Calculation from partial pressure

Since in most cases the equation of state for a mixture is not known, it is assumed as a rule that the fugacity of a component in a mixture can be calculated from partial pressure or partial vapour pressure just in the same way as if the component existed in pure form at this pressure. By this method the effect of the nonidead behaviour of the vapour on the equihbrium can be determined. 

An equation for calculating the partial pressure of chlorine dioxide above specified chlorine dioxide solutions at various temperatures based on the data from reference 24 has been developed (25) ... 

Strategy, we calculate the partial pressure of oxygen p(O2) from Dalton s law (see p. 221), saying p(02) = total pressure of the air x mole fraction of oxygen in the air. Substituting values into the above equation ... 

From the total pressure at each time interval, calculate the partial pressures of NO and 02 that must remain. From the information in the problem, you can see that in Series = 100 - 2(AP), and in series (2) Po2 = 20.0 - AP. By using the ideal... 

Worked Examples 13.9 and 13.10. The same approach can be used to calculate equilibrium partial pressures from initial partial pressures and Kp, as shown in Worked Example 13.11. 

A unimolecular decomposition - calculation of observed first order plots from partial pressure with time data, and illustration of the falling off in the first order rate constant with decrease in pressure, 146-147... 

Because the total pressure is unknown, it is simplest to calculate the partial pressure directly from Dalton s law (Chapter 5). 

We calculate the partial pressure of water from the relative humidity and the... 

From a similar graph4 it is possible to calculate the partial pressure of nitrogen pentoxide, n2o6> at any time knowing the total pressure and the initial pressure. The pressure increase, P total — pi, 4 Details are given in J. Am. Chem. Soc., 43, 53 (1921). 

The enthalpy of formation, AjH (WClg, cr, 298.15 K) -122.6 kcal mol , is calculated from that of the gas less the heat of sublimation, Ag H (298.15 K) 24.0 kcal mol . The latter is calculated by the 3rd law method from partial pressures of WClg(g) derived from the total pressure data of Shchukarev et al. (1 ). Dimer pressures, calculated from the same authors dimer-monomer dissociation data, are subtracted from the total pressures in order to obtain the monomer pressures. Analyses of... 

These equations enable us to calculate the partial pressures and P2> hence also the activity coefficients, when we know the total pressure as a function of mole fraction. This is an extremely interesting possibility since, from the point of view of experimental technique it is much easier to determine total pressures than partial pressures. 

The calculation of partial pressures from total pressure curves is the subject of papers by Stein and Voetter,f Kohler,] Nowotny and Orlicek, and by Barker. ... 

The partial pressures of gases at the same temperature are related to their concentration. The partial pressure of water vapor has a fixed value at a given temperature. You can look up the value in a reference table. At 20°C, the partial pressure of water vapor is 2.3 kPa. You can calculate the partial pressure of hydrogen by subtracting the partial pressure of water vapor from the total pressure. If the total pressure of the hydrogen and water mixture is 95.0 kPa, what is the partial pressure of hydrogen at 20°C ... 

Henry s law is important in environmental chemistry, where it predicts the distribution of pollutants between water and the atmosphere. Benzene (CgHg) emitted in wastewater streams, for example, can pass into the aii where it is degraded by processes induced by light from the sun. The Henry s law constant for benzene in water at 25°C is 301 atm. Calculate the partial pressure of benzene vapor in equilibrium with a solution of 2.0 g of benzene per 1000 L of water. How many benzene molecules are present in each cubic centimeter ... 

EXAMPLE 3.9 Calculation of Partial Pressures from Gas Analysis... 

The vapor pressure of water at 94°F is 1.61 in. Hg. We can calculate the partial pressure of the water vapor in the air from the given percent relative humidity from this point forward, the problem is the same as the examples in Section 3.4. 

Initially, the vapor pressure measurements appear to be the most direct, but even here some assumptions are needed. The amount of alcohol in the micellar phase needs to be determined. To do this the difference in vapor pressure between a pure aqueous and a micellar solution is measured. If the ions of the surfactant salts out alcohol, the vapor pressure of pure water is not the correct comparison, and this could lead to lower partition coefficients. Thermodynamic data are well suited for model calculations, and both the models of DeLisi et al. ° ° and Hetu et al. fit the data well. Although in reasonable internal agreement, the partition coefficients calculated from partial molar volumes differ from those calculated from enthalpies the first is 927 or 944, the latter... 

Its principle of operation is based on Boyle s Law, in that a fixed large volume of the gas at the unknown pressure is compressed to a fixed small volume. The pressure of the gas following compression is measured by a mercury manometer, and the initial pressure is calculated from this pressure and the volume ratio. Pressures as low as 10-6 mm. Hg can be accurately measured by this gage. A major cause for error is the presence of condensable vapors in the gas being measured. Under such conditions the pressure obtained with this gage is closer to the partial pressure of noncondensables than the total pressure. It is not exactly equal to the partial pressure of noncondensables, however, because the condensable vapors may exert a significant vapor pressure after condensation. 

From mole fractions and total pressure, we can calculate the partial pressures of individual components, as Example 5.15 shows. A direct application of Dalton s law of partial pressures to scuba diving is discussed in the Chemistry in Action essay on p. 179. 

Ask your instructor what a normal atmospheric pressure is for your area, measure it if you have a barometer in the laboratory, or get it from the local weather station, and then calculate the partial pressures of each component and the expected boiling point of the mixture. 

Table II. Henry s Law Constants (Kh and K h) from 0 - 40°C. Values at 25°C determined from partial pressure data. Estimates calculated from available free energy data (22) are also shown. Temperature dependence (T/Kelvin) given by ln(KH, K h) = a + b/T + cT Part 1 Kh (HX(g) = H+(aq) + X (aq)) ...

Figure 1. The quotient mCH3COOH/pCH3COOH calculated using partial pressure data from the following sources dots - Fredenhagen and Liebster (2S) triangles - Kaye and Parks (29) squares -Campbell et al. QI) open diamonds - Zarakhani and Vorob eva (57V. closed diamond - Wolfenden...

When calculating gas partial pressures it quickly becomes apparent that the principal temperature effect lies in the change of Kh rather than in the activity coefficients. In Equation 9 a constant 5C°p for the solubility equilibrium is assumed. While this is unlikely to result in appreciable errors over the temperature range 0-40°C, further from 25°C the variation of 6C°p has a significant effect on Kh, requiring a more complex form of Equation 9 (55). However, the necessary data are not always available, particularly for C°p of the aqueous solute which generally accounts for most of the change. 

First, MINTEQ was used to calculate the partial pressure of CO2 gas in equilibrium with the two fluids listed in Tkble III. Based upon measured alkalinity and pH, the raw L2 leachate (point 1, Figure 2) was computed to have a CO2 pressure of 1(> atmosphere. After 5-day reaction with the Uinta Sandstone (point 4, Figure 2), the measured pH and alkalinity of the fluid yielded a calculated CO2 pressure of 1(> atmosphere. Leachate recarbonation was simulated by fixing the CO2 gas partial pressure of the unreacted fluid in the absence of sandstone at the theoretical value of atmosphere (point 2, Figure 2), and in the presence of sandstone at the value of 1(> atmosphere calculated from leachate chemistiy (point 3, Figure 2). It is assumed that, when open to the atmosphere, the system will ultimately approach equilibrium with ambient CO2 pressure (in Boulder) of 10 atmosphere (point 5, Figure 2). 

In the processing of polymers, and also for polyrfier devolatilization (the removal of the solvent from the polymer), it is important to be able to calculate the equilibrium partial pressure of a solvent above solvent-polymer mixtures of different compositions. Calculate the partial pressure of benzene in benzene + polyisobutylene (PIB) mixtures at 298.15 and 312.75 K. In this calculation you can assume that polyisobutylene has a negligible vapor pressure, and that the Floty-Huggins model describes the solution behavior of this polymer + solvent mixture. Do the calculations fdr values of the Flory-Huggins y parameter equal to 0.5 to 1.0. 

To calculate the amount of steam in the product gases, the total input water is adjusted for the amount consumed in the shift reaction and for the water produced from oxygen in the coal to calculate the partial pressure of steam and other gases, the volume of the product gases is taken as the average of the input gas volume and the corrected output gas volume. The amount of CO2 remaining in the catchpot liquids is... 

Assuming that each gas behaves ideally, we can calculate the partial pressure of each gas from the ideal gas law ... 

Strategy To solve for moles of H2 generated, we must first calculate the partial pressure of H2 in the mixture. What gas law do we need How do we convert from moles of H2 to amount of Zn reacted ... 

The rate constant, k, is given. If the concentrations of CH3 and C2H6 can be determined, the initial rate of the reaction can be calculated. The partial pressures of CH3 and C2H6 can be calculated from the respective mole fractions and the total pressure. Once the partial pressures are known, the molar concentrations can be calculated using the ideal gas equation. 

We can now calculate the partial pressure of NO2 from the mole fraction and the total pressure. 

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