Kinetics Flashcards
an average rate is defined over
some time window
RATE =
change in concentration / change in time
Mole rates are related. what is the relationship like
they are porportionate. balanced equation will increase moles proportionally
Rates can change, how?
The rate of production can increase or decrease, check slope steepness. If slope is steep, rate is fast. If slope less steep, rate slowed down.
Rate law
equation showing how reaction rate depends on concentration of each reactant
if aA+bB –> cC + dD, rate =
k [A]^m [B} ^n
k = rate constant
m = reaction order in A
n = reaction order in B
reaction rate describes
how fast reaction is going
rate laws
show how the reate depedns on the reactant concentrations
half-life
time it takes to react 50%
arrhenius equation describes
how rate constant changes with TEMPERATURE
Reaction mechanisms
-connect microscopic molecular processes to overall rate
-reveal how reaction occurs
Intergrated rate laws describe
mathematical functions give concentrations through time
Method of initial rates: granular
- Two expirments vary
- divide inital [B] values with ^n to get n ( rate3/rate2 = [B3}^n / [B2] ^n]
- divide inital [A] values with ^m to get m (9 = 3 ^m)
- use data on any one expiriment and plug in for according rate law
rate laws:
rate = k[A]⁰ = k
rate = k[A]
rate = k[A][B]
rate = k[A]²[B]
Order and units:
0. M/s
1. 1/s
2. 1/(M s)
3. 1/m^2 s)
Zero Order Integrated law
[A]t = -kt + [A]₀
[A]₀ is inital conc.
[A]ₜ is concentration at t
STEEP linearly DECREASE slope
half life zero order
t₀.₅ = [A]₀ / 2k
First order intergraded
[A]ₜ = [A]₀e⁻ᵏᵗ
or
ln [A]ₜ/[A]₀ = -kt
-linearly decrease slope
Second order integrated
1/[A]ₜ = kt + 1/[A]₀
[A]₀ = initial conc
[A]ₜ = conc at time
-linear INCREASE slope
half life first order
t₀.₅ = ln(2)/k
half life second order
t₀.₅ = 1/k[A]₀
conc vs time zero
straight down then flat
conc vs time first
smooth curve down
conc vs time second
broken curve down
Elemtary reaction
individual molecular event
overall reaction
reaction stoichiometry
reaction intermediate
species formed in one step and consumed in another
catalyst
if consumed in first then regenerated
ther rate law for an elementary reaction only follows directly from its molecularity because
An elementary reaction is an individual molecular collision
determine fast step and slow step
- fast is at equilibrium
- slow is not
net reaction
add all elements that cant be cancelled up
collisions happen all the time but only some causes _____________________
an event to happen
reactants must ______ with correct _________
collide, orientation
- 0 < p ≤ 1 YUP
- p for simple molecules:
- p for large molecules:
- IF reaction isnt sensitive to orientation
P for simple: 0.001-1
P for large: < 10⁻⁵
not sensitive: p = 1
Collision theory: For a biomolecular reaction to take place, reactants A and B must _______ with __________ __________, and an energy greater than the _______ ________
collide, proper orientation, activation energy
in collision theory,
rate = k[A][B] –> k = Zpf where Zpf means
Z = volumetric collision freq (INCREASES with T)
p = fraction with correct orientation (NO CHANGE with T)
f = fraction with sufficient energy (INCREASES with T)
Transition State: The ________ _____ of atoms that are ________________ along the pathway from reactants to products
Unstable group, highest energy
Activation energy
Minimum energy reauired for successful reaction
As T ________, fractions of collisions with _________ ________ react to increases exponentially.
Increases, sufficient energy
As T increases, fractions of collisions with sufficient energy react to increases exponentially. Higher T –>
BIGGER SPIKE on graph at beggining, ends up lower
–> smaller Ea
–> LARGER eˣ
–> LArger reciprocal
—> larger f & k
–> increased rate
Arrhenious equation
k = Ae⁻ᴱᵃ/ᴿᵗ or lnk = -Ea/R (1/T) + lnA
Arrhenius plot faciliates graphical determination of the ________ ______ ( which is the slope)
activation energy (lnk vs 1/T)
what order reaction are enzymes at low substrate concentration and high substrate concentration
LOW: First-order behaviour - rate increases linearly with S
HIGH: Zeroth-order, once all enzyme is complexed, rate of reaction saturates.
