Equilibrium oxygen pressure

In the case of tire direct oxidation, the oxygen partial pressure must be greater than that at the Pb/PbO equilibrium, while in the process involving sodium-based salts, the oxygen pressure is less than this. The two equilibrium constants for the refining reactions... 

Vapor pressures and vapor compositions in equilibrium with a hypostoichiometric plutonium dioxide condensed phase have been calculated for the temperature range 1500 I H 4000 K. Thermodynamic functions for the condensed phase and for each of the gaseous species were combined with an oxygen-potential model, which we extended from the solid into the liquid region to obtain the partial pressures of O2, 0, Pu, PuO and Pu02 as functions of temperature and of condensed phase composition. The calculated oxygen pressures increase rapidly as stoichiometry is approached. At least part of this increase is a consequence of the exclusion of Pu +... 

The temperature dependences of the total pressures In equilibrium with the condensed-phase composition PuOj gQ, PuOl.96> and P11O1.994 are compared in Figure 4. The differences shown In Figure 4 are due to the differences In oxygen pressures for the different compositions. 

It appears that the presence of U6+, for which there is no counterpart in the Pu/O system, is responsible for preventing the oxygen pressures from increasing as rapidly in the mixed-oxide system as in the plutonia system. These results (39J indicate that the oxygen partial pressures in equilibrium with the mixed oxide will not differ drastically from those in equilibrium with urania. 

Measurement of the equilibrium oxygen pressure as functions of both x and T at higher temperatures than are currently available. 

Fig. 1.20. The dependence of equilibrium electric conductivity of ZnO sample on oxygen pressure...

Fig. 1.21. The dependence of equilibrium value of the tangent of inclination angle of pre-relaxation VAC on oxygen pressure (/ - oj)=11.8 nA/V 2-ao = 2.25 pA/V)...

In the system iron/oxygen (C = 2), when two phases are present, e.g. Fe304 and oxygen, pressure and temperature can be varied (F = 2). When three phases are in equilibrium, e.g. Fe, Fe203 and Fe304, only one degree of freedom exists, and only the pressure or the temperature can be chosen freely. 

A conductivity cell is set up using an yttria-stabilized zirconia electrolyte. At 900°C the equilibrium pressure in the cell was 1.02 x 10-10 atm, and the reference pressure outside the cell was 7.94 x 10 18 atm. (a) What is the cell voltage The temperature was dropped to 800°C and the reference pressure changed to 1.61 x 10-19 atm. The measured equilibrium voltage was 946 mV. (b) What is the equilibrium oxygen pressure in the cell [Data adapted from D-K. Lee et al., J. Solid State Chem., 178, 185-193 (2005).]... 

At a fixed temperature, AGr is constant, and so the equilibrium oxygen partial pressure, po2, will also be constant. This oxygen pressure is called the decomposition pressure or dissociation pressure of the oxide and depends only upon the temperature of the system. 

What does this imply Suppose some silver metal and silver oxide is sealed in a closed silica ampoule, under a complete vacuum, and the ampoule is heated to a temperature somewhat below the decomposition temperature of 230°C. As there is no oxygen in the ampoule, some of the silver oxide will decompose and oxygen will be released. This will continue until the equilibrium decomposition pressure is reached. Provided that there is both silver and silver oxide in the tube, the oxygen pressure will be fixed (Fig. 7.5a). If the temperature is raised or lowered, either more silver... 

The equilibrium oxygen pressure over the series of iron oxides at 1100°C is shown in the figure, (a) What phases are involved (b) What does the sloping part of the plot indicate (c) Write equations for each of the formation reactions taking place, (d) Estimate the value of the reaction Gibbs energy, AGr per mole of product, at 1100°C for each reaction. The value of AGr for the formation of... 

One of the steps in the leaching and purification of zinc electrolyte is the oxidation of ferrous to ferric iron, with the subsequent precipitation of Fe(0H)3. Calculations (5 ) may be performed to determine the influence of pH and oxygen pressure on the final equilibrium ratio obtained for these two ions. 

Figure 2.33. Ni-Co-O phase diagram (isothermal section at 1600 K). log p02 (oxygen partial pressure) is plotted against the molar fraction in the metallic alloy. The metallic alloy, (Ni, Co) solid solution is stable in (1) and the mixed oxide (Ni, Co)0 solid solution in (3). In the intermediate region (2) we have coexistence of alloy and oxide. For the value of the partial oxygen pressure corresponding to y, within the two-phase field, we will have the alloy of composition xt in equilibrium with an oxide containing the two metals in the ratio x2-...

If one assumes that the reaction system is at thermodynamic equilibrium, the oxygen electrode method also allows one to infer the partial pressure of oxygen in equilibrium with the test solution. 

As Equation 1 indicates, adding water would decrease the concentration of carbanions by shifting the equilibrium to the left. Experimentally, the ratio of anthraquinone to anthracene was 2.6 to 1 in anhydrous pyridine with oxygen at 1 atm., but was increased to 7.2 to 1 in 95 volume % aqueous pyridine. Further addition of water to 10% decreased the over-all reaction rate. Water had no effect at higher oxygen concentrations (oxygen pressure of 4 atm.). 

Oxidation of zinc to zinc oxide is another example whose kinetics have been interpreted in terms of the Wagner model (Wagner Grunewald, 1938). At 670 K, the reaction has been found to be independent of oxygen pressure between 0.02 and 1 atm. ZnO is a n-type semiconductor, having a stoichiometric excess of zinc accommodated as interstitials the defect equilibrium could be represented as... 

Oxygen adsorption has also been studied on zinc oxide, an n-type oxide, by Wagner (63) and later by Bevan and Anderson (64). The conductivity decreases with increase in oxygen pressure, a result interpreted by Wagner by assuming the equilibrium... 

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