Question

Dinitrogen is a robust compound, but reacts at high altitude to form oxides. The oxide of nitrogen that can damage plant leaves and retard photosynthesis is:

• A. NO
• B. NO$_3^-$
• C. NO$_2$
• D. NO$_2^-$

Hint:

NO$_2$ is a major air pollutant that causes photochemical smog and acid rain.

Answer 1

The Correct Option is C

Step 1: Understanding Nitrogen Oxide Formation
Dinitrogen (N$_2$) reacts with oxygen (O$_2$) at high altitudes to form nitrogen oxides. The reaction occurs as follows: \[ N_2 (g) + O_2 (g) \rightarrow 2NO (g) \] Step 2: Conversion to NO$_2$
Nitric oxide (NO) further reacts with oxygen: \[ 2NO (g) + O_2 (g) \rightarrow 2NO_2 (g) \] Nitrogen dioxide (NO$_2$) is a toxic gas that damages plant leaves and hinders photosynthesis. Thus, the correct answer is (C).

Answer 2

Step 1: Understanding the context
Dinitrogen (N₂) is a very stable molecule due to the strong triple bond between the nitrogen atoms.
However, at high altitudes, it can react with oxygen to form various nitrogen oxides.

Step 2: Common nitrogen oxides
Some common nitrogen oxides include NO, NO₂, N₂O, and N₂O₅.
Among these, nitrogen dioxide (NO₂) is known for its harmful effects on plants.

Step 3: Effect of NO₂ on plants
NO₂ is a toxic gas that can cause damage to plant leaves.
It interferes with photosynthesis by damaging chlorophyll and reducing the plant's ability to produce food.

Step 4: Conclusion
Therefore, the nitrogen oxide that damages plant leaves and retards photosynthesis is NO₂.