Nitrogen, fugacity

Fio. 10. Solubility of nitrogen in water at high pressures. Fugacity is in atmospheres. 

To illustrate this thermodynamic consistency test, Figs. 15, 16, and 17 show plots of the appropriate functions needed to calculate Areas I, II, and III, respectively, for the nitrogen-carbon dioxide system at 0°C the data are taken from Muirbrook (M5). Fugacity coffiecients were calculated with the modified Redlich-Kwong equation (R4). 

The feed stream consists of 60 mole percent hydrogen, 20% nitrogen, and 20% argon. Calculate the composition of the exit gases, assuming equilibrium is achieved in the reactor. Make sure that you take deviations from the ideal gas law into account. The equilibrium constant expressed in terms of activities relative to standard states at 1 atm may be assumed to be equal to 8.75 x 10 3. The fugacity of pure H2 at 450 °C and 101.3 MPa may be assumed to be equal to 136.8 MPa. 

If the gas mixture is considered to be an ideal gas mixture then all fugacity coefficients are 1 and since K is a constant, the effect of increasing pressure is an increase of the equilibrium mole fraction of ammonia and a decrease of the mole fractions of nitrogen and hydrogen. However, since the ammonia synthesis is a high pressure process the gas mixture is not an ideal gas and the fugacity coefficients have to be taken into account. 

Indeed, the constant k in (296) and (297) characterizes only the rates of adsorption and desorption of nitrogen and is thus one and the same for both reactions. The difference in the rates of these reactions results only from the nonidentity of the fugacities of adsorbed nitrogen pNl and pf,2, the last being determined for reaction (314), instead of (298) by the equation... 

The three seminal ideas in this early work of Temkin are quite general. The first is that adsorption of nitrogen is rate determining. The second is the virtual pressure or fugacity of adsorbed nitrogen, a concept of great importance to the understanding of catalytic cycles at the steady state. The third idea is the kinetic description of the catalytic surface as a nonuniform one. The last was systematized later by Temkin s school, both in theory and in application, to a... 

N (g), we obtain A H = -153.69 0.75 kcal mol" at unit fugacities of oxygen and nitrogen. When this value is combined... 

Problem Utilize the following data to calculate the fugacities of nitrogen gas at the various pressures at 0° C. 

Determine by the graphical method the fugacity of nitrogen in the mixture at the various total pressures, and compare the results with those obtained for the pure gases hence, test the Lewis-Randall rule for the fugacity of a gas in a mixture [cf. Merz and Whittaker, J, Am. Chem, Soc., 50, 1522 (1928)]. 

It can be shown that the maximum conversion of nitrogen and hydrogen into ammonia occurs when the gases are mixed with the stoichiometric ratio. (See Problem PI5.1.) hSee Section 11.3a of Chapter 11 for a discussion of the effect of pressure on the fugacity, including the Lewis and Randall rule. 

Fugacities calculated using this equation for nitrogen at 273 K are compared with the exact values in Table 8.1. 

With this equation /can be calculated at a particular temperature and pressure. This can be done if the molar volume V of the gas is known as a function of the pressure P at the specified temperature. To give an example, nitrogen at 25°C and 1000 atm is well away from ideality. The ideal pressure (nRT/V) is 498 atm, but the fugacity is in fact 1839 atm. 

Figaie 1.2-2 shows the fugacity of nitrogen at 100 K. as computed from Eqs. (1.2-30), (1.2-32), and (1.2-33). Also shown are several oommonly employed approximations. The dashed line/f = P is the ideal-gas approximation to the vapor fugacity it is a special case of Eq. (1.2-26) and Is a consequance of the definition, Eq. (1.2-28). Note that the idenl-gas approximation becomes asymptotically valid as P approaches zero. 

With v, taken as the molar volume of the saturated liquid, relative fugacities computed from Eq, (1.2-34) for subcooled liquid nitrogen at 100 K produce results nearly identical lo those given by the solid curve in Fig. 1.2-2. 

Foam fractionation Fractional extraction Fractionation, seeDistillation Free-volume theory of diffusion Freezing-point determination Fugacity of nitrogen standard state Fugacity coefficient composition dependence of acetic acid vapor... 

Fig. 16.4. Solubility of liquid decane in nitrogen gas at 50°C, calculated from Henry s Law coefficient and decane fugacities based on ideal gas and Lewis Fugacity Rule approximations and the virial equation. Experimental data are solid dots. After Prausnitz (1969)...

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