Lecture 9-10 (Ch. 14): Collision Theory, Arrhenius Equation, Mechanisms, Catalysts Flashcards
1
Q
collision theory
A
- molecules must collide for a rxn occur (more collisions = faster rates)
- colliding molecules must be orientated properly to react
- properly oriented molecules must have sufficient energy
2
Q
activation energy (Ea)
A
- minimum energy required to break bonds
- more important than orientation
- units: kg/mol
3
Q
enthalpy (ΔHrxn)
A
-difference btwn reactants & products
4
Q
how does activation energy impact the rate?
A
-the smaller the Ea, the faster the rxn
5
Q
what is the arrhenius equation?
A
k=Ae^(-Ea/RT) or ln(k2/k1)=Ea/R(1/T1-1/T2) R: 8.314 A: frequency factor
6
Q
elementary step rxns
A
- a 1 step event
- a single collision of correctly orientated & energetic rxns
7
Q
molecularity
A
-describes the # of molecules on the rxt side of an elementary chemical rxn
8
Q
unimolecular rxn
A
-1 reactant in rate law
9
Q
bimolecular rxn
A
-2 reactants in rate law
10
Q
termolecular rxn
A
-3 reactants in rate law
11
Q
multistep rxns
A
- overall chemical rxn occurs in a sequence of separate steps (more than 1 collision)
- each step is an elementary rxn and must add all steps to get overall rxn
12
Q
what is the importance of the slow step?
A
-it’s the rate determining step
13
Q
intermediate
A
-substance formed in one step and then consumed in another
14
Q
do you add the intermediate in rate law?
A
-no because it has a low concentration
15
Q
catalysts
A
- a chemical that changes the rxn rate w/o being consumed during a rxn
- used in one step & regenerated
- inc. rxn rate by increasing k and lowering activation energy (Ea)
