Regarding this, what causes nitric acid?
Nitric acid is made by reaction of nitrogen dioxide (NO2) with water. Normally, the nitric oxide produced by the reaction is reoxidized by the oxygen in air to produce additional nitrogen dioxide. Bubbling nitrogen dioxide through hydrogen peroxide can help to improve acid yield.
Where is nitric acid used?
Nitric acid is used in the production of ammonium nitrate for fertilizers, making plastics, and in the manufacture of dyes. It is also used for making explosives such as nitroglycerin and TNT. When it is combined with hydrochloric acid, an element called aqua regia is formed.