Dinitrogen tetroxide, equilibrium with

In sulphuric acid, nitrous acid has a catalytic effect since dinitrogen tetroxide reacts with sulphuric acid to give nitronium ions according to equilibrium (39)102. 

The photochemical reaction of Re2(CO)io with PMePhg seems to fit into this two-equilibrium scheme fairly well, and so represents a recently discovered example of substitution at M2(CO)io without metal-metal bond cleavage. Dinitrogen tetroxide reacts with Re2(CO)io to cleave the metal-metal bond and give ultimately Re(N03)(C0)5, by the following sequence ... 

Since the first-order rate constant for nitration is proportional to y, the equilibrium concentration of nitronium ion, the above equations show the way in which the rate constant will vary with x, the stoichiometric concentration of dinitrogen tetroxide, in the two media. An adequate fit between theory and experiment was thus obtained. A significant feature of this analysis is that the weak anticatalysis in pure nitric acid, and the substantially stronger anticatalysis in partly aqueous nitric acid, do not require separate interpretations, as have been given for the similar observations concerning nitration in organic solvents. 

Nitrogen dioxide forms an equilibrium with dinitrogen tetroxide. When it is cold, the equilibrium favours the second compound. Depending on the thermal conditions, the dangerous reactions will involve one or the other of these two compounds. Their endothermic character makes them hardly stable. 

Nitrogen dioxide rapidly forms an equilibrium mixture with its dimer, dinitrogen tetroxide or nitrogen peroxide [see Eq. (9.11)]. The formation of the tetroxide is favored by low temperature and high pressure104. 

The prediction made with Le Chatelier s principle is purely quali tative—it states only that some of the dinitrogen tetroxide would decompose. However, we could make use of the equilibrium equation above, to calculate exactly how much of the dinitrogen tetroxide would decompose. This calculation will be made in a following paragraph. 

Heat of Reaction and the Tendency of the Reaction to Take Place. It has been pointed out in earlier paragraphs tiiat some reactions tliat take place are exothermic, and some are endothermic. A reacti()n that reaches a measurable equilibrium may be caused to go in either direction, by starting with one set of reactants or another. For example, the reaction involving tiie red gas nitrogen dioxide and the colorless gas dinitrogen tetroxide has a heat effect shown by the following equation ... 

And it exists in equilibrium with its colorless dimer, dinitrogen tetroxide ... 

At 100°C this equilibrium lies at approximately 90% NOi, 10% N2O4, whereas at 21°C only about 0.1% NO2 is present [41]. This equilibrium may be important for acid production since there is evidence that dinitrogen tetroxide is the molecular species that reacts with water for acid formation. 

However WFNA is relatively unstable and with time develops a certain amount of dinitrogen tetroxide. More stable for rocket propulsion is red fuming nitric acid (RFNA) which contains cc. 14 wt% N2O4. It is formed from WFNA or from nitric acid with added N2O4. RFNA is the equilibrium product formed from both extremes of the concentration range ... 

Dinitrogen tetroxide (N2O4), which is in equilibrium with nitrogen dioxide. 

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. 

P12.6 The dissociative gas and important rocket propellant dinitrogen tetroxide is in rapid equilibrium with nitrogen dioxide following the reaction ... 

The reversible reaction between dinitrogen tetroxide (N2O4) and nitrogen dioxide (NO2), depicted with space-filling models in Figure 10.1, is an example of a chemical equilibrium. The progress of the reaction... 

Nitrogen dioxide, NO2, a red gas, and its dimer dinitrogen tetroxide, N2O4, a colorless, easily condensable gas, exist in equilibrium with one another ... 

It is paiamagnetic, and its free>radical character predisposes it to combine with itself to produce the lighter-colored dinitrogen tetroxide. The two gases exist in equilibrium at ordinary temperatures (page 127) ... 

The nitric oxide which is formed reacts with oxygen to form nitrogen dioxide. Nitrogen dioxide exists in equilibrium with its dimer, dinitrogen tetroxide. The nitrogen dioxide/dimer mixture is sent to a column, sometimes called an absorption tower. Water is added at the top of the column. The nitrogen dioxide is converted to nitric acid. Byproduct nitric oxide is oxidized to nitrogen dioxide by means of a stream of air passed into the absorption column. The aqueous nitric acid is removed continuously from the base of the column. Overall, the reaction can be written as ... 

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