Reaction Mechanisms Flashcards
1
Q
Reaction Mechanism
A
Step by step sequence of elementary reactions by which an overall chemical reaction occurs
2
Q
Elementary Steps
A
Each small step in the mechanism
3
Q
Reaction Intermediate
A
- Produced in an elementary reaction
- Do not appear in the overall chemical reaction or rate law
- Short lived
4
Q
Rate Determining Step
A
The slowest step in the reaction
5
Q
How reaction intermediates work
A
They must be produced by one elementary reaction and then consumed by another
6
Q
How is rate law determined?
A
- Based on the slowest step
- Should be the same as the one determined experimentally
7
Q
A plausible reaction mechanism must be consistent with…
A
- Stoichiometry of the overall reaction
- Experimentally determined rate law
8
Q
What is molecularity?
A
- Describes the number of molecules that must collide for a reaction to occur
- Equal to the sum of stoichiometric coefficients of reactants in the elementary reaction
- Only for elementary steps
9
Q
Elementary steps are either…
A
- Unimolecular
- Bimolecular
- Termolecular
10
Q
Unimolecular
A
- A single molecule dissociates
- A –> Products
11
Q
Bimolecular
A
- Two molecules collide
- Most common
12
Q
Bimolecular examples
A
- 2A –> Products
- A + B –> Products
13
Q
Termolecular
A
- Simultaneous collision of 3 molecules
- Rare
14
Q
Termolecular examples
A
- 3A –> Products
- 2A + B –> Products
- A + B + C –> Products
15
Q
Catalyst
A
Any species present at the beginning as a reactant and a product at the end
