chemistry: chemical kinetics

thermodynamics

determines whether a reaction will proceed forward spontaneously or not

kinetics

how fast the reaction will proceed in the forward direction

reaction rate

speed of a chemical reaction

reaction rate equation

delta x/delta t

factors affecting reaction rate

temperature, concentration, catalyst, pressure, nature of reactants, reaction mechanism

average rate of the reaction

change in concentration/change in time

instantaneous rate

rate at a specific moment in time; slope of concentration vs time graph at a particular point

as time goes on, what happens to the rate of a reaction and why?

it decreases because the concentration of reactants decreases

why does the reaction eventually stop?

the reactants ran out or the system has reached equilibrium

rate law

relationship between the rate of the reaction and the concentration; related by k

n/m exponent

order of the reaction

overall reaction order

sum of the order exponents

1st order integrated rate law

ln[A]t = ln[A]0 - kt

2nd order integrated rate law

1/[A]t = 1/[A]0 + kt

zero order integrated rate law

[A]t = [A]0 - kt

half life

time it takes for the original concentration to decrease by half

1st order half life

t1/2 = 0.693/k

2nd order half life

t1/2 = 1/k[A]0

zero order half life

t1/2= [A]0/2K

k1

rate constant of forward reaction

k-1

rate constant of reverse reaction

K>1 —> k1 and k-1?

more P than R; k1 > k-1

K<1 —> k1 and k-1?

more R than P; k1 < k-1

elementary step

each step in a reaction

molecularity

number of reactant molecules that form a product

unimoleculer

process involving one reactant

bimolecular

process involving two reactants

termolecular

process involving three reactants

arrhenius equation

lnk = -Ea/RT + lnA

Ea (activation energy)

minimum energy needed to start a reaction

activated complex

combination of molecules that can either produce products or fall apart

collision theory

for a reaction to take place, the reacting molecules must collide with each other

frequency factor

number of molecules that begin to form an activated complex in time

exponential factor (e^-Ea/RT)

fraction of reactant molecules with sufficient energy that can make it over the energy barrier

catalyst

substance that speeds up the rate of a reaction by lowering activation energy

homogenous catalyst

reactants and catalysts are in the same phase

heterogenous catalyst

reactants and catalysts are in different phases