Partial pressures defined

Dalton s law of partial pressures The total pressure (P) exerted by a mixture of gases is equal to the sum of the partial pressures (p) of the components of the gas mixture. The partial pressure is defined as the pressure the gas would exert if it was contained in the same volume as that occupied by the mixture. 

As pointed out in Volume 1, the fraction of any one component that flashes to gas at any stage in a process is a function of the temperature, pressure, and composition of the fluid at that stage. For a given temperature this tendency to flash can be visualized by the partial pressure of the component in the gas phase that is in equilibrium with the liquid. Partial pressure is defined as ... 

For gas mixtures, the partial pressure is defined as the pressure that would be exerted if that component alone occupied the volume of the mixture. Thus, for an ideal gas,... 

The smallest detectable partial pressure is defined as a ratio of noise amplitude to sensitivity ... 

The partial derivative of the Gibbs free energy per unit area at constant temperature and pressure is defined as the interfacial coefficient of the free energy or the interfacial tension (y), a key concept in surface and interface science ... 

Partial pressure — Symbol ps, defined as ps = ysp (ys mole fraction of B, p total pressure). Partial pressure and -> fugacity are sometimes used as concentrationlike measures for gaseous compounds, e.g., in case of gas electrodes. 

The partial pressure is defined as the total pressure times the mole fraction of the component in the vapor phase. Therefore ... 

The Vapor Pressure of Liquids. Vapor pressure is defined as the pressure exerted by a vapor in equilibrium with its liquid. Consider a closed, evacuated container which has been partially filled with a liquid. The molecules of the liquid are in constant motion but not all the molecules move with the same velocity and there will be some which possess a relatively high kinetic energy. If one of these fast moving molecules reaches the liquid surface, it may possess sufficient energy to overcome the attractive forces in the liquid and pass into tiie vapor space above. As the number of molecules in the vapor phase increases the rate of return to the liquid phase also increases and eventually a condition of dynamic equilibrium is attained when the number of molecules leaving the liquid is equal to the number returning. The molecules in the vapor phase obviously exert a pressure on the containing vessel and this pressure is known as the vapor pressure. 

So the fractional gas concentrations in the fluid at any time can be determined solely by integrating the output curve during depletion. The output of the mass spectrometer is a function of the partial pressure in the fluid. Therefore, it is possible to obtain continuously the relationship between the concentration and partial pressure. This defines the solubility curve. 

Henry s law is valid only at low concentrations of B. Since partial pressure is defined as... 

From what we have seen so far, you may have the impression that the molar mass of a substance is found by examining its formula and summing the molar masses of its component atoms. However, this procedure works only if the actual formula of the substance is known. In practice, chemists often deal with substances of unknown or only partially defined composition. If the unknown substance is gaseous, its molar mass can nevertheless be found thanks to the ideal gas equation. All that is needed is an experimentally determined density value (or mass and volume data) for the gas at a known temperature and pressure. By rearranging Equation (5.11) we get... 

A five-point, second-order correct operator is defined for the pressure partial for each phase q as... 

Let us now separate the two gases into individual containers,each having the original volume. The pressures exerted in the new containers are called the PARTIAL PRESSURES, Pi and p. The partial pressure is defined simply as the pressure that one component of a gas mixture would exert if it occupied the same volume alone. Then,... 

For Dalton s law partial pressure is defined as the pressure that would be exerted by a component alone at the same molal concentration that it has in the mixture. If the perfect-gas laws apply to each of the components individually and to the mixture, it can be shown that the partial pressure of any component is equal to the mol fraction times the total pressure,... 

I artial pressure was defined by Eq. (12.1). With regard to humidification, the liquid is essentially pure, so x in Eq. (12.2) is 1.0. At equilibrium (100 percent saturation), the partial pressure of water vapor is equal to its vapor pressure at the prevailing temperature, that is, Pu, = P -... 

Homogeneous liquid in a uniform radial flow. Now we repeat the same calculation for cylindrical radial flows. The pressure partial differential equation governing transient, compressible, radial, homogeneous, liquid flows having constant properties is 5 p(r,t)/5r + (Ur) 5p/5r = (< )pc/k) 5p/5t. All of our quantities are defined as in the lineal flow, except that the radial coordinate r replaces the lineal coordinate x. If we assume an incompressible fluid with vanishing c, we obtain the differential equation d p(r)/di + (1/r) dp/dr = 0, whose solution is p(r) = A log r -I- B. For this radial flow, we impose pressure boundary conditions at the well and outer reservoir radii (that is, at and r j) in Figure 17-2, in the form = Pweii and p(rres) = Pres- We emphasize that... 

For a pure gas the partial pressure is equal to the total pressure (because y, = 1.0 for a pure gas). For any gas mixture the sum of the partial pressures equals the total pressure, = PJlyi = P because the sum of the mol fractions is unity. The partial pressure is defined only for gases this term is not used for solids and liquids. 

We regularly use y,-, for mol fractions in the gas phase and x,-for mol fractions in the liquid phase, P for the total pressure of the gas and pi for the pure-species vapor pressure of species i in the liquid.) For a pure liquid the partial vapor pressure is equal to the pure liquid s vapor pressure at that temperature (because x, = 1.0 for a pure liquid). For one kind of ideal solution (defined in Chapter 7) the sum of the partial vapor pressures equals the total vapor pressure of the liquid. The partial vapor pressure is defined only for liquids it is occasionally used for solids and never for gases. 

Nonreacting Ideal Gas Mixture Calculation In many cases relevant to fuel cells, we must deal with mixtures rather than pure gases. Thermodynamic properties of mixtures can be easily calculated based on the mole or mass fractions of the constituents. A good example of this is air, which is a nonreacting mixture of mostly nitrogen and oxygen. For these mixtures, we can assume each species in the mixture is occupying the total volume but at a partial pressure in the mixture, where the partial pressure is defined as... 

For gas reactions where the gases are assumed to follow ideal behaviour this equation becomes AG° = RT]n Kp, where Kp is defined in terms of the partial pressures of reactants and products. Thus for the general reaction above,... 

Influence of added substances upon the critical solution temperature. For a given pressure the C.S.T. is a perfectly defined point. It is, however, affected to a very marked extent by the addition of quite a small quantity of a foreign substance (impurity), which dissolves either in one or both of the partially miscible liquids. The determination of the consolute temperature may therefore be used for testing the purity of liquids. The upper consolute temperature is generally employed for this purpose. 

The first term, AG°, is the change in Gibb s free energy under standard-state conditions defined as a temperature of 298 K, all gases with partial pressures of 1 atm, all solids and liquids pure, and all solutes present with 1 M concentrations. The second term, which includes the reaction quotient, Q, accounts for nonstandard-state pressures or concentrations. Eor reaction 6.1 the reaction quotient is... 

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