Argon in water

Dediazoniations that follow a homolytic mechanism are, however, always (as far as they are known today) faster than heterolytic dediazoniations. A good example is afforded by the rates in methanol. In a careful study, Bunnett and Yijima (1977) have shown that the homolytic rate is 4-32 times greater than the heterolytic rate, the latter being essentially independent of additives and the atmosphere (N2, 02, or argon). In water the rate of heterolytic dediazoniation, measured at pH <3, is lower than that of the homolytic reactions that take place in the range pH 8-11 (Matrka et al., 1967 Schwarz and Zollinger, 1981 Besse and Zollinger, 1981). 

This small volume of air, ignored for a hundred years by later experimenters, was presumably argon and its related gases. That Cavendish s estimate of 1/120 of the volume of the nitrogen used, or. 65 volume per cent of the atmosphere, is smaller than the actual content (about. 93 volume percent as at present determined) is doubtless due to the fact of the solubility of argon in water. 

Weiss, R. F. (1970a) The solubility of nitrogen, oxygen and argon in water and seawater. Deep Sea Res., 17, 721-35. 

Compared with ambient values, the specific heat capacity of water approaches infinity at the critical point and remains an order of magnitude higher in the critical region [26], making supercritical water an excellent thermal energy carrier. As an example, direct measurements of the heat capacity of dilute solutions of argon in water from room temperature to 300 °C have shown that the heat capacities are fairly constant up to about 175-200 °C, but begin to increase rapidly at around 225 °C and appear to reach infinity at the critical temperature of water [29]. 

Another limiting case is the very dilute solution of s in phase fi, say, argon in water, for which we have the limiting form of equation (7.31) which reads... 

When investigating dilute solutions of, say, argon in water or xenon in organic solvents, the stated purpose of the investigators is to study the Gibbs... 

Extrapolate The solubility of argon in water at various pressures is shown in Figure 14.28. Extrapolate the data to 15 atm. Use Henry s law to verify the solubility determined by your extrapolation. 

A. Lannung, The solubilities of helium, neon and argon in water and some organic solvents, /ACS, 1930,52,67-80. 

Wang SL, Chen CT, Hong GH, Chung CS (2000) Carbon dioxide and related parameters in the East China Sea. Cont Shelf Res 20(4-5) 525-544 Weiss RF (1970) Solubility of nitrogen, oxygen and argon in water and seawater. Deep Sea Res 17(4) 721-731... 

Here, C , C , and C , are volume concentrations of total, atmo-spheric and radiogenic argon in water, respectively. 

Table 3.1 shows some values of the Ostwald absorption coefficient y of argon in water and in some liquids. It should be noted that the solubility as measured by y is about an order of magnitude smaller in water compared with other solvents. Note, however, that the solubility of argon in ethylene glycol at 25°C is about 0.035, almost the same as in water Isee Ben-Naim (1968)]. 

Table 3.1. Ostwald Absorption Coefficient y for Argon in Water and in Some Organic Liquids at Two Temperatures ...

Exercise E.3.9 Examine the following argument frequently made in the literature. The large positive value of AG of, say, argon in water is due to the large degree of structure. As temperature increases, the structure of water breaks down. Hence, we should expect that the value of AG will decrease upon the increase in temperature. Use the ideal mixture model to see why this conclusion is erroneous. 

This model was first studied by Lovett and Ben-Naim (1969). The entropy and the enthalpy of solvation were found to be large and negative, as are the corresponding values for the solvation of, say, argon in water. A major failure of the model discussed earlier is that the solvation Gibbs energy was found to be smaller... 

The second striking difference between the solubility of gases in water and in other solvents is the temperature dependence of the solubility. Figure 7.2 illustrates that difference for argon in water and in methanol. The steep decrease in the solubility (in terms of y) as a function of temperature is very characteristic of water. In other solvents, the solubility may either increase or decrease with temperature in both cases, it occurs with a relatively small slope. Figure 7.3 includes some further information on the temperature dependence of the solubility of methane (intermsofzl// ) in water and in a few other solvents. The difference in the temperature dependence of the solubility is also discernible from Table 7.1. 

Fig. 7.2. Temperature dependence of y for argon in water and in methanol. [Redrawn from Ben-Naim (1972e).]...

The partial molar heat capacity of gases is usually larger in water than in other solvents. This quantity is obtained from the second derivative of experimental curves and therefore is generally not very accurate. Nevertheless, the difference between water and other solvents is considered to be quite clear-cut. As an example, the partial molar heat capacity of argon in water at room temperature is about 50 cal/mole deg, whereas in ethanol, methanol, or p-dioxane, it is almost zero. Table 7.2 includes some information on the partial molar heat capacity of methane in water and in nonaqueous solvents. 

The difference between the standard energy and enthalpy of solution for process II (see Section 7.2) is quite small. As an example, for argon in water at 25°C, the standard enthalpy of solution is —2000 cal/mole. The value of P A at 1 atm... 

FIGURE 5.13 Calculated pair distribution functions for argon in water argon-oxygen and... 

Perhaps one of the most striking pieces of evidence that a simple solute has a significant effect on the structure of water comes from a comparison of the solvation entropy of KCl and argon in water. The corresponding values are (at 25°C)... 

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