kinetics Flashcards
Change in free energy
delta H
activation energy
Ea
y axis for boltzmann distribution curve
of particles
x axis boltzmann distribution curve
kinetic energy (speed)
threshold for having enough energy to react
activation energy
influence of temperature on rate
Increase temp increase rate
influence of concentration on rate
increase concentration increase rate
general rate of reaction
also called avg rate, specific for given time interval, secant line (two points) written rate= -delta[A]/t (negative sign represents that A is disappearing)
instantaneous rate
at specifically defined conditions, often initial rate, tangent line, instantaneous rate = -d[A]/dt when d=infantesimally small delta (change)
units for first order k
t^-1
units for second order k
m^-1t^-1
units for third order k
m^-2t^-1
how can we determine order of reaction
using units for k
what is k
a proportionality constant (number with units) that relates rate to concentration
order if concentration doubles and rate doubles
first order reaction
zero order impact on rate
zero order does not impact rate
half-life equation zero order rxn
[A]0/2k
is half-life equation for zero order rxn dependent on initial concentration?
yes, [A]0/2k (includes [A]0)
is half-life equation for first order rxn dependent on initial concentration?
no, ln2/k does not include [A]0
is half-life equation for second order rxn dependent on initial concentration?
yes, 1/k[A]0 (includes [A]0)
half-life equation first order rxn
ln2/K
half-life equation second order rxn
1/k[A]0
as rate constant (k) increases, half life
decreases (for any rxn order)
for zero order rxn, increase initial concentration, half life
increases
for second order rxn, increase initial concentration, half life
decreases
for first order rxn, increase initial concentration, half life
does not change, independent
integrated rate law zero order in form y=mx+b
[A]f= -kt+[A]0, slope= -k, y-int =[A]0
integrated rate law first order in form y=mx+b
ln[A]f= -kt+ln[A]0, slope= -k, y-int= ln[A]0
integrated rate law second order in form y=mx+b
1/[A]f= kt+1/[A]0, slope= +k, y-int= 1/[A]0
zero order plot that leads to straight line graph
[A] vs t
first order plot that leads to straight line graph
ln[A] vs t
second order plot that leads to straight line graph
1/[A] vs t
which rate law is represented by the experimental rate law
the first (slow) step
as [R] decreases, forward reaction rate
decreases
as [P] increases, reverse rate
increases
k1/k-1 = [P]/[R]
Keq
how to write rate law for system of elementary rxns for appearance of product
start with the step where F is made
how to write rate law for system of elementary rxns for overall rxn
start with final step
steady state approximation
assumes the rate of appearance of C= rate of dissapearance of C
