A nitrite ion is an inorganic compound that is composed of nitrogen and oxygen. Let us discuss the nitrite ion formula. The chemical formula for the nitrite ion is NO2-. In food industries, nitrite of Sodium is commonly employed as a curing agent. Sodium nitrite or nitrate is responsible for the colour and flavour of cooked cured meats. In nature, the nitrite anion is a common intermediary in the nitrogen cycle. Nitrite also refers to chemical molecules containing the -ONO group, which are nitrous acid esters.
Chemical Elements Used in Writing Formula for Nitrite
The Elements that are included in the formula for nitrite are Nitrogen and Oxygen. For writing its formula a clear idea of the valencies of both nitrogen and oxygen is required.
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As we know, the symbol of nitrite is NO2-. The nitrite ion has a symmetrical structure (C2v symmetry), with equal length N–O links and a bond angle of roughly 115 degrees. It's described as a resonance hybrid in valence bond theory, with equal contributions from two canonical forms that are mirror reflections of one another. There is a sigma bond between each oxygen atom and the nitrogen atom in molecular orbital theory, as well as a delocalized pi link generated from the p orbitals on nitrogen and oxygen atoms that is perpendicular to the molecule's plane. The ion's negative charge is evenly divided between the two oxygen atoms. A lone pair of electrons is carried by both nitrogen and oxygen atoms. The nitrite ion is thus a Lewis base.
Properties of Nitrite
The conjugate base of the weak acid nitrous acid is nitrite:
HNO2 ⇌ H+ + NO2-; pKa ≈ 3.3at 18 °C
3HNO2 (aq) ⇌ H3O+ + NO3- + 2NO
At 0 °C, this reaction is sluggish. Making nitric oxide (NO) in the lab involves adding acid to a nitrite solution in the presence of a reducing agent, such as iron(II).
The nitrogen atom in nitrite has a formal oxidation state of +3. This means it can be oxidised to +4 and +5 oxidation levels, or reduced to oxidation levels as low as 3. The table below shows the standard reduction potentials for processes that directly involve nitrous acid: Consider the following scenario:
H2N2O2 + 2 H+ + 2 e- ⇌ N2 + 2 H2O; E0 = +2.65 V
When nitrogen is in the oxidation state +5, oxidation reactions usually result in the creation of the nitrate ion. For quantitative analysis of nitrite (by titration), for example, oxidation with permanganate ion can be used:
5 NO2- + 2 MnO4- + 6 H+ → 5 NO3- + 2 Mn2+ + 3 H2O
Reduction reactions with nitrite ion produce a variety of products, depending on the reducing agent and its intensity. With sulphur dioxide, the products are NO and N2O; with tin(II) (Sn2+), the product is hyponitrous acid (H2N2O2); and with hydrogen sulphide, the product is ammonia (NH3). The result of nitrite reduction with the hydrazinium cation (N2H5+) is hydrazoic acid (HN3), an unstable and explosive compound:
HNO2 + N2H5+ → HN3 + H2O + H3O+
which can also react with nitrite in the following way:
HNO2 + HN3 → N2O + N2 + H2O
This reaction is unique since it incorporates nitrogen molecules in four different oxidation states.
Did You Know?
The preservative sodium nitrite protects ham, salami, and other processed and cured meats from dangerous microorganisms while also giving them their pink hue. However, nitrite can damage cells and develop into cancer-causing chemicals in the human body under specific situations.