Chem Exam II
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When determining and using initial rate laws there is
-require experiemntal data
-you are able to calculate reaction orders and calculate the value of the rate law
The integrate rate law does what?
-relates concentration to time
First order reaction rate law?
First order integrated rate law?
as a linear equation
Time require to concentration of the reactiant to be reduced by one half its original concentration.
First order reaction half life equation?
-for first order reactions the half-life is
of the initial concentration
Second order reaction rate law?
Second order integrated rate law
as a linear equation
Second order reaction half-life equation?
in the second order reation t
the intitial concentration.
If the temperature increases...
Rate increases and
To react, reactants must encounter eachother
If we increase the number of successful collisions you...
increase the rate
If you increase the reactant concentration....
you increase the number of collisions
Succesful collisions require:
1. collision must have sufficient energy
2. collision must have reactants in the proper orientation
Activation enegy is?
Energy barrier between the reactants and the products.
Activation energy graph
The transition state is
where the intermediate is created and destroyed between the reactants and products
also called the activated complex
What determines if the reactnat have sufficient E to form the transistion state
Energy (K.E.) of the reactant relative to the activation energy
-increase speed of K.E.
- lower the size of the barrier
Frequency equation is
If the frequency increases two things have happened
the temperature as been increased
the activation energy has decreased
not all collisions with the K.E. higher than the E
with result in a trantisition state formation.
Bad collisions are caused from what and how the molecule is made.
Arrhenius equation is
A is the frequency factor and it is
specific to each reaction
depends on reactant geometry
is independant of temperature
Uses of Arrhenius Equation
Graphical determination of E
Determining k at various temperatures ln(k
When solving for either k make sure it is in the k
Reaction Mechanisms: Elementary steps
describe the actual interactions between reactants at the molecular level
descirve overall reactions as a series of steps;
describe an actual collision
explains rate laws
classification of elementary steps based on the number of reactnatn in the collision
Molecularity and Rate law
for an elementary step; molecularity determines the rate law for one step at a time
Molecularity determines the reaction order unimolecular rate law is
Molecularity determines the reaction order bimolecular rate law is
What is the rate determining step?
a specal step in a mechanism
slowest step in a mechanism
determines the rate of the overal reaction
The rate law for the slowest step is what?
the rate law for the overall reaction
if the reaction occurs in one step the rate law correstongd to the overall reaction
Determining reaction mechanisms by four steps
1. based on experiemtnally determined rate law
2. mechanisms consist only of elementary steps- plausible collisions
3. one steop is rate determining-determines the overall rate law
4. The sum of steps=the overall reaction
Hints about reaction mechanisms
mechanisms tent to occur in a minimal amount of steps
reactions with a low overall reaction order (1 or 2) the initial step is usually the slowest
reactions with a fast initial step often have higher (3) overall reaction orders
reaction intermediates are usually in the slow reaction step(s)
a substance that decreases E
, increases A in the Arrhenius equation
Homogenous catalyst is?
the catalyst and reactants are in the same phase
heterogenous catalyst is?
reactants and catalyst are in different phases
A catalyst is a reaction does what to the mechanism?
by changing the transition state
changes the reaction mechanism
forms lower energy transition state
Heterogenous cataysis usually happens by surface catalyzing
: binding at the surface)
: of the adsorbed reactants
3. reaction at surface
: products are relaeased from binding at catalyst surface
speed up a reaction
Protein structures based off of primary structure and secondary and teritary structure the shape dictates the function and activity of the protein
primary structure-amino acid sequence
secondary and tertiary structure- define the overall shape of the protein, maintained by the amino acid interactions
Enzyme mechanism process is a lock and key model
1. reacnant substrate bind to the enzyme at the active sight
2. forms enzyme sybstrate complez
3. products are released
Enzyme activity can be disruped by enzyme inhibitors by
1. binding to the active site
2. distoring the enzyme structure
what is Dynamic equilibrium?
when forard and reverse reactions both occur at the same rate
both reactants and products are presents in a
but seldom equal amounts
The product reaction ratio depends on
theormodynamics of the reaction
: temperature influence and pressure influence
establishing equilibrium means that
systems shift form initial conditions to establish the equilibrium ratio of the products to reactnat set by the reaction theromodynamics and the reactions conditions
equilibrium of gases is K
The relationship equation between K
change in n
evaluating equilibrium constants
all k's are rations of prod/reactant
if product is >reactant and if reactant is > product
where does the equilibrium lie?
Product > reactant it lies to the right
reactant > product it lies to the left
Heterogenous equilibrium when reactants and products are in multiple phases what phases
in k expressions?
solids and liquids
Chem Exam II
Rate and Equilibrium