Properties of NaCl

It is also not practical to expect that a single equation will correlate simultaneously the properties of NaCl with hexane, since there are too many differences between them. When we study the properties within a homologous series, such as the normal paraffins that differ only in the number of —CH2—units, we isolate only one parameter to study. In many cases, the molecular properties change smoothly with the number of units, which can be used as the predictor. The one-parameter populations set out in table 5.4 are frequently used. 

Hameri, K., M. J. Rood, and H.-C. Hansson, Hygroscopic Properties of NaCl Aerosol Coated with Organic Compounds, . /. Aerosol Sci., 23, Suppl. 1, S437-S440 (1992). 

Using the values of the coefficients given by Silvester and Pitzer while holding b and a constant at the T = 298.15 K values, the thermodynamic properties of NaCl solutions as a function of molality are reproduced within experimental error over the temperature range from 273.15 K to 573.15 K. 

We will not attempt to reproduce Archer s equations here. A total of 108 coefficients are present in the equations. Fortunately, many of these coefficients are not needed to fit the data and are set equal to zero. Archer, in his analysis of NaCl solutions, used 54 of the coefficients in his fit. He shows in his paper that his equations with these coefficients accurately summarize the properties of NaCl solutions over the pressure, temperature, and molality range given above. 

D. G. Archer, Thermodynamic properties of the NaCl + H20 system. II. Thermodynamic properties of NaCl(aq), NaCl-2H20(cr), and phase equilibria , J. Phys. Chem. Ref. Data, 21, 793-829 (1992). 

Designing experiments Describe how you could use the properties of the compounds to test the purity of your recovered samples. If your teacher approves your plan, use it to check your separation of the mixtures. (Hint Check a chemical handbook for more information about the properties of NaCl and KNO3.)... 

The high strength of its ionic bonds results in all of the following properties of NaCl EXCEPT... 

Look up the properties of NaCl and PCI3 in a handbook of chemistry. Why do we describe NaCl as an ionic compound and PCI3 as a covalent compound ... 

The problem with this procedure is that it adds more parameters, although not as many as might be expected, since derivatives of equations (18.46) to (18.48) using equations (18.33), (18.36), and (18.37) give the thermal coefficients / <0>L, /7(I)L, Bj x, and C ,x. Silvester and Pitzer use a total of 16 parameters to represent the thermodynamic properties of NaCl(aq) as a function of the temperature from 273.15 to 573.15 K and molalities from 0 to that of the saturated solution at p = 0.1 MPa (or the saturation vapor pressure). 

Up to 300 C, the overall regression included values at pressures to 1 kb. At 350 C, however, only volumetric data at pressures less than or equal to 200 bars were included because the simple pressure function given by Equation 19a is inadequate to fit the 350 C data over the whole pressure range. The parameters for Equation 19 for v/, Wj, and Uj evaluated from the volumetric data are given in Table II. With this set of parameters it is possible to recalculate various thermodynamic properties of NaCl(aq) solutions to a reference pressure, chosen here to be 200 bars. Because the volumetric data for KCl solutions are more limited in concentration range and are less precise than those for NaCl solutions (9) a separate evaluation of KCl(aci) volumetric data was not done. Instead, the pressure dependence of KCl(aq) properties was approximated using values for NaCl(ac ). This procedure has been shown to be successful forNa2S04(aq) (13). 

Extensions beyond the data base of (2) are largely untested and include additions to PITZER.DATA for (1) the calculation of the thermodynamic properties of aqueous solutions containing Fe(II), Mn(II), Sr +, Ba2+, Li+, and Br (2) the estimation of the temperature dependence of many of the single-salt parameters from selected literature data and (3) the calculation of the thermodynamic properties of NaCl solutions to approximately 300 °C along the vapor pressure curve of water beyond 100 C (18)-Except for the NaCl-H20 system, the PHRQPITZ aqueous model should not be used outside the temperature range 0 to 60 C. Several recent evaluations of the temperature dependence of Pitzer interaction parameters to relatively high temperatures (19-21) have not yet been incorporated in the PHRQPITZ data base. 

The work by Aguirre de Career et al, (1993) on dosimetric properties of NaCl Eu + irradiated by Uy X, 3 and a radiations will be described in some detail. 

Apra E, Causa M, Prencipe M, Dovesi R, Saunders VR (1993) On the structural properties of NaCl an ab initio study of the B1-B2 phase transition. J Phys Condens Matter 5 2969... 

C are fitted as a function of pressure and temperature. Usually the precision of the high temperature volumetric data does not justify the use of a second virial parameter dependent of the concentration and is taken as zero. For instance, to describe the volumetric properties of NaCl up to 250°C and 40 MPa (Simonson e a/., 1994), 14param-eters are needed for fitting VI, and O. This behavior is also observed for HCl (Sharygin and Wood, 1997) up to 350 °C and 28 MPa and for CaCl2 (Oakes et al, 1995b) up to 250 °C and 40 MPa, which requires 20 and 24 parameters, respectively. Thus, the extrapolation of the volumetric properties beyond the temperature and pressure range where these parameters were adjusted is not reliable. 

Sedlbauer and Wood (2004) used the MSA model to describe the tiiermodynamics properties of NaCl near the critical point. In this case the crystallographic diameters of the ions were used along with a model (Sedlbauer et al, 2000) for the standard state term. The MSA model without adjustable parameters provides a better fit of the partial molar volume than the Pitzer model. 

The physical significance of each of these parameters was discussed by Pitzer (1986, 1989, 1990, 1998) and Tanger and Pitzer (1989). Hovey et al. (1990) have correlated the measurements of isothermal vapor-hquid compositions for H2O + KCl and H2O + NaCl using the equation of state (2.47). An equation of state (2.47), which was originally proposed by Pitzer (1986) was improved and used by Tanger and Pitzer (1989) to describe the pTx properties of NaCl(aq) and KCl(aq) solutions. The Pitzer-Tanger-Hovey (PTH) EOS (Hovey et al, 1990) for H2O + NaCl solutions is based on an expansion of pressure aroimd the critical point of pure water (see Equation (2.47)). Only a few simple terms of the expansion were used for the H2O + NaCl solution, and the equation of Haar et al. (1984) was used to calculate the properties of pure water. The theoretical basis for the PTH EOS Hovey et al. (1990) is given in the work by Pitzer (1986) and Pitzer et al. (1987). Hovey et al (1990) pre-... 

Waldbaum (1969). The thermodynamic mixing properties of NaCl-KCl liquids are treated by combining observed liquidus data with the calculated results of Thompson and Waldbaimi (1969b) for subsolidus mixing in the alkali halide system. The analysis follows the equations used by Waldbaum and Thompson (1969), but Waldbaimi casts the Margules equation in terms of the composition of the liquidus minimimi in order to utilize the best data available. 

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