AP Chem Unit 5

chemical kinetics

the area of chemistry that models reaction rates and why they diff

reaction rate

change in concentration/ change in time= rate

rate=

K\[A\]^n

rate

(mol/L(sec)

k

reaction constant

A

concentration of reaction

n

order of reactant, has to be determined experimentally

0 order

change is concertation, doesn’t affect reaction rate

1st order

prop change, double concertation, rate doubles

2nd order

exponential, double concentration, rate 4x

differential rate laws

concentration and rate data

integrated rate law

concentration and time data

integrated first order rate law

Ln\[A\]=-kt+Ln\[A\]o

integrated second order rate law

1/\[A\]=kt+1/\[A\]o

reaction mechanisms

series of proposal steps

integrated zero order rate law

\-kt+\[A\]o

intermediates

substances produced in 1 step and consumed in another

elementary steps

a step in a reaction mechanism

molecularity

\# of a species much react to cause a reaction

rate determining step

slowest step, write rate law based on the slowest step

collision model (critical for success)

activation energy, orientation

activation energy (Ea)

min amount of energy required in a collision for a reaction to occur

relationship of Ea

higher Ea means the reaction will go slower, few collisions will have the energy needed to overcome Ea

slowest has the highest Ea

catalyst

speeds up a reaction without being consumed

effects of catalyst

creates a new pathway

lowers activation energy

this results in a greater # of effective collisions

heterogeneous catalysts

pressed in a different phase

homogeneous catalysts

exists in the same phase- usually a solid