Question

During night, in troposphere, which of the following is/are NOT correct?

• A. $\text{NO}_2 + h\nu \rightarrow \text{NO} + \text{O}$
• B. Most of the NOx (i.e., NO + NO\(_2\)) converts to NO
• C. NO + O\(_3\) $\rightarrow$ NO\(_2\) + O\(_2\)
• D. Most of the NOx (i.e., NO + NO\(_2\)) converts to NO\(_2$)

Hint:

NO\(_2\) photolysis happens only in sunlight. At night, NO is rapidly converted to NO\(_2\) by reaction with ozone.

Answer 1

The Correct Option is B

Option (A): NOT correct
During night, no sunlight exists. Photolysis reaction
\[ \text{NO}_2 + h\nu \rightarrow \text{NO} + \text{O} \] does not occur. Hence, (A) is NOT correct.
Option (B): NOT correct
At night, NO reacts with O\(_3\) to form NO\(_2\). Thus NO\(_2\) dominates, not NO. So “NOx converts mostly to NO” is incorrect.
Option (C): Correct
This reaction does occur at night:
\[ \text{NO} + \text{O}_3 \rightarrow \text{NO}_2 + \text{O}_2 \]
Option (D): Correct
Since NO converts to NO\(_2\) by reacting with ozone, NO\(_2\) becomes dominant.
Thus, the statements that are NOT correct are (A) and (B).
Final Answer: (A), (B)