Question

The starting material in Birkeland and Eyde process for manufacture of nitric acid is:
A. Ammonia
B. Nitrogen dioxide gas
C. Air
D. Chile saltpetre

Answer 1

Hint: Nitric acid is formed by oxidation of a nitrogen source. Look at the options and decide which nitrogen source can be converted to nitric acid most easily and quickly.

Complete step by step answer:
The Birkeland–Eyde process is usually done for the manufacture of nitric acid. It is also used in the production of nitrogen-based fertilizer.
The first step is the conversion of atmospheric nitrogen (${{\text{N}}_{\text{2}}}$) to soluble nitrates.
${{\text{N}}_{\text{2}}}\text{+}{{\text{O}}_{\text{2}}}\to \text{2NO}$
Then, the hot nitric oxide is cooled and it is combined with atmospheric oxygen to produce nitrogen dioxide.
$\text{2NO+}{{\text{O}}_{\text{2}}}\to \text{2N}{{\text{O}}_{\text{2}}}$
The nitrogen dioxide produced is then dissolved in water that further gives nitric acid ($\text{HN}{{\text{O}}_{3}}$), which is then purified and concentrated by fractional distillation
$\text{3N}{{\text{O}}_{\text{2}}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\to \text{2HN}{{\text{O}}_{\text{3}}}\text{+NO}$
Birkeland–Eyde process is generally used to fix atmospheric nitrogen (${{\text{N}}_{\text{2}}}$) into nitric acid ($\text{HN}{{\text{O}}_{3}}$), one of several chemical processes generally referred to as nitrogen fixation. The resultant nitric acid is then used as a source of nitrate ($\text{NO}_{3}^{-}$) in the reaction:
$\text{HN}{{\text{O}}_{3}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\to {{\text{H}}_{\text{3}}}{{\text{O}}^{+}}\text{+NO}_{3}^{-}$
Therefore, the answer is – option (B) – The starting material in Birkeland and Eyde process for manufacture of nitric acid ($\text{HN}{{\text{O}}_{3}}$) is Nitrogen dioxide gas ($\text{N}{{\text{O}}_{\text{2}}}$).

Additional information:
Nitric acid ($\text{HN}{{\text{O}}_{3}}$) is yellow in color due to presence of dissolved nitrogen dioxide ($\text{N}{{\text{O}}_{\text{2}}}$) in nitric acid.

Note: The Ostwald process is another chemical process used for manufacture of nitric acid ($\text{HN}{{\text{O}}_{3}}$). The reaction occurring in this process is given as –
$2N{{H}_{3}}(g)+4{{O}_{2}}(g)\text{+}{{\text{H}}_{\text{2}}}\text{O(l)}\to 3{{\text{H}}_{\text{2}}}\text{O}(g)+2\text{HN}{{\text{O}}_{3}}(aq)$