Nitric acid gold purity. Being a powerful oxidizing agent, nitric acid reacts violently with many non-metallic compounds, and the reactions may be explosive. Depending on the acid concentration, temperature and the reducing agent involved, the end products can be variable. Reaction takes place with all metals except the noble metals series and certain alloys. As a general rule, oxidizing reactions occur primarily with the concentrated acid, favoring the formation of nitrogen dioxide (NO). However, the powerful oxidizing properties of nitric acid are thermodynamic in nature, but sometimes its oxidation reactions are rather kinetically non-favored. The presence of small amounts of nitrous acid
Acid–base reaction Instead of defining acid–base reactions in terms of protons or other bonded substances, the Lewis definition defines a base (referred to as a "Lewis base") to be a compound that can donate an "electron pair", and an acid (a "Lewis acid") to be a compound that can receive this electron pair. For example, boron trifluoride, BF is a typical Lewis acid. It can accept a pair of electrons as it has a vacancy in its octet. The fluoride ion has a full octet and can donate a pair of electrons. Thus is a typical Lewis acid, Lewis base reaction. All