Salt solution calculation

C03-0121. For each of the following salt solutions, calculate the amounts in moles and the numbers of each type of... 

C03-0122. For each of the following salt solutions, calculate the amounts in moles and the numbers of each type of Ion (a) 2.87 L of 0.0550 M lithium carbonate (b) 325 mL of a solution that contains 1.02 X lO formula units of sodium hydrogen sulfate and (c) 2.55 mL of a solution that contains 263 mg/L of sodium oxalate. 

SOLUBILITY OF A WEAK ELECTROLYTE IN SALT SOLUTIONS. Calculation of the solubility of a volatile strong electrolyte, such as HCl, in aqueous salt solutions is straightforward. However, solubilities of weak electrolytes are more difficult to model accurately, since the dissolved speciation must frequently be determined in addition to the activity of the component of interest. Thus, in the case of NH3, the relevant ionic interactions involving NH4 and OH" must be known in addition to parameters for the interaction of dissolved salts with the neutral NH3 molecule. See, for example, the work of Maeda et al. (47) on the dissociation of NH3 in LiCl solutions. 

EXAMPLE 13.9-1. Calculation of Osmotic Pressure of Salt Solution Calculate the osmotic pressure of a solution containing 0.10 g mol NaCl/1000 g HiO at 25°C. 

The thickness of the equivalent layer of pure water t on the surface of a 3Af sodium chloride solution is about 1 A. Calculate the surface tension of this solution assuming that the surface tension of salt solutions varies linearly with concentration. Neglect activity coefficient effects. 

Water Transport. Two methods of measuring water-vapor transmission rates (WVTR) ate commonly used. The newer method uses a Permatran-W (Modem Controls, Inc.). In this method a film sample is clamped over a saturated salt solution, which generates the desired humidity. Dry air sweeps past the other side of the film and past an infrared detector, which measures the water concentration in the gas. For a caUbrated flow rate of air, the rate of water addition can be calculated from the observed concentration in the sweep gas. From the steady-state rate, the WVTR can be calculated. In principle, the diffusion coefficient could be deterrnined by the method outlined in the previous section. However, only the steady-state region of the response is serviceable. Many different salt solutions can be used to make measurements at selected humidity differences however, in practice,... 

Bell has calculated Hq values with fair accuracy by assuming that the increase in acidity in strongly acid solutions is due to hydration of hydrogen ions and that the hydration number is 4. The addition of neutral salts to acid solutions produces a marked increase in acidity, and this too is probably a hydration effect in the main. Critchfield and Johnson have made use of this salt effect to titrate very weak bases in concentrated aqueous salt solutions. The addition of DMSO to aqueous solutions of strong bases increases the alkalinity of the solutions. 

After 6 hours the calculated amount of hydrogen has been taken up. The residue obtained after filtering and evaporating is taken up in benzene and extracted twice with diluted sodium carbonate solution. The alkali extract is then made acid to Congo red with 6N hydrochloric acid and the precipitate is taken up in ethyl acetate. The solution obtained is washed twice with salt solution, dried with sodium sulfate and evaporated. The residue is recrystallized from ether/petroleum ether. 1-(p-hydroxyphenyl)-2-phenyl-4-n-butyl-3,5-dioxo-pyrazolidine melts at 124° to 125°C. 

In the case of aqueous salt solutions, the observed molecular lowering was invariably greater than the calculated. In this case we put instead of (4) ... 

In a recent study of the transport of coarse solids in a horizontal pipeline of 38 mrrt diameter, pressure drop, as a function not only of mixture velocity (determined by an electromagnetic flowmeter) but also of in-line concentration of solids and liquid velocity. The solids concentration was determined using a y-ray absorption technique, which depends on the difference in the attenuation of y-rays by solid and liquid. The liquid velocity was determined by a sail injection method,1"1 in which a pulse of salt solution was injected into the flowing mixture, and the time taken for the pulse to travel between two electrode pairs a fixed distance apart was measured, It was then possible, using equation 5.17, to calculate the relative velocity of the liquid to the solids. This relative velocity was found to increase with particle size and to be of the same order as the terminal falling velocity of the particles in the liquid. 

To calculate the pH of a salt solution, we can use the equilibrium table procedure described in Toolboxes 10.1 and 10.2—an acidic cation is treated as a weak acid and a basic anion as a weak base. However, often we must first calculate the Ka or Kh for the acidic or basic ion. Examples 10.10 and 10.11 illustrate the procedure. 

EXAMPLE 10.10 Calculating the pH of a salt solution with an acidic cation... 

Using this approach, calculations can be made of volumetric, entropic and energy parameters taking account of the effect of overlapping cospheres. Some indication of the organization in the solution is also possible. The properties of a number of concentrated salt solutions have been analysed by this procedure, including simple 1 1 salts, alkaline earth salts and alkylammonium salts. 

Osmotic Pressure The osmotic pressure 7i of salt solutions is calculated from... 

Figure 7.7 shows the calculated ratio / of the average concentration for cations and anions within the intermolecular spaces before hybridization and after hybridization . The ratio / is plotted as a function of the DNA cell radius Rs and for 1 1 salt solutions of different bulk-ion concentrations of n() = 0.005, 0.15 (physiological solution) and 0.5 M, respectively. The fraction of both the ssDNA and dsDNA charge compensated by the condensed cations was taken as 0 = 0.8. Two effects can be recognized from Fig. 7.7 ... 

Knowing the value of the solubility product constant can also allow us to predict whether or not a precipitate will form if we mix two solutions, each containing an ion component of a slightly soluble salt. We calculate the reaction quotient (many times called the ion product), which has the same form as the solubility product constant. We take into consideration the mixing of the volumes of the two solutions, and then compare this reaction quotient to the K.p. If it is greater than the Ksp then precipitation will occur until the ion concentrations reduce to the solubility level. 

Equilibrium constants calculated from the composition of saturated solutions are dependent on the accuracy of the thermodynamic model for the aqueous solution. The thermodynamics of single salt solutions of KC1 or KBr are very well known and have been modeled using the virial approach of Pitzer (13-15). The thermodynamics of aqueous mixtures of KC1 and KBr have also been well studied (16-17) and may be reliably modeled using the Pitzer equations. The Pitzer equations used here to calculate the solid phase equilibrium constants from the compositions of saturated aqueous solutions are given elsewhere (13-15, 18, 19). The Pitzer model parameters applicable to KCl-KBr-l O solutions are summarized in Table II. 

We have used these average differences between potassium and ammonium salt solutions and between sodium and ammonium salt solutions to calculate average values of salting-out coefficients for the four gases in ammonium salts from determinations on salts with the same anion but different cations. A sample calculation from data on ammonia in bromide solutions is shown in Table VI. 

Figure 2. Comparison of the calculated and experimental activity of water for water-salt solutions over the full range of composition...

In the equations developed by Reilly and Wood (15) from the cluster Integral model (1 6), y+ is calculated in complex solutions from excess properties of single salt solutions. Note that the cluster Integral approach 1s based upon terms which represent the contributions of pair-wise ion interactions 1n various types of clusters to the potential interaction energy. Then, the partition function and the excess properties of the solution can be evaluated. The procedure is akin to the vlrial expansion 1n terms of clusters. 

In this section, you learned why solutions of different salts have different pH values. You learned how to analyze the composition of a salt to predict whether the salt forms an acidic, basic, or neutral solution. Finally, you learned how to apply your understanding of the properties of salts to calculate the pH at the equivalence point of a titration. You used the pH to determine a suitable indicator for the titration. In section 9.2, you will further investigate the equilibria of solutions and learn how to predict the solubility of ionic compounds in solution. 

For aqueous solutions of electrolytes, a concise method of tabulating such entropy data is in terms of the individual ions, because entropies for the ions can be combined to give information for a wide variety of salts. The initial assembling of the ionic entropies generally is carried out by a reverse application of Equation (7.26) that is, Af6m of a salt is calculated from known values of AfG and AfFT for that salt. After a suitable convention has been adopted, the entropy of formation of the... 

Soil. In soils, phosmet is rapidly hydrolyzed to phthalimide (Camazano and Martin, 1980 S nchez-Camazano and S nchez-Martin, 1983). The rate of hydrolysis is greater in the presence of various montmorillonite clays and chloride salts. The calculated hydrolysis half-lives of phosmet in the presence of calcium, barium, copper, magnesium, and nickel montmorillonite clays were 0.084, 0.665, 10.025, 16.926, and 28.738 d, respectively. Similarly, the half-lives of phosmet in the presence of copper, calcium, magnesium, and barium chlorides were <0.020, 5.731, 10.680, and 12.242 d, respectively. In comparison, the hydrolysis of phosmet in a neutral water solution was 46.210 d (Sanchez-Camazano and S nchez-Martin, 1983). 

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