For example, copper reacts with dilute nitric acid at ambient temperatures with a 3:8 stoichiometry:ģ Cu + 8 HNO 3 → 3 Cu(NO 3) 2 + 2 NO + 4 H 2O With these non-active or less electropositive metals the products depend on temperature and the acid concentration. Nitric acid can oxidize non-active metals such as copper and silver. Magnesium, manganese, and zinc liberate H 2: Dilute nitric acid behaves as a typical acid in its reaction with most metals. Nitric acid reacts with most metals, but the details depend on the concentration of the acid and the nature of the metal. Since nitric acid has both acidic and basic properties, it can undergo an autoprotolysis reaction, similar to the self-ionization of water:Ģ HNO 3 ⇌ + + NO − 3 + H 2O Reactions with metals The nitronium ion, +, is the active reagent in aromatic nitration reactions. HNO 3 + 2 H 2SO 4 ⇌ + + + + 2 HSO − 4 Equilibrium constant: K ≈ 22 Nitric acid can act as a base with respect to an acid such as sulfuric acid: The p K a value rises to 1 at a temperature of 250 ☌. ![]() This means that the nitric acid in diluted solution is fully dissociated except in extremely acidic solutions. There is some disagreement over the value of the acid dissociation constant, though the p K a value is usually reported as less than −1. Nitric acid is normally considered to be a strong acid at ambient temperatures. The third N–O bond is elongated because its O atom is bonded to H atom. This can be explained by theories of resonance the two major canonical forms show some double bond character in these two bonds, causing them to be shorter than single N–O bonds. Two of the N–O bonds (two N–O bonds with terminal O atoms) are equivalent and relatively short. Two major resonance representations of HNO 3 H 2O or oxonium nitrate + − and the trihydrate HNO 3♳H 2O.Īn older density scale is occasionally seen, with concentrated nitric acid specified as 42 Baumé.Two solid hydrates are known: the monohydrate HNO 3 The azeotrope of nitric acid and water is a colourless liquid at room temperature. It is known as "concentrated nitric acid". This solution has a boiling temperature of 120.5 ☌ (249 ☏) at 1 atm. 4.1 Precursor to organic nitrogen compoundsĬommercially available nitric acid is an azeotrope with water at a concentration of 68% HNO 3. ![]() 1.1 Contamination with nitrogen dioxide.Nitric acid is also commonly used as a strong oxidizing agent. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%. When the solution contains more than 86% HNO 3, it is referred to as fuming nitric acid. ![]() Most commercially available nitric acid has a concentration of 68% in water. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Nitric acid is the inorganic compound with the formula H N O 3.
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