Unformatted text preview: of data to see if slope changes for each reaction order. COLLISION MODEL/THEORY: reactant molecules must collide to react Activation Energy (Ea): minimum energy needed for chemical reaction Reaction Rate and Temperature – As T, reaction rate since molecules move faster and more molecules have activation energy. Three Factors Affecting Reaction Rate 1. Concentration 2. Orientation of molecules 3. Temperature and Kinetic Energy – Molecules move faster at higher temps – Molecules must have activation energy (Ea) to react – Molecules must vibrate strongly enough and collide with enough force to make and break bonds
page 1 of 4 CHAPTER 15: Chemical Kinetics (Continued) TRANSITION STATE MODEL Reaction Energy Profiles – Indicate the transition state, activation energy (Ea) for reactants and products, H for a reaction given a reaction energy profile – Distinguish between the activated complex and the transition state – Determine if a reaction is endothermic or exothermic – Given a reaction energy profile for a multi‐
step mechanism, determine the rate‐
determining step based on largest Ea Catalyst: substance added to a system that lowers the activation energy of a reaction. – Know catalysts provide an alternative pathway that eases the collision geometry requirement Recognize that catalysts increase reaction rate without being consumed in reaction – Know homogeneous versus heterogeneous catalysts – Enzymes: catalysts with unique active sites that speed up biochemical reactions Arrhenius Equation: k = A e–Ea/RT where A=frequency factor, Ea=activation energy, R=8.3145 J/mol∙K, T=temperature in K – Know that A reflects the collision geometry requirement – Know how temperature affects k – Be able to solve for any variable given the other variables and/or graphical data Two‐Point Equation of Arrhenius Equation: – Solve for the rate constants or activation energy at two different temperatures k E ln 2 a 1 1 k 1 R T1 T2 Reaction Mechanisms – sequence of steps by which a reaction occurs at the molecular level – The slowest step in a mechanism is the rate‐
determining step – Given the reaction mechanism for a reaction, determine the rate law – If a fast step is followed by a slow step, express the rate law with respect to only the reactants (excluding intermediates) – Giv...
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This document was uploaded on 03/22/2014 for the course CHEM 162 at Seattle Central Community College.
- Fall '11