Nitric acid

Nitric acid is a very strong oxidant. It begins to decompose even at ordinary temperature: heating accelerates the decomposition after the reaction:

If you immerse the burned chips in nitric acid, then it burns vigorously

2HNO3 = H2O + 2NO2 + O.

Therefore, nitric acid always releases a brown gas of nitrogen dioxide, smokes in the air and acts as a strong oxidizer.

If you immerse the burned chips in nitric acid, then it burns vigorously. To demonstrate this experiment, a large test tube is anchored in the foot of the iron support, into which are poured a few milliliters of concentrated HNO3 with a density of 1,5. Such acid is usually obtained by distillation in a retort of sodium nitrate and concentrated sulfuric acid with a density of 1,84.

The chips are ignited and immersed in nitric acid. Burning continues; at the same time NO2 and smoke from the combustion of chips are released.

Nitric acid is mixed with water in any proportions. In aqueous solutions, it almost completely dissociates into ions. Forms with water an azeotropic mixture with a concentration of 68,4% and tboiling 1200 C at a normal atmospheric pressure.

Gold, some metals platinum group and tantalum are inert to nitric acid in the whole range of concentrations, other metals react with it , the course of the reaction is determined by its concentration. HNO3 as a strong monobasic acid interacts with basic and amphoteric oxides, with bases, displaces weak acids from their salts. HNO3 in any concentration shows the properties of the acid-oxidant, while nitrogen is reduced to an oxidation state of +4 to -3. The depth of recovery depends primarily on the nature of the reducing agent and on the concentration of HNO3.

The modern method of nitric acid production is based on catalytic oxidation of synthetic ammonia on platinum-rhodium catalysts (Ostwald process) to a mixture of nitrogen oxides (nitrous gases), with further absorption of water.

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