N2O5, decomposition

It appears then that, although the last word on this subject is far from being said, the N2O5 decomposition is one of the best understood of our complex reactions, and the mechanism for it is probably as well founded as any of the kinetic mechanisms that have been presented up until now. 

It is to be noted that the order of a reaction cannot be predicted from the stoichiometric over-all equation. The equation for the N2O5 decomposition makes use of two molecules of the reactant, but the reaction is in fact a first-order reaction. This shows that the reaction takes place in steps first there occurs a first-order decomposition, probably... 

The nitrations of benzene and nitrobenzene by dinitrogen pentaoxide in carbon tetrachloride have been studied. It was concluded that dinitrobenzenes could be formed directly from benzene without the intermediacy of nitrobenzene. It was suggested that the initially attacking species is NOs and that dinitrobenzenes could be formed by the reaction of the intermediate formed by such attack reacting with NO2, formed by N2O5 decomposition above 25 °C. The reactions of 2-nitrotoluene, l-chloro-2-nitrobenzene, and l-chloro-4-nitrobenzene with dinitrogen pentaoxide in dichloromethane at 0°C are catalysed by certain zeolites giving near quantitative yields. In this process the activated site on the zeolite may provide an incipient nitronium ion for reaction. 

As we will see shortly, the rate expression can take various forms, depending on the nature of the reaction. It can be quite simple, as in the N2O5 decomposition, or exceedingly complex. 

This change results in a break in the Arrhenius line. This is what we have already seen in the example of N2O5 decomposition (see section 7.4.2) and in the catalysis example (section 7.4.5 and Figure 7.7), in which the resulting two extreme cases were the two modes with a single determining step. 

A plot of rate versus concentration for the decomposition of N2O5 is a straight line. The... 

Many reactions that take place in a solvent do not occur in the gas phase. This statement is generally true for ionic reactions. Homolytic decompositions of neutral molecules can sometimes be observed in both. One reaction that can be studied in the gas phase and in a variety of solvents is the decomposition of N2O5,... 

Dinitrogen pentoxide, N2Os, decomposes by first-order kinetics with a rate constant of 0.15 s 1 at 353 K. (a) What is the half-life (in seconds) for the decomposition of N2Os at 353 K (b) If [N2O5]0 = 0.0567 mol-L, what will be the concentration of N2Os after 2.0 s (c) How much time (in minutes) will elapse before the N205 concentration decreases from 0.0567 mol-L 1 to 0.0135 mol-L ... 

What is the order of the decomposition reaction (which for this purpose can be written as N2O5 - N2O4 + 5O2) Assume the reaction goes to completion. 

Rate constants for the first-order decomposition of nitrogen pentoxide (N2O5) at various temperatures are as follows (Alberty and Silbey, 1992, p. 635) ... 

The decomposition of N2O5 in the gas phase to N2O4 and O2 is complicated by the subsequent decomposition of N2O4 to NO2 (presence indicated by brown color) in a rapidly established equilibrium. The reacting system can then be modeled by the kinetics scheme... 

From the coefficients in the balanced chemical equation, you can see that the rate of decomposition of N2O5 is or -, the rate of formation of... 

A first-order reaction has an overall order of 1. The decomposition of dinitrogen pentoxide, N2O5, is an example of a first-order reaction. 

This graph shows [N2O5] versus time for the first three half-lives of the decomposition reaction of N2O5 at 44°C. The spheres in the cubes represent [ N2O5]. 

B) In examining the balanced equation, note that for each mole of N2O5 gas that decomposes, Vi mole of O2 gas is formed. Therefore, the rate of formation of oxygen gas should be half the rate of decomposition of the N2O5. 

Let us examine the decomposition reaction of dinitrogen pentoxide, N2O5, at 30°C. N205(g) 2N02(g) + 1/202(9)... 

The following mechanism has been proposed for the decomposition of N2O5 ... 

The reaction rate can be defined either as the increase in the concentration of a product per unit time or as the decrease in the concentration of a reactant per unit time. Let s look first at product formation. In the decomposition of N2O5, the rate of formation of O2 is given by the equation... 

Initial rate data for the decomposition of gaseous N2O5 at 55°C are as follows ... 

Experimental concentration-versus-time data for the decomposition of gaseous N2O5 at 55°C are listed in Table 12.1 and are plotted in Figure 12.1. Use those data to confirm that the decomposition of N2O5 is a first-order reaction. What is the value of the rate constant for consumption of N2O5 ... 

Because the decomposition of N2O5 is a first-order reaction (Worked Example 12.6), we can determine its half-life either from the time required for [N2O5] to drop to one-half of its initial value or from the equation fj/2 = 0.693/k. To find [N2O5] after n half-lives, multiply its initial concentration by (1/2)" since [N2O5] drops by a factor of 2 during each successive half-life. 

Decomposition of N2O5 is a first-order reaction. At 25°C, it takes 5.2 h for the concentration to drop from 0.120 M to 0.060 M. How many hours does it take for... 

Another classic example of a complex reaction is the decomposition of N2O5 which shows first order kinetics, but with the first order rate constant decreasing in value as the pressure is lowered. Superficially, this could be taken as evidence of a typical unimolecular decomposition. However, even a first glance at the stoichiometry of the reaction should suggest that it is unlikely that there is a simple one step breakdown of N2O5 into the products. 

Product studies on DMSO/N2Q5 mixtures were performed in 760 Torr of synthetic air. HNO3 and DMSO were the only observed products. HNO3 can be accounted for entirely by the HNO3 entering the reactor with the NzO5 and also by the decomposition of N2O5 at the reactor surface. It could, however, also be formed by tne abstraction reaction (11),... 

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