<\/p>\n\n\n\n
Nitric acid reacts with most metals, but the details depend on the concentration of the acid and the nature of the metal. Dilute nitric acid behaves as a typical\u00a0acid\u00a0in its reaction with most metals.\u00a0Magnesium,\u00a0manganese, and\u00a0zinc\u00a0liberate\u00a0H2:<\/p>\n\n\n\n
Mg + 2 HNO3\u00a0\u2192\u00a0Mg(NO3)2\u00a0+ H2<\/p>\n\n\n\n
Mn + 2 HNO3\u00a0\u2192\u00a0Mn(NO3)2\u00a0+ H2<\/p>\n\n\n\n
Zn + 2 HNO3\u00a0\u2192\u00a0Zn(NO3)2\u00a0+ H2<\/p>\n\n\n\n
Nitric acid can oxidize non-active metals such as\u00a0copper\u00a0and\u00a0silver. With these non-active or less electropositive metals the products depend on temperature and the acid concentration. For example, copper reacts with dilute nitric acid at ambient temperatures with a 3:8 stoichiometry:<\/p>\n\n\n\n
3 Cu + 8 HNO3 \u2192 3 Cu(NO3)2 + 2 NO + 4 H2O<\/p>\n\n\n\n
The\u00a0nitric oxide\u00a0produced may react with atmospheric\u00a0oxygen\u00a0to give\u00a0nitrogen dioxide. With more concentrated nitric acid, nitrogen dioxide is produced directly in a reaction with 1:4 stoichiometry:<\/p>\n\n\n\n
Cu + 4 H+ + 2 NO\u22123 \u2192 Cu2+ + 2 NO2 + 2 H2O<\/p>\n\n\n\n
Upon reaction with nitric acid, most metals give the corresponding\u00a0nitrates. Some\u00a0metalloids\u00a0and\u00a0metals\u00a0give the\u00a0oxides; for instance,\u00a0Sn,\u00a0As,\u00a0Sb, and\u00a0Ti\u00a0are oxidized into\u00a0SnO2,\u00a0As2O5,\u00a0Sb2O5, and\u00a0TiO2\u00a0respectively.<\/p>\n\n\n\n
Some\u00a0precious metals, such as pure\u00a0gold\u00a0and platinum-group metals do not react with nitric acid, though pure gold does react with\u00a0aqua regia, a mixture of concentrated nitric acid and\u00a0hydrochloric acid. However, some less noble metals (Ag,\u00a0Cu, …) present in some\u00a0gold alloys\u00a0relatively poor in gold such as\u00a0colored gold\u00a0can be easily oxidized and dissolved by nitric acid, leading to colour changes of the gold-alloy surface. Nitric acid is used as a cheap means in\u00a0jewelry\u00a0shops to quickly spot low-gold alloys (<\u00a014\u00a0karats) and to rapidly assess the gold purity.<\/p>\n\n\n\n
Being a powerful oxidizing agent, nitric acid reacts with many non-metallic compounds, sometimes explosively. Depending on the acid concentration, temperature and the\u00a0reducing agent\u00a0involved, the end products can be variable. Reaction takes place with all metals except the\u00a0noble metals\u00a0series and certain\u00a0alloys. As a general rule, oxidizing reactions occur primarily with the concentrated acid, favoring the formation of nitrogen dioxide (NO2). However, the powerful oxidizing properties of nitric acid are\u00a0thermodynamic\u00a0in nature, but sometimes its oxidation reactions are rather\u00a0kinetically\u00a0non-favored. The presence of small amounts of\u00a0nitrous acid\u00a0(HNO2) greatly increases the rate of reaction.<\/p>\n\n\n\n
Although\u00a0chromium\u00a0(Cr),\u00a0iron\u00a0(Fe), and\u00a0aluminium\u00a0(Al) readily dissolve in dilute nitric acid, the concentrated acid forms a metal-oxide layer that protects the bulk of the metal from further oxidation. The formation of this protective layer is called\u00a0passivation.\u00a0Typical passivation concentrations range from 20% to 50% by volume.[full citation needed]\u00a0Metals that are passivated by concentrated nitric acid are\u00a0iron,\u00a0cobalt,\u00a0chromium,\u00a0nickel, and\u00a0aluminium.<\/p>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Nitric acid reacts with most metals, but the details depend on the concentration of the acid and the nature of the metal. Dilute nitric acid behaves as a typical\u00a0acid\u00a0in its reaction with most metals.\u00a0Magnesium,\u00a0manganese, and\u00a0zinc\u00a0liberate\u00a0H2: Mg + 2 HNO3\u00a0\u2192\u00a0Mg(NO3)2\u00a0+ H2 Mn + 2 HNO3\u00a0\u2192\u00a0Mn(NO3)2\u00a0+ H2 Zn + 2 HNO3\u00a0\u2192\u00a0Zn(NO3)2\u00a0+ H2 Nitric acid can oxidize non-active […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[],"class_list":["post-393","post","type-post","status-publish","format-standard","hentry","category-product-introduction"],"blocksy_meta":[],"yoast_head":"\n