Ch. 15 Kinetics Flashcards
What are Kinetics?
A study of reaction rates, and the relation to the way a reaction proceeds.
What are reaction rates?
the change in concentration of a reactant/product over time!
What are the 3 types of reaction rates:
Initial Rate, Average Rate, and Instantaneous Rate (the rxn rate at any 1 point in time) we use Initial a lot!
What is the Integrated Rate Law? What is it used for?
It is the relationship between concentration and time. You can use the Integrated Rate Laws in the form of y=mx+b, where K would be the slope (m) of the eqn.
What are some factors that affect the reaction rate of a rxn?
- Concentrations!!!
- Temperature
- Catalysts!!!
- Mixing the Reactants
How are reaction rates found/defined?
for a rxn: aA—>bB
Rate= -1/a Δ[A]/Δt = +1/b Δ[B]/Δt etc.
What is the Rate Law? What does the k and the n and m represent?
Rate=k[A]^m[B]^n where m and n are the rxn order. k is the rate constant of the rxn.
what does each rate order represent?
(based on Rate=k[A]^n)
IF n=0, rxn is zero order, rate is independent of the concentration of A.
IF m=1, rxn is 1st order, rate is directly proportional to concentration of A.
IF m=2, rxn is 2nd order with respect to THAT reactant. So if [A] doubles, rate increases by 4, etc.
What are the Integrated Rate Laws for each rxn order? What do these equations resemble?
On Paper!
Both 0 Order and 1st Order are in the slope intercept form (y=mx+b)!!!
What is a Half Life? Equations on paper.
The time it takes for a concentration of a reactant to fall to 1/2 its original value.
What is the Collision Theory?
Molecules need to come in contact with eachother for a rxn to take place.
What is the Activation Energy? (Ea)
The energy required for the reactants to reach an activated complex; be able to get over the ‘hump’ and complete a rxn.
What does the height of the Activation Energy signify?
The higher the Activation Energy, the slower the reaction rate.
What does the Arrhenius Equation represent? How can you rearrange it to be more useful? Eqn’s on paper.
The relationship between the Rate Constant (K) and Temperature (also K, kelvins). Equation can be rearranged to be slope intercept!
What are Reaction Mechanisms? Elementary Steps?
Series of individual chemical steps in which the overall reaction occurs. These are called the Elementary Steps (cannot be broken down into further steps)
What is Molecularity? What are the types of molecularity?
The number of reactant particles involved in that step.
Unimolecular: A—>Product
Bimolecular: A+B—>Product
Termolecular: A+2B—>Product
What is the Rate Order of each Molecularity?
Unimolecular: A—>Product, 1st Order
Bimolecular: A+B—>Product, 2nd Order
Termolecular: A+2B—>Product, 3rd Order
What is the Rate-Determining Step?
The slowest step of the reaction; defines the order of the reaction!
When is a Mechanism feasible?
- When the sum of the elementary steps is stoichiometrically consistent with the overall reaction. (Similar to Hess’ Law)
- Order of the rxn is consistent with the order derived from the rate-determining step.
What is a Catalyst? What do they do?
A substance that increases the rate of a chemical rxn. Catalysts are NOT consumed by the rxn. Works by providing an alternate mechanism for rxn.
What are the 2 types of Catalysts?
Homogeneous Catalyst- same phase (or state) as the reactants.
Heterogeneous Catalyst- Different phase (state), usually solid.
