CFC's and Ozone Depletion Questions and Answers 2023

CFC's and Ozone Depletion Questions and Answers 2023 What is the full name for "CFCs"? Chlorofluorocarbon Why were CFCs developed and how were they used? Humans synthesized the production of CFCs because they are nontoxic, nonflammable, cheap and widely available. They revolutionized air conditioning making it readily accessible for homes, offices, schools, cars etc. CFC technology transformed the economy as it spurred the growth of humid/hot countries. Chemical Formula for CFC ... DRAW: Molecular Structure of a CFC Molecule Cl F - C - F Cl CFCs became very widely used because they are chemically unreactive. How is this lack of reactivity connected to the problem of ozone depletion? The C-Cl bonds and C-F bonds in CFCs are so strong that molecules are virtually indestructible. E.g. an average CCl2F2 molecule can persist in the atmosphere for 120 years before it is decomposed. It only takes about five years for atmospheric wind currents to bring molecules up to the stratosphere which is where the CFC molecules end up, leading to ozone depletion. Write the series of chemical reactions that were proposed by Sherwood Rowland and Mario Molina to explain ozone depletion by CFCs. see page 94 What is the chemical definition of a radical? A highly reactive chemical species with one or more unpaired electrons. Often indicated with a dot. Why are radicals so reactive? Because of the unpaired electron as they are ready to participate in many reactions. How can a single CFC molecule be responsible for destroying thousands of ozone molecules? The chlorine atoms has seven outer electrons and exhibits a strong tendency to achieve a stable octet by sharing electrons with another atom. This reactivity causes a series of reactions: Pulls an oxygen atom away from an ozone molecule to from chlorine monoxide and oxygen molecule. Chlorine monoxide is another free radical and this joins to another chlorine monoxide which decomposes ozone to oxygen. COMPLEX INTERACTION OF OZONE WITH ATOMIC CHLORINE PROVIDES A PATHWAY FOR THE DESTRUCTION OF OZONE. What measurement was the "smoking gun" that provided the role of CFC's in causing ozone depletion? Rowland-Molina found a striking piece of evidence: saw two sets of data from the Antarctic, one for ozone concentration and the other for chlorine monoxide. As stratospheric ozone concentration decreases the concentration of stratospheric chlorine increases; two curves on the graph mirrored each other perfectly. The major effect was a decrease in ozone and an increase in chlorine monoxide. Why does the ozone hole occur over the Antarctic? A special set of conditions exist in Antarctica: the lower stratosphere over the South Pole is the coldest spot on Earth. From June to September, the winds that circulate the South Pole form a vortex that prevents warmer air from entering the region. Polar stratospheric clouds form and these are composed of tiny ice crystals formed from the small amount of water vapor present in the stratosphere. The chemical reactions that occur on the surface of these nice crystals convert molecules that do not deplete ozone to the more reactive species that do (such as chlorine). Why is the ozone hole reach its largest size in September/October? When sunlight returns in late september, the light splits HOCL and Cl2 to release chlorine atoms - which destroys ozone at a rapid rate.