CHEM 134 Lecture Notes - Lecture 26: Gas Constant, Ozone Depletion, Molecularity

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For second-order reactions , the mathematical form of the integrated rate law is quite different from the one we used for first-order reactions. The half-life of a reactant is the time it takes for its concentration to fall to one-half its original value. Although this quantity can be defined for any reaction, it is particularly meaningful for first-order reactions. Because does not depend on the amount of substance present, neither does . The half-life is most often used to describe the kinetics of nuclear decay. All radioactive decay processes follow first-order kinetics, and people working with nuclear processes typically use half-lives. The kinetic-molecular theory says that molecules interact with one another only through collisions. So, for two molecules to react, first they must collide. We should not expect that all collisions between molecules result in chemical reactions, though. Our experience suggests that the air surrounding us is stable, even though the and molecules are constantly colliding.