Oxides and Oxyacids of Nitrogen

Nitrogen forms three common oxides N2O (nitrous oxide), NO (nitric oxide), and NO2 (nitrogen dioxide). It also forms two unstable oxides that we will not discuss, N2O3 (dinitrogen trioxide) and N2O5 (dinitrogen pentoxide). 

Nitrous oxide (N2O) is also known as laughing gas because a person becomes giddy after inhaling a small amount. This colorless gas was the first substance used as a general anesthetic. It is used as the compressed gas propellant in several aerosols and foams, such as in whipped cream. It can be prepared in the laboratory by carefully heating ammonium nitrate to about 200 °C  

Nitric oxide (NO) is also a colorless gas but, unlike N2O, it is slightly toxic. It can be prepared in the laboratory by reduction of dilute nitric acid, using copper or iron as a reducing agent (T FIGURE 22.24)  

Nitric oxide is also produced by direct reaction of N2 and O2 at high temperatures. This reaction is a significant source of nitrogen oxide air pollutants. (Section 18.2) The direct combination of N2 and O2 is not used for commercial production of NO, however, because the yield is low, the equilibrium constant Kp at 2400 K being only 0.05. (Section 15.7, Chemistry Put to Work Controlling Nitric Oxide Emissions ) 

The commercial route to NO (and hence to other oxygen-containing compounds of nitrogen) is via the catalytic oxidation of NH3  

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The numerous oxides and oxyacids of sulfur which are known are listed in the accompanying table I together with the nitrogen analogs which have been found up to the present R denotes an organic radical and Me a metal atom. 

Schwartz SE, White WH. Solubility equilibria of the nitrogen oxides and oxyacids in dilute aqueous solutions. In Pfafflin JR, Zeigler EN, eds. Advances in Environmental Science and Engineering. Vol. 4. New York Gordon and Breach, 1981 1 45. 

S. E. Schwartz, W. H. White, Solubility Equilibria of the Nitrogen Oxides and Oxyacids in Dilute Aqueous Solutions, in Advances in Environmental Science and Engineering, J. R. Pfafflin and E. N. Zeigler (Eds.), Gordon and Breach Science Publ., New York, 1981. 

The discussion that follows first describes techniques for the airborne collection of a definable atmospheric phase for subsequent determinations, then continues with discussion of the analysis techniques themselves including those for nitrogen oxides and oxyacids, sulfur oxides, oxidants and selected organic species. Emphasis is on the modified instrumentation devised and used by Brookhaven National Laboratory staff to improve the selectivity and lower the limits of detection of these techniques (1). 

Nitrogen Hydrides Nitrogen Oxides Oxyacids of Nitrogen 20.9 The Chemistry of Phosphorus Phosphorus Oxides and Oxyacids... 

The two common oxyacids of nitrogen are nitric acid (HNO3) and nitrous acid (HNO2) ( FIGURE 22.26). Nitric acid is a strong acid. It is also a powerful oxidizing agent, as indicated by the standard reduction potential in the reaction... 

Among the oxygen group elements, while sulfur is oxidized to +6 oxidation state (in H2SO4), selenium and tellurium are oxidized to +4 oxyacids with the liberation of nitrogen dioxide ... 

Nitrous and nitric acids are produced in the aqueous phase after NO2 and/or N2O3 are absorbed into solution and sulfur oxyacids, such as sulfite/bisulfite or pyrosulfite, are formed if SO2 dissolves in the solution. Interaction among oxides of nitrogen, nitrogen oxyacids, sulfur oxyacids, oxygen, and trace metal ions such as Fe(III) or Mn(II) can take place in a flue gas wet scrubber. Identifying all reactions involved in this complex system is impossible. However, important reactions must be identified and characterized in order to improve the performance of a scrubber. 

PURPOSE OF EXPERIMENT Prepare and/or study some properties and reactions of oxyacids, oxyanions, and oxides of nitrogen, and determine the unknown metal in a metal oxide that you prepare. 

Nitric acid is a strong oxidizing agent. Most metals are converted to their nitrates with the evolution of oxides of nitrogen (the composition of the mixture of the oxides depends on the temperature and on the concentration of the nitric acid used). Some nonmetals (e.g. sulfur and phosphorus) react to produce oxyacids. 

Difficulties are encountered in determining NO2 using the ozone-chemiluminescence technique due to the non-specific conversion of several nitrogen oxides/oxyacids on the Mo catalyst. Use of FeS04 f°r N02-to-N0 conversion has been described, but humidity-dependent sorption/desorption effects have been reported, e.g., PAN (11). Alternatively, a commercial NO2 analyzer based on surface chemiluminescence of NO2 in the presence of a luminol solution, has been introduced which exhibits the requisite sensitively and selectivity. 

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