Acidic oxide Some non-metal oxides, such as nitrous oxide (NO) and carbon monoxide (CO), do not display any acid/base characteristics. Acidic oxides can also react with basic oxides to produce salts of oxoanions: Acidic oxides are environmentally relevant. Sulfur and nitrogen oxides are considered air pollutants as they react with atmospheric water vapour to produce acid rain. Although it is difficult to classify these oxides as acids, the property is manifest in reactions with bases. For example, carbon dioxide reacts with alkali. For this reason, alkali is kept in stoppered vessels to inhibit reaction with atmospheric carbon dioxide. In geochemistry complex silicates
Nitrogen dioxide This reaction is negligibly slow at low concentrations of NO characteristic of the ambient atmosphere, although it does proceed upon NO uptake to surfaces. Such surface reaction is thought to produce gaseous HNO (often written as HONO) in outdoor and indoor environments. Nitric acid decomposes slowly to nitrogen dioxide by the overall reaction: The nitrogen dioxide so formed confers the characteristic yellow color often exhibited by this acid. is used to generate anhydrous metal nitrates from the oxides: Alkyl and metal iodides give the corresponding nitrites: is introduced into the environment by natural causes, including entry from the stratosphere, bacterial