Rate and Rates of Reaction

How does the ozone hole arise We must consider the role of species other than the allotropes of oxygen in the Chapman cycle. There is evidence that chlorine and bromine in the stratosphere lead to a decrease in the amount of ozone present. How does this occur What factors influence whether or not the decrease occurs And what might be done to combat the loss of ozone These questions all point to aspects of chemical kinetics that we will address in this chapter. To begin this study, we focus first on the concepts of rate of reaction and the ways in which reaction rate can be measured. 

We suggested that the rates of different chemical reactions govern ozone levels in the atmosphere, and this seems sensible. If ozone—or anything else—is produced faster than it is consumed, it will accumulate. To discuss these ideas quantitatively, we must first raise two fundamental issues in chemical kinetics. How do we define the rate of the reaction And how can we measure it  

Aside from our interest in the rate of destruction of ozone, we have some general experience with rates. If we travel 55 miles from home and it takes us an hour to go that distance, we say that our average speed is 5 5 miles per hour. 

In this ratio, there is an indication of progress (distance traveled) related to the time required to make that progress. Because the distance measured was from zero miles (at home) to 55 miles from home, the change in distance from home can be symbolized by Ad, where A is the symbol for change. The time changed from zero time (at home) to one hour later at our destination. So the time elapsed can be represented by At. 

How do we translate this ratio into one that is meaningful for chemical reactions  

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