alleryStart learning →Nitrogen makes up most of the air, yet plants cannot use it directly. What has to happen first?
AIt must be fixed into a bioavailable form
BIt must be cooled until it becomes a liquid
CIt must be split by sunlight into free atoms
DIt must be dissolved in rain to reach the soil
Answer & Solution
Correct answer: A. It must be fixed into a bioavailable form
1. Diatomic nitrogen accounts for 78 percent of air, yet plants cannot take it up as a nutrient.
2. The barrier is the great stability of the nitrogen to nitrogen triple bond.
3. The gas must first be converted into a more bioavailable form, a step called nitrogen fixation.
4. Ammonia is such a form, and it is the one plants absorb most easily.
5. Cooling nitrogen to a liquid changes its state but leaves the triple bond intact.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 13 "Fundamental Equilibrium Concepts", section 13.3 Shifting Equilibria: Le Châtelier's Principle_
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