y2 rates Flashcards
zero order
rate = [A]^0
concentration of reactant has no effect on rate
first order
rate=[A]^1
concentration of reactant directly proportional to rate
if conc doubled then rate doubles
second order
rate= [A]^2
if conc x3, rate increases by 9 (3^2)
rate equation
rate= k[A]^m[B]^n
only includes species involved in RDS
overall order of reaction
sum of orders in respect to each reactant
half life def
time taken for half volume/ mass of reactant to be used up
first order half life
constant half lives
exponential decay
confirmed by measuring successive half lives on graph
k using half life
ln2/t1/2
first order only
rate/conc graph 0 order
k= y intercept
straight, horizontal line
rate/ conc graph 1 order
straight line with constant gradient
k= gradient
rate/ conc graph 2 order
second graph drawn
rate/ (conc)^2
straight line produced
gradient of line =k
RDS
slowest step in sequence in multi, step reaction
species involved in RDS are used in rate equation
rate eq and RDS
only species involved in RDS will be in rate eq
orders in rate eq match no of species involved in rate eq
effect of temp on rds
as temp increases, rate increases and value of K increases
increased temp increases proportion of particles that exceed Ea
- causes particles to move faster and have more frequent successful collisions
arrhenius eq
k= A e^ (-Ea/ RT)
R= gas constant= 8.314 Jmol^-1K^-1
T= temp in kelvin
Arr eq exponential factor
proportion of molecules that exceed Ea and have sufficient energy for a reaction
A arr eq
frequency factor
takes into account frequency of collisions with correct orientation
shows rate if there was no Ea
log form arr eq
ln k= -Ea / RT + lnA
graph lnK
plot ln K against 1/T
shows graph form y=mx+c
-Ea/ RT = m
1/T = x
lnA=c
