A.P. Exam Review Regular Review Day 4

Big Idea #4 Rates of chemical reactions are determined by details of the molecular collisions.

Enduring Understanding A Reaction rates that depend on temperature and other environmental factors are determined by measuring changes in concentrations of reactants or products over time.

Enduring Understanding B Elementary reactions are mediated by collisions between molecules. Only collisions having sufficient energy and proper relative orientation of reactants lead to products.

Enduring Understanding C Many reactions proceed via a series of elementary reactions.

Enduring Understanding D Reaction rates may be increased by the presence of a catalyst.

= rate = rate constant derived definition: Rate law can be written from molecularity Lowers the E a by making a new ______________ Why? Experimentally derived rate laws show that all reactions aren’t elementary k = zpe -E a /RT k = ln k= Relating [ ] vs. time 1st order: 2nd order: 0 order: Ch. 12 A.P. Chem. Chemical Kinetics Reaction RatesMechanisms -  [ ]  time Avg. Rates Instantaneous Rates Slope of the line tangent at that moment Rate Law k [ ] x experimentally Method of initial rates Constant rates [ ]’s for certain substances high Zero order in one substance Compare runs with all but one [ ] constant Integrated Rate Laws ln[ ] = -kt + ln[ ] 0 1/[ ] = kt + 1/[ ] 0 [ ] = -kt +[ ] 0 ln([ ]/[ ] 0 ) = -kt 0.693/k 1/k[ ] 0 [ ] 0 /2k t½t½ series of steps by which a reaction occurs Elementary steps Inter- mediates RDS catalysts mechanism: Used in one step, produced in another Produced in one step, used in another with a new and faster (dictates) Speeds up a reaction without being consumed collision theory Effective collisions enough energy Break and make new bonds transitional particle activated complex...seen on P.E. diagram Proper orientation Ae -E a /RT (-E a /R)1/T + lnA Arrhenius Equation(s) order

Beta Radiation Electron Capture Alpha Radiation ________