Q22.12P - Chemistry: Molecular Nature Of Matter And Change

Question

Describe three pathways for the utilization of atmospheric nitrogen. Is human activity a significant factor? Explain.

Step-by-Step Solution

Answer

Atmospheric fixation, industrial fixation, and biological fixation are the three methods for removing nitrogen from the atmosphere.

Water contamination is caused by human activities, such as the overuse of fertilisers and automobiles.

Step 1: Atmosphere

The gases that surround a star or planetary body are held in place by gravity and are referred to as the atmosphere. If gravity is high and the temperature of the atmosphere is low, a body is more likely to keep an atmosphere over time.

Step 2: Explanation

Atmospheric fixation, industrial fixation, and biological fixation are the three methods for utilising atmospheric nitrogen. The following paragraphs detail each procedure.

Human activity is a significant contributor to the overall quantity of fixed nitrogen in the atmosphere. Artificially manufactured nitrogen-based fertiliser (ammonia, urea, ammonium salts) is taken up by plants and enters the biosphere.

The considerable rise in vehicle traffic also contributes to total nitrogen fixed, as high engine running temperatures resemble lightning, causing $\mathrm{NO}$ to develop from the air taken in to burn the hydrocarbon fuel. Overuse of fertilisers and cars are major sources of water contamination. Nitrate from fertiliser and vehicle operation leaches into natural waters, causing eutrophication—the depletion of oxygen and the death of aquatic animal life—as a result of excessive algal and plant growth and degradation.

Step 3: Explanation of pathways

a. Atmospheric fixation entails high-temperature endothermic processes including the conversion of ${\mathrm{N}}_2$ and ${\mathrm{O}}_2$ to $\mathrm{NO}$ which is then oxidised exothermically by ozone to generate ${\mathrm{NO}}_2$.${\mathrm{NO}}_2$ interacts with a hydroxyl radical to generate ${\mathrm{HNO}}_3$ during the day.

$$\begin{gathered} {\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2\mathrm{NO}\left(\mathrm{g}\right) \\ \mathrm{NO}\left(\mathrm{g}\right)+{\mathrm{O}}_3\left(\mathrm{g}\right)\to {\mathrm{NO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right) \\ {\mathrm{NO}}_2\left(\mathrm{g}\right)+\mathrm{HO}\times \left(\mathrm{g}\right)\to {\mathrm{HNO}}_3\left(\mathrm{g}\right) \end{gathered}$$

The acid is then carried down by rain and enters both the sea and the land as ${\mathrm{NO}}_3^{-}$, which plants can use.

b. Industrial fixing usually entails the Haber process, which produces ammonia. A metal catalyst converts gaseous nitrogen and hydrogen to ammonia under high pressure and temperature.

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3\left(\mathrm{g}\right)$

While some of the ${\mathrm{NH}}_3$ is transformed to ${\mathrm{HNO}}_3$ the majority of the ammonia is used as a fertiliser, either directly or as urea and ammonium salts (sulphate, phosphate, nitrate).

c. The most prevalent method of fixing atmospheric ${\mathrm{N}}_2$is biological fixation. It's found in blue-green algae and nitrogen-fixing bacteria found on leguminous plant roots. A sequence of enzymes in root bacteria repair ${\mathrm{N}}_2$ by converting it to ${\mathrm{NH}}_3$ and ${\mathrm{NH}}_4^{+}$. Other soil bacteria have enzymes that catalyse the multistep oxidation of ${\mathrm{NH}}_4^{+}$to ${\mathrm{NO}}_2^{-}$,  finally ${\mathrm{NO}}_3^{-}$which plants then decrease to generate their protein. Animals consume plant proteins in order to produce their own proteins and excrete nitrogenous waste such as urea.

Therefore, human activities are significant factor for water pollution. And the three pathways for nitrogen fixation are atmospheric fixation, industrial fixation and biological fixation.