The hydroxyl radical, OH, is formed at low altitudes via the reaction of excited oxygen atoms with water:

(a) Write the Lewis structure for the hydroxyl radical. Once produced, the hydroxyl radical is very reactive. Explain why each of the following series of reactions affects the pollution in the troposphere:
(b) OH + NO2 †’ HNO3
(c) OH + CO + O2 †’ CO2 + OOH
OOH + NO †’ OH + NO2
(d) OH + CH4 †’ H2O + CH3
CH3 + O2 †’ OOCH3
OOCH3 + NO †’ OCH3 + NO2
(e) The concentration of hydroxyl radicals in the troposphere is approximately 2 × 106 radicals per cm3. This estimate is based on a method called long path absorption spectroscopy (LPAS), similar in principle to the Beer's law measurement discussed in the Closer Look essay on p. 564, except that the path length in the LPAS measurement is 20 km. Why must the path length be so large?

Transcribed Image Text:

O"(g) + H2O(g) 20H(g)