Nitrogen dioxide equilibrium pressure

The quantity K is called the equilibrium constant of the reaction of dissociation of dinitrogen tetroxide to nitrogen dioxide. The equilibrium constant is independent of the pressure of the system, or of the concentration of the reacting substances. It is, however, a function of the temperature. 

In some cases it has been found possible to determine the rates of the opposing reactions, and to show experimentally that the ratio of the two rate constants is indeed equal to the equilibrium constant. This has not been done for the nitrogen dioxide-dinitrogen tetroxide equilibrium, however, because the individual chemical reactions take place so rapidly that expetimenters have not been able to determine their rates. It has, indeed, been found by experiment that if the pressure... 

For a process absorber which does not normally operate very close to equilibrium, the rate of the reverse reaction (the second term in this rate equation) can be ignored. The pressure increase also boosts the rate of nitrogen dioxide absorption, once formed, in water. In practice this pressure increase means... 

It is conventional to imagine these processes that destroy and produce nitrogen dioxide (N02) as in a kind of equilibrium, which is represented by a notional equilibrium constant relating the partial pressures of the two nitrogen oxides and 03 ... 

The formation of the nitrogen oxides, nitric oxide (NO) and nitrogen dioxide (NO2) from N2 and O2, provides an example of the interplay between thermodynamics and kinetics. The calculation of the equilibrium concentrations of NO and NO2 is straightforward if we assume that these are the only compounds formed and that the initial pressures of N2 and O2 are known. 

Nitrogen dioxide (N02) dimerizes almost instantaneously to an equilibrium mixture of N02 and N204 as shown in Reaction 3.13. This reaction is also favored at lower temperatures and increasing pressures. 

A mixture of nitrogen dioxide and dinitrogen tetroxide are allowed to come to equilibrium at 30 °C, and their partial pressures are found to be 1.69 atm N2O4 and 0.60 atm NO2. 

The study of physical equilibrium yields useful information, such as the equilibrium vapor pressure (see Section 11.8). However, chemists are particularly interested in chemical equilibrium processes, such as the reversible reaction involving nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4) (Figure 14.1). The progress of the reaction... 

The extent of reaction X and the mole fraction of nitrogen dioxide as a function of temperature and pressure are plotted in Fig. 2. (Note that the equilibrium constant is independent of pressure, but the equilibrium activity ratio increases linearly with pressure. Therefore, the extent of reaction for this reaction decreases as the pressure increases.)... 

PHYSICAL PROPERTIES yellowish-brown liquid or reddish-brown gas (above 70°F) in solid form (below 15°F) may appear as white to bluish-white snow pungent, irritating odor soluble in concentrated sulfuric acid and nitric acids soluble in alkalies, chloroform, and carbon disulfide commercial brown liquid under pressure is an equilibrium mixture of nitrogen dioxide and the colorless N2O4 MP (-9°C, 15°F) BP (21°C, 70°F) DN (1.448 g/mL liquid at 20°C) LSG (1.44 at 68°F) HV (9.110 kcal/mol) VD (1.58) VP (400 mmHg at 80 C) OT (4 ppm). 

SOLID-VAPOR EQUILIBRIUM OF THE CARBON DIOXIDE-NITROGEN SYSTEM AT PRESSURES TO 200 ATMOSPHERES... 

The first coefficient describes the most common case, namely how much entropy AS flows in if the temperature outside and (also inside as a result of entropy flowing in) is raised by AT and the pressure p and extent of the reaction are kept constant. In the case of the secmid coefficient, volume is maintained instead of pressure (this only works well if there is a gas in the system). In the case of J = 0, the third coefficient characterizes the increase of entropy during equilibrium, for example when heating nitrogen dioxide (NO2) (see also Experiment 9.3) or acetic acid vapor (CH3COOH) (both are gases where a portion of the molecules are dimers). Multiplied by T, the coefficients represent heat capacities (the isobaric Cp at constant pressure, the isochoric Cy at constant volume, etc.). It is customary to relate the coefficients to the size of the system, possibly the mass or the amount of substance. The corresponding values are then presented in tables. In the case above, they would be tabulated as specific (mass related) or molar (related to amount of substance) heat capacities. The qualifier isobaric and the index p will... 

Absorber performance is controlled by temperature and pressure. At reduced temperatures the gas-phase equilibrium moves toward the formation of dinitrogen tetroxide and an increased solubility in HNO3. Therefore, lower temperatures improve the absorption rate and increase the acid concentration. At higher pressures the NO oxidation reaction is quicker, and equilibrium moves toward nitrogen dioxide. In addition, with higher pressure more concentrated nitric acid is produced. 

Nitrogen dioxide decomposes according to the reaction 2N02(g) 2NO(g) + 02(g) where Kp = 4.48X 10 at a certain temperature. A pressure of 0.75 atm of NO2 is introduced into a container and allowed to come to equilibrium. What are the equilibrium partial pressures I ofNO(g) and 02(g) ... 

The mixture is a pungent brownish liquid that boils at 2UC. Lower temperatures and increasing pressure shift the reaction to the production of nitrogen tetroxide. Nitrogen dioxide is a brown paramagnetic species while the dimer is colorless and diamagnetic at 21°C the equilibrium mixture contains 0.08% NOg. 

A decrease in pressure will favour the decomposition to nitrogen dioxide, NOj, as this side of the reaction occupies a greater volume. The equilibrium will shift to the right, the direction of the expansion in volume. 

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