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How is Nitric Acid Made?

Nitric acid is made from the reaction of ammonia with oxygen.

The first stage produces nitrogen monoxide.
(The same gas is formed as a pollutant in petrol engines).

A hot platinum catalyst is used (about 850 °C).
The reaction is highly exothermic and the heat given out by
the reaction is sufficient to keep the reaction going.

ammonia + oxygen  arrow  nitrogen monoxide  + water.
4NH3(g)  +  5O2(g)     arrow          4NO(g)     +    6H2O(g)

The second stage involves the reaction of
nitrogen monoxide with more oxygen.

nitrogen monoxide + oxygen   arrow  nitrogen dioxide.
2NO(g)         +         O2(g)     arrow          2NO2(g)

Finally, nitrogen dioxide reacts with water and more oxygen.

nitrogen dioxide  +  oxygen   +   water    arrow  nitric acid.
4NO2(g)          +          O2(g)  +  2H2O(l)   arrow  4HNO3(aq)

The overall reaction is

ammonia  oxygen    arrow    nitric acid     +    water.
4NH3(g)    +   8O2(g)     arrow      4HNO
3(aq)    +  4H2O(l)

This is the oxidation of ammonia to produce nitric acid.

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