CHEM 122 11th Edition Lecture 17Outline of Last LectureI. Simple First Order Reaction Rate Lawa. Half life of first orderII. Simple Second-Order Reactionsa. Half life of second orderOutline of Current Lecture I. Collision Theory ModelII. Effect of Temperature on RateIII.Current LectureCollision Theory model: Rate of a reaction is proportional to the number of effective collisions per second- Effective collision: A collision that results in the formation of productso only a very small number of collisions actually result in an effective collision.- What is required for a reaction to occur?1. Molecules must collide2. The energy of the collision must exceed some minimum energy3. They must collide in the proper orientation (head on, from the side etc)- When concentration is increased, so is the number of collisions.Effect of Temperature on Rate:- Temperature effects the rate constant (k) as temperature increases.- General Rule: the rate constant for a reaction increases by about a factor of 2 to 3 for each 10 degrees celcius increase in temperature.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best Used as a supplement to your own notes, not as a substitute.- Why is there this strong temperature dependence on the rate constant of a reaction?o As temperature increases, molecules move faster, therefore, there are more collisions per second.o But the increased collision frequency doesn’t account for the dramatic temperature effect on rate constants.- For molecules to react, the energy of the collision must be greater then the minimum energy.- The kenetic energy of the colliding molecules that supplies the energy for the reaction tooccur, changes into potential energy when molecules collide.- Activiation energy: minimum
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