What is Nitrogen dioxide?
[[File:Diossido di azoto.jpg|thumb|Nitrogen dioxide gas in a test tube]] '''Nitrogen dioxide''' is a [[chemical compound]]. Its chemical formula is NO<sub>2</sub>. It contains [[nitrogen]] and [[oxide]] [[ion]]s. The nitrogen is in the +4 [[oxidation state]]. [[File:Nitrogen-dioxide-3D-balls.png|thumb|Nitrogen dioxide structure]] ==Properties== [[File:NO2-N2O4.jpg|thumb|The left hand bottle contains more nitrogen dioxide than the Tetroxide, whereas the Second bottle's contents' state favors the formation of more Dinitrogen Tetroxide (colorless) than Nitrogen Dioxide (Red/Brown).]] Nitrogen Dioxide is a reddish-brown gas with a distinct, pungent odor similar to that of Chlorine. It causes significant and damaging pulmonary effects when it is inhaled, due to the formation of both Nitric (HNO3) & Nitrous (HNO2) acids when it reacts with Water present in the lungs. When Nitrogen Dioxide is compressed or cooled to near 0° C, two molecules of the Dioxide bond, forming the colorless [[Dinitrogen Tetroxide]]. It is a strong [[oxidizing agent]]. Upon heating, Nitrogen Dioxide decomposes back into lower oxides of Nitrogen (NO) as well as Oxygen. It reacts with [[iodide]]s to form [[nitrite]]s and elemental [[iodine]]. The presence of NO2 in concentrated Nitric acid causes the acid to take on a yellow color, depending on the concentration of the dissolved gas. ==Preparation== Nitrogen dioxide is normally made by [[oxidation]] of [[nitric oxide]] by [[oxygen]] in air. It can also be made by heating some [[nitrate]]s. It can be made by reacting concentrated [[nitric acid]] with [[copper]] or [[tin]]. ==Uses== It is used to make nitric acid by dissolving it in water. Nitric oxide is also released. ==Safety== Nitrogen dioxide is very toxic. It has a foul odor, which aids in its detection. Much care should be taken to avoid contact with this compound. ==Related pages== *[[Nitrous oxide]] *[[Nitrous acid]] [[Category:Nitrogen compounds]] [[Category:Oxides]]