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The nitrogen cycle on Earth is a biogeochemical cycle of events that continuously removes unreactive nitrogen gas from the atmosphere and converts it into more reactive chemicals in soil that are used by plants - Leaving Cert Chemistry - Question A - 2021
Question A
The nitrogen cycle on Earth is a biogeochemical cycle of events that continuously removes unreactive nitrogen gas from the atmosphere and converts it into more react... show full transcript
Worked Solution & Example Answer:The nitrogen cycle on Earth is a biogeochemical cycle of events that continuously removes unreactive nitrogen gas from the atmosphere and converts it into more reactive chemicals in soil that are used by plants - Leaving Cert Chemistry - Question A - 2021
Step 1
Why is nitrogen gas unreactive?
Answer
Nitrogen gas (N₂) is unreactive due to its very strong triple bond, which requires a significant amount of energy to break. Additionally, it is non-polar, has a high degree of symmetry, and presents no dipole moment, meaning there are no unpaired electrons available for reaction.
Step 2
Describe, using equations or otherwise, how lightning generates the gases NO and NO₂ in the atmosphere.
Answer
Lightning provides sufficient energy to break the triple bond of nitrogen gas (N₂). This enables nitrogen to react with oxygen (O₂) in the following reactions:
- N₂ + O₂ → 2 NO (Nitric oxide formation)
- 2 NO + O₂ → 2 NO₂ (Nitrogen dioxide formation)
Hence, the formation of nitrogen monoxide (NO) and nitrogen dioxide (NO₂) occurs.
Step 3
Write a balanced equation for the reaction of NO₂ with water forming acid rain.
Answer
The balanced equation for the reaction of nitrogen dioxide with water can be represented as follows:
ightarrow 2 ext{HNO}_3 + ext{NO}$$ This reaction produces nitric acid, which contributes to acid rain.Step 4
Step 5
Describe one pathway by which nitrogen in animals is restored to the atmosphere completing the nitrogen cycle.
Answer
One pathway for restoring nitrogen from animals back to the atmosphere is through the process of decomposition. When animals die, their bodies decompose, releasing nitrogen back into the soil as ammonium compounds. Additionally, nitrifying bacteria can convert these compounds into nitrates and eventually into nitrogen gas (N₂) through denitrification, completing the nitrogen cycle.