Kinetecs Flashcards
Rate law
Rate=k[A]^n
Rates of chemical change
Change in the concentration of a specific element over a period of time
Units of M per second
See the book for practice
Instantanteous Rate
Limit as (t-initial)+(t-final) approaches the designated time In Δ[elementConcentration]/Δt
First order reactant
The rate varies directly with the concentration of reactant-A, forms a linear curve
Rate=k[A]^1
Second order reactant
The rate of the reaction changes exponentially with a change in the concentration of the A reactant
Rate=k[A]^2
Reaction order for multiples reactants
Rate=k([A]^m)([B]^n)
The order of the individual reactant remains unchanged in the reaction, only the k-value changes (depends on the how many, as well as which, reactants factor into the problem here
Integrated rate Law
The concentrations of the reactants is related to time time
First order integrate rate law
Natrual log [A] as a ratio to its original concentration for the simplest linear function
Ln([A]sub-t)/([A]sub-0)=-k*t
Write it out for practice
Second-order integrated rate law
Describes the reciprocal of the concentration of [A] in terms of ‘t’
Basically just the inverse of the zero-order law
1/([A]sub-t)=-k*t +(1/[A]sub-0)
Zero-order integrated rate law
Describes concentration as a linear function of (t)
[A]sub-t= -k*t +[A]sub-0
Half life of a reaction
T sub-1/2= 0.693/k
Or
T sub-1/2= ([A]sub-0)/2k
Arrhenius Equation
k= Ae^ ((-Ea)/RT)
A=frequency factor, individual to each reaction
Ea=activation energy
R= gas constant
T= temperature in kelvin
Activation energy
Energy that much be accumulated for the reaction to take plac
Activated complex (transition state)
The high energy state all molecules go through to go from reactants to products
Frequency factor (A)
Number of time the reactants approach the activation energy level per minute
Exponential factor
e^(-Ea/RT)
Represents a number 0 through 1 represents the fraction of molecules that have enough energy to participate in the reaction
Arrhenius plot
Linear equation that represents the relationship between the temperature and the ‘k-value’
Ln k=-Ea/R*(1/T) +ln A
Arrhenius Equation (two point form)
Ln (k2/k1)=Ea/R*(1/T1-1/T2)
Collision Model
The reaction in question calls for an energetic collision between two molecules
Orientation factor (p)
Numerical representation of the angle at which the molecules must collide with one another for the reaction to occur
Collision frequency (z)
Number of particle collisions that occur per unit of time
K-value from Collision model
k=pz(exponentialFactor)
Write it out
Reaction mechanism
Series of individual chemical equations by which an overall chemical reaction occurs
Elementary step
The simplest possible step, chemical equation) into which an entire reaction mechanism can always be broken down
Law of elementary steps in reaction mechanisms
An entire reaction mechanism can always be broken down into one simple chemical equation that describes the entire process, known as the elementary step
Reaction intermediate
A molecule formed in an elementary step of a reaction mechanism but broken down by another reaction mechanism’s elementary step
Molecularity
Number of reactant particles involved in a step
Unimolecular reaction
Only one reactant is required
Bimolecular
Two reactants are required
Termolecular
Elementary steps in which three reactant particles collide,
Very rare to occur
Rate-determining step
The slowest step in the reaction mechanism
Activation energy in reaction mechanisms
Each require a little more energy, constant energy must be supplied
Instantanteous Rate
Limit as (t-initial)+(t-final) approaches the designated time In Δ[elementConcentration]/Δt
Reaction order for multiples reactants
Rate=k[A]^m[B]^n
First order integrate rate law
Ln([A]sub-t)/([A]sub-0)=-k*t
Write it out for practice
Second-order integrated rate law
1/([A]sub-t)=-k*t +(1/[A]sub-0)
Zero-order integrated rate law
[A]sub-t= -k*t +[A]sub-0
Half life of a reaction
T sub-1/2= 0.693/k
Or
T sub-1/2= ([A]sub-0)/2k
Arrhenius Equation
k= Ae^ ((-Ea)/RT) Or ln(k)=ln(A)-(Ea/RT)
A=frequency factor, individual to each reaction
Ea=activation energy (in kJ/mol)
R= gas constant
T= temperature in kelvin
Activation energy
Energy that much be accumulated for the reaction to take plac
Activated complex (transition state)
The high energy state all molecules go through to go from reactants to products
Frequency factor (A)
Number of time the reactants approach the activation energy level per minute
Exponential factor
e^(-Ea/RT)
Represents a number 0 through 1 represents the fraction of molecules that have enough energy to participate in the reaction
Arrhenius plot
Linear equation that represents the relationship between the temperature and the ‘k-value’
Ln k=-Ea/R*(1/T) +ln A
Arrhenius Equation (two point form)
Ln (k2/k1)=Ea/R*(1/T1-1/T2)
Collision Model
The reaction in question calls for an energetic collision between two molecules
Orientation factor (p)
Numerical representation of the angle at which the molecules must collide with one another for the reaction to occur
Collision frequency (z)
Number of particle collisions that occur per unit of time
K-value from Collision model
k=pz(exponentialFactor)
Write it out
Reaction mechanism
Series of individual chemical equations by which an overall chemical reaction occurs
Elementary step
The simplest possible step, chemical equation) into which an entire reaction mechanism can always be broken down
Law of elementary steps in reaction mechanisms
An entire reaction mechanism can always be broken down into one simple chemical equation that describes the entire process, known as the elementary step
Reaction intermediate
A molecule formed in an elementary step of a reaction mechanism but broken down by another reaction mechanism’s elementary step
Molecularity
Number of reactant particles involved in a step
Unimolecular reaction
Only one reactant is required
Bimolecular
Two reactants are required
Reaction Order
Power ‘n’ to which the concentration is raised in the rate formula, determines the effect the concentration of that product has on the rate.
The ‘n’ in
Rate=k*[A]^n
Zero order reactant
Rate=k*[A]^0
The rate is independent of the concentration of that particular reactant
Reaction order for a catalyst
Always zero
Overall rates of reaction
Same as the rate of a reactant with a single coefficient
Individual reactant rate
Same as the overall reaction rate multiplied by its coefficient
Reaction rate when coefficient is multiplied
The rate is multiplied by that same value
Approximating reactant order
Graph- value=zeroOrder, linear=firstOrder, exponential=secondOrder
Algebra- [A]^x=OverallRate/k, x-is reactant order
Approximating k-value
k=Rate/[A]^x
When graphing concentration vs time
Use arhennious equations
Catalyst mechanism of action
Lowers the activation energy required for the reaction to take place
Activating energy from the k-value
Ea=[Ln(k)-Ln(A)]*(RT)
Reaction enthalpy ΔH
The net energy change when the reactants are transformed into products
Termolecular
Elementary steps in which three reactant particles collide,
Very rare to occur
Rate-determining step
The slowest step in the reaction mechanism
Activation energy in reaction mechanisms
Each require a little more energy, constant energy must be supplied
