Concentrations in solutions

Both molarity and formality express concentration as moles of solute per liter of solution. There is, however, a subtle difference between molarity and formality. Molarity is the concentration of a particular chemical species in solution. Formality, on the other hand, is a substance s total concentration in solution without regard to its specific chemical form. There is no difference between a substance s molarity and formality if it dissolves without dissociating into ions. The molar concentration of a solution of glucose, for example, is the same as its formality. 

Microchemical or ultramicrochemical techniques are used extensively ia chemical studies of actinide elements (16). If extremely small volumes are used, microgram or lesser quantities of material can give relatively high concentrations in solution. Balances of sufficient sensitivity have been developed for quantitative measurements with these minute quantities of material. Since the amounts of material involved are too small to be seen with the unaided eye, the actual chemical work is usually done on the mechanical stage of a microscope, where all of the essential apparatus is in view. Compounds prepared on such a small scale are often identified by x-ray crystallographic methods. 

The structure of these products is uncertain and probably depends on pH and concentrations in solution. The hydroxyl or carboxyl or both are bonded to the titanium. It is likely that most, if not all, of these products are oligomeric in nature, containing Ti—O—Ti titanoxane bonds (81). Thek aqueous solutions are stable at acidic or neutral pH. However, at pH ranges above 9.0, the solutions readily hydroly2e to form insoluble hydrated oxides of titanium. The alkaline stabiUty of these complexes can be improved by the addition of a polyol such as glycerol or sorbitol (83). These solutions are useful in the textile, leather (qv), and cosmetics (qv) industries (see Textiles). 

BBT solution on unmodified sorbents of different nature was studied. Silica gel Merck 60 (SG) was chosen for further investigations. BBT immobilization on SG was realized by adsoi ption from chloroform-hexane solution (1 10) in batch mode. The isotherm of BBT adsoi ption can be referred to H3-type. Interaction of Co(II), Cu(II), Cd(II), Ni(II), Zn(II) ions with immobilized BBT has been studied in batch mode as a function of pH of solution, time of phase contact and concentration of metals in solution. In the presence of sodium citrate absorbance (at X = 620 nm) of immobilized BBT grows with the increase of Cd(II) concentration in solution. No interference was observed from Zn(II), Pb(II), Cu(II), Ni(II), Co(II) and macrocomponents of natural waters. This was assumed as a basis of soi ption-spectroscopic and visual test determination of Cd(II). Heavy metals eluted from BBT-SG easily and quantitatively with a small volume of HNO -ethanol mixture. This became a basis of soi ption-atomic-absoi ption determination of the total concentration of heavy metals in natural objects. 

The EPA defines corrosivity in terms of pH (i.e., wastes with pH <2 or >2.5) or in terms of ability to corrode steel (SAE 20) at a rate of >6.35 mm (0.250 in.) per year at a temperature of 55 C (13°F). This discussion will address corrosivity as it applies to acids and caustics. Acids are compounds that yield H ions (actually HjO ions) when dissolved in water. Common industrial acids include acetic, nitric, hydrochloric, and sulfuric acids. The terms concentrated and dilute refer to the concentrations in solution. Mixing a concentrated acid with enough water will produce a dilute acid. For example, a bottle of concentrated HCl direct from the manufacturer is approximately 12 N in HCl, while a solution of HCl used in a titration may be only 0.5 N. The latter is a dilute acid solution. 

Estimation of Protein Concentrations in Solutions of Biological Origin... 

C 0.5012 mol 2 at 15°C). It is clearly unwise to associate a pH meter reading too closely with pH unless under very controlled conditions, and still less sensible to relate the reading to the actual hydrogen-ion concentration in solution. For further discussion of pH mea.surements, see Pure Appl. Chem. 57, 531-42 (1985) Definition of pH Scales, Standard Reference Values, Measurement of pH and Related Terminology. Also C E News, Oct. 20. 1997. p. 6. 

Rosenfel d" considers that SO2 can act as a depolariser of the cathodic process. However, this effect has only been demonstrated with much higher levels of SO2 (0-5%) than are found in the atmosphere (Table 2.4) and the importance of this action of SO2 has yet to be proved for practical environments. However, SO2 is 1 300 times more soluble than O2 in water" and therefore its concentration in solution may be considerably greater than would be expected from partial pressure considerations. This high solubility would make it a more effective cathode reactant than dissolved oxygen even though its concentration in the atmosphere is comparatively small. 

Temperature is the most important of the factors affecting pickle activity. In general, an increase of 10°C causes an increase in pickling speed of about 70 Vo. Agitation of the pickle increases the speed since it assists the removal of the insoluble scale and rapidly renews the acid at the scale surface. Increase in acid concentration up to about 40 Vo w/w in ferrous sulphate-free solutions, and up to lower concentrations in solutions containing ferrous sulphate, increases the activity. Increase in the ferrous sulphate content at low acid concentrations reduces the activity, but at 90-95 C and at acid concentrations of about 30 Vo w/w it has no effect. 

Given the ionization constant of a weak acid and its original concentration, the H+ concentration in solution is readily calculated. The approach used is the inverse of that followed in Example 13.5, where Kz was calculated knowing [H+] here, K is known and [H+] must be calculated. 

Here we have two opposing processes. At a given temperature, molecules leave the surface of the crystal at a constant rate, tending to increase the concentration in solution. On the other hand, dissolved molecules are continually striking the surface and precipitating, tending to... 

Here Yi and y2 are the activity coefficients of ions in solution, y, and y2 are the coefficients of resin activity, cx and c2 are ion concentrations in solution, ntj and m2 are fixed ion concentrations (exchange or weight concentrations) and Ks is the concentration constant of ion exchange, the selectivity constant. 

The degree of saturation of carboxylic CP with protein (Y) is determined by the ratio of the amount of protein bonded under these conditions (at a predetermined concentration in solution) to the maximum amount Y = m/M. In this case, Hill s equation becomes... 

Hence, Flory s theory offers an objective criterion for chain flexibility and makes possible to divide all the variety of macromolecules into flexible-chain (f > 0.63) and rigid-chain (f < 0.63) ones. In the absence of kinetic hindrance, all rigid-chain polymers must form a thermodynamically stable organized nematic phase at some polymer concentration in solution which increases with f. At f > 0.63, the macromolecules cannot spontaneously adopt a state of parallel order under any conditions. 

The study of carbonate complexes of Pu is complicated by various experimental difficulties. The low solubility of many carbonates (7), leaving a very dilute Pu concentration in solution, results in difficulties to the experiments with electrochemical or spectrophotometric methods. However, the radiometric method with solvent extraction or solubility measurement is easily applicable for the purpose. Unlike the solution with anions, like Cl, N03 etc., the concentration of which can be varied at a constant pH, the preparation of solutions with varying carbonate concentration accompanies indispensably the change of pH of the solution. As a result, the formation of carbonate complexes involves accordingly the hydrolysis reactions of Pu ions in solutions under investigation. It is therefore prerequisite to know the stability constants of Pu(IV) hydroxides prior to the study of its carbonate complexation. 

A practically unlimited source of plutonium was present, so that its concentration in solution (dissolved or otherwise dispersed) could, at least in theory, increase continuously with time until a steady-state situation was reached. 

Our first task is to calculate the pH of a solution of a weak acid, such as acetic acid in water The initial concentration of the acid is its concentration as prepared, as if no acid molecules had donated any protons. For a strong acid HA, the H30+ concentration in solution is the same as the initial concentration of the strong acid, because all the HA molecules are deprotonated. However to find the H30 concentration in a solution of a weak acid HA, we have to take into account the equilibrium between the acid HA, its conjugate base A-, and water (Eq. 8). We can expect the pH to lie somewhere between 7, a value indicating no deprotonation, and the value that we would calculate for a strong acid, which undergoes complete deprotonation. The Technique, which is based on the use of an equilibrium table like those introduced in Chapter 9, is set out in Toolbox 10.1. 

As an example, the migration of clay from the surface of a soil to a lower horizon results from several processes occurring when certain soil and environmental properties exist. First, claysized minerals must form, usually requiring weathering to have occurred. Clay minerals formed in the surface soil can then go into suspension when salt concentrations in solution are low. Seasonal rains can move the clay down... 

If metal concentrations in solution become large, soluble complexes that contain more than one metal ion can form. Eventually these... 

The variation of enantioselectivities with temperature and pressure was investigated. The effects of these two factors are very substrate dependent and difficult to generalize even in a single substrate serie. However, it seems that enantioselectivities are shghly better at 25-40 °C than at lower temperatures (0 °C or less). The stereoselectivity can be inverted for specific alkenes (formation of the S or R enantiomer preferentially). For several substrates, the reactions tend to proceed to completion with optimal ee s when performed at lower hydrogen pressure (2 bar) instead of 50 bar (Fig. 13). Pronoimced variation of enantioselectivities with hydrogen concentration in solution may indicate the presence of two (or even more) different mechanisms which happen to give opposite enantiomers for some substrates. 

To determine the stability of the Fe-B nanocomposite as a heterogeneous photo Fenton catalyst, the Fe concentrations in solution after 120 minutes were measured by ICP. The results obtained indicate that the Fe concentration in solution after 20 minutes reaction is less than 1 mg/L, which is negligible. 

The adsorption isotherms for each chemical, Triton X-100 or phenanthrene, on the activated carbons were shown in Figs. 1 and 2. The adsorption isotherms are expressed as qg [g g ], the amount of compounds adsorbed per unit mass of adsorbent, as a fimction of Q [g l ], the concentration in solution at equilibrium [5, 6]. The best-fit parameters for Freimdlich isotherms (g = or linear isotherms (q - Kj C ) were summarized in Table 2. The... 

Figure 12-10 is a molecular view showing that the equilibrium concentration of a dissolved gas varies with the partial pressure of that gas. An increase in the partial pressure of gas results in an increase in the rate at which gas molecules enter the solution. This increases the concentration of gas in solution. The increased concentration in solution, in turn, results in an increase in the rate at which gas molecules escape from the solution. Equilibrium is reestablished when the solute concentration is high enough that the rate of escape equals the rate of capture. 

---