of a solution

A quantitative method for reporting the ionic composition of a solution that takes into account the greater effect of more highly charged ions (jr). 

The ionic composition of a solution frequently is expressed by its ionic strength, p,... 

It is convenient to have some uniform method of representing the composition of a solution, and for this purpose use is made of the so-called concentration of a component, which may be referred to the total mass, or to the total volume, or to the molecular constitution. 

What Are the Key Ideas Bronsted acids are proton donors Bronsted bases are proton acceptors. The composition of a solution of an acid or base immediately adjusts to satisfy the values of the equilibrium constants for all the proton transfer reactions taking place. 

When we visualize the molecular composition of a solution of a weak acid in water, we think of a solution that contains... 

FIGURE 19.5 The fractional composition of a solution of alanine, a typical amino acid, as a function of pH. Notice that the concentration of the molecular form is extremely low at all pH values its concentration had to be multiplied by a factor of 10 l for it to be visible on the graph. Amino acids are present almost entirely in ionic form in aqueous solution. 

The composition of a solution can vaiy, so we must specify the concentrations of solutes as well as their identities. There are several ways to express concentration, each having advantages as well as limitations. Any concentration value is a ratio of amounts. The amount of one component, usually a solute, appears in the numerator, and some other amount, describing either the solvent or the total solution, appears in the denominator. 

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... 

Similarly, GPTMS-based compositions of a solution of pre-hydrolysed GPTMS methyltrimethoxysilane (MTMS) hybrid doped with colloidal... 

Equilibrium composition of a solution in presence of CaCC>3(s) (calcite) at constant particle pressure of C02 (Pco2 = 10 3 5 atm) at 25° c-,f no ac d or base is added-the equilibrium composition is indicated by the arrow. The calcite at this composition is characterized by a net surface charge of zero. 

The simplest application of an electrolytic cell is the measurement of conductance. If a fixed voltage is applied to two electrodes which dip into a test solution, depending upon the conductivity of the solution, a current will flow between them. Although conductivity measurements do not give any information about the nature of the ions in the solution they can be used quantitatively. They are, however, more frequently used to monitor the changing composition of a solution during a titration. 

Concentration is the most common means for describing the composition of a solution in biochemistry. Enzyme kinetic expressions are typically expressed in these concentration units. Unless otherwise noted, this is the method used throughout this text. Nevertheless, other methods for describing compositions are utilized. For example, mole fractions are often used in Job plots. Gases in solution are commonly measured in terms of partial pressures. Below is a brief description of a few of these other conventions or methods. 

A measure of the fractional composition of a solution containing one or more substances in amounts, ne, nc,.. . (where in the amount-of-substance i expressed in mol), such that for any component, say B ... 

A further method for the specification of the composition of a solution or mixture, related to the molar scale, is the volume fraction of the solute, ( ). This takes into account any change in the volume of the system that has taken place on the preparation of the solution-the volume (change) of mixing. Therefore for a solute I ... 

The composition of a solution of 3-O-methyl-D-psicose15 at 27° is 31 7 56 6, whereas that of D-psicose is 22 24 39 15. In this case, the methoxyl group in the / -pyranose form (17) is axial, and 1,3-parallel interaction with one of its equatorial neighbors cannot be avoided. There is a similar interaction in the / -furanose form, too, but not in the a anomers. 

Replacement of a hydroxyl by an amino group may cause profound changes in the composition of a solution of a sugar. The extent of the change depends on whether the amino group is free, protonated, or acylated and, even more, on which hydroxyl group has been thus re-... 

Fusion of an oxirane ring to a pyranose ring also deforms it, and thereby lowers its stability. The composition of 2,3-anhydro-D-mannose in aqueous solution,165 as determined by g.l.c. of the trimethylsilyl derivatives, is 23 7 65 5. This is remarkably similar to the composition of a solution of 2,3-O-isopropylidene-L-rhamnose. For 2,3-anhydro-D-allose, the ratios are166 41 12 5 42 (or 41 5 12 42). In this case, although the proportion of furanose forms is substantial, there is no clear preponderance of the //-furanose form, presumably because OH-1 and OH-2 are trans but OH-1 is quasi-equatorial by contrast, in the (preponderant)... 

Steps 1 and 6 are the heart of the problem. Guessing what chemical equilibria exist in a given solution requires a fair degree of chemical intuition. In this book, you will usually be given help with step 1. Unless we know all the relevant equilibria, it is not possible to calculate the composition of a solution correctly. Because we do not know all the chemical reactions, we undoubtedly oversimplify many equilibrium problems. 

The principal species of a monoprotic or polyprotic system is found by comparing the pH with the various pKa values. For PH < pKh the fully protonated species, H A, is the predominant form. For pA) < pH < pK2, the form H , A is favored and, at each successive pK value, the next deprotonated species becomes principal. Finally, at pH values higher than the highest pK, the fully basic form (A"-) is dominant. The fractional composition of a solution is expressed by a, given in Equations 10-17 and 10-18 for a monoprotic system and Equations 10-19 through 10-21 for a diprotic system. 

Figure 1. pH dependence of the computed composition of a solution, which was 0.01 M nickel(ll)nitrate and 0.03M l-serine, at 37°C and 0.15M potassium nitrate, using the values in Table I... 

Calculate the vapor pressure and composition of a solution of two liquids, Self-Test 8.16. 

Because conjugate acids and bases are in equilibrium in solution, we can express the composition of a solution of an acid or base in terms of the equilibrium constant for the proton transfer. For example, for acetic acid in water,... 

For another change of state, we consider the change of composition of a solution from one composition to another represented by the equation... 

Whereas the basic principles for calculating the composition of a solution in equilibrium with a carbonate mineral are relatively straightforward, the application of these types of calculations to real world situations is commonly less obvious and fraught with difficulties. Consequently, we will present a series of calculations applied to natural geochemical systems, inspired by those originally... 

In the present work the possibility to produce fullerene-containing coatings on the nickel electrodes by the electrochemical method has been studied depending on the chemical composition of a solution and synthesis conditions in particular the cell voltage. 

Response time — Although this is often used as a synonym for -> time constant of an - exponential decay, it has a more general meaning For an exponential decay following the differential equation dx/df = -Ax and having the solution x = x0e-/U the - time constant is r = A-1. Of course, beside the time constant t, any other values can be defined for specified ratios of xq/x, e.g., xo/x = 0.5, or x0/x = 0.1, etc. The term response time is frequently used in connection with - electrochemical detectors (and generally for detectors) when their ability to respond to a change of chemical composition of a solution has to be characterized. Supposed the concentration can be stepped with infinite speed from a small... 

These units are infrequently used but are of great convenience in expressing the overall composition of a solution when the solute is partially associated or dissociated. 

The composition of a solution can be described in many different ways, as we will see in Chapter 17. At this point we will consider only the most commonly used expression of concentration, molarity (M), which is defined as moles of solute per volume of solution (expressed in liters) ... 

Mole per cent or mole fraction, weight per cent or weight fraction, and volume per cent or volume fraction may be employed to designate the composition of a solution. Avogadro s Law is not applicable to liquids, and equal volumes of different liquids do not contain the same number of molecules. Consequently, mole per cent and volume per cent are not equivalent in liquid solutions as they were in perfect-gas mixtures. To convert mole per cent to weight per cent the procedure is identical with that previously described for gases. To calculate the volume per cent of a liquid solution from the mole per cent or weight per cent the densities of the pure components must be known. 

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