CHEM 122 1st Edition Lecture 18Outline of Last LectureI. Collision Theory ModelII. Effect of Temperature on RateOutline of Current Lecture I. Activation Energya. Forward and reverseII. Svante Arrheniusa. Arrhenius equationb. Frequency factorc. Straight line equationIII. Fraction of collision EquationCurrent LectureActivation Energy- The relationship between Ea (activation energy) forward and reverse reactions: Ea(forward)−∆ H=Ea(reverse) o Remember ∆ H is negative when the reaction is exothermic.- Why does temperature have a significant effect on rate constants and reaction rates?o Only collisions whose kinetic energy exceeds activation energy can react, and only a very small fraction of collisions actually exceed the activation energy.Svante Arrhenius: Chemist in the late 1800’s who studied the effect of temperature on the reaction rates.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.- Arrhenius equation: k =A e−EaRT o K: rate constantoEa: Activation energyoR: Gas constant (8.314J/mol K)oT : Absolute temperature (kelvin)oA : Frequency factor The frequency factor takes into account both the collision rate as well as the probability that the collisions have the proper orientation.- As Ea increases, k increases- As T increases, k increases- The Arrhenius equation can be rearranged to the equation of a straight line (y=mx+b)olnk=(−EaR)1T+lnAo A plot of ln k and 1/T yields a straight line- Fraction of collisions whose collision energy exceeds activation
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