The stratospheric ozone layer plays an important role in absorbing high-energy ultraviolet radiation that would be harmful to living systems on the earth’s surface. The concentration of ozone in the stratosphere is determined by both thermal and photochemical pathways for its decomposition. Nitric oxide, NO, is a trace constituent in the stratosphere. NO reacts with ozone to form nitrogen dioxide, NO2, and the diatomic oxygen molecule. The nitrogen-oxygen bond in NO2 is relatively weak. When an NO2 molecule encounters an oxygen atom, it transfers an oxygen, forming O2 and NO. The chemical reactions involved are formations of NO2 following by reaction of NO2 with atomic oxygen for form NO and O2. When we add these two reactions together, we see that the overall reaction is simply the reaction of ozone with atomic oxygen to form two molecules of molecular oxygen. In this case, NO serves as a catalyst, a substance that affects the overall rate of a chemical reaction without itself undergoing a permanent change. Nitric oxide speeds up the rate of overall decomposition because it is continuously recycled through the two reactions we have just shown.
Scientific and Medical Animations
Copyright ©2017 ALL RIGHTS RESERVED