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Nitrogen Oxo-Acids

Just as there is a range of neutral nitrogen-oxygen compounds with the nitrogen in a corresponding range of oxidation states, so too there is with nitrogen oxy-anions.

The most important are the nitrate anion, NO3-, occurring largely as nitric acid, and the nitrite anion, NO2-, occurring largely as nitrous acid.

Nitrate (NO3-)

The oxidation state of N is +5. This has a planar, D3h, structure, and acts as a very weak base but strong oxidizing agent. This is found mainly as nitric acid, which is manufactured by the Ostwald process, and is used in the production of fertilizers, explosives, and other nitrated compounds.

 

The Ostwald process:

Reactions of Nitric Acid

As oxidizing agent, in solution [N(+5) to N(+4)]
With strong reducing agent, eg. Zn [N(+5) to N(-3)] 
With weaker reducing agent, eg. Cu [N(+5) to N(+4)]
With weak reducing agent, in dilute acid [N(+5) to N(+2)]

Nitronium (NO2+)

The oxidation state of N is +5. This has a symmetric linear structure, and acts as an oxidizing agent, a nitrating agent, and a Lewis acid.

Nitrite (NO2-)

The oxidation state of N is +3. This has the bent, C2v, structure of water, and acts as a weak base, and as an oxidizing agent and a reducing agent.

Nitrosonium (NO+)

The oxidation state of N is +3. This has an asymmetric, linear structure, and acts as an oxidizing agent and a Lewis acid.

Hyponitrite (N2O22-)

The oxidation state of N is +1. This has the C2h structure, and acts as a reducing agent.

The oxidizing and reducing properties of the nitrogen oxy-anions can be summarized in a Frost Diagram. This shows the standard electronic potential for the redox couple of an species of a given oxidation number with the species in the zero oxidation state, and its dependence on the oxidation number.

Nitrogen Frost Diagram

The blue line is for nitrogen oxides in acidic solution, and the black line for basic solution.