Collision Theory
Used to predict the rates of reactions and is based upon the idea that molecules must collide with enough kinetic energy and the correct 3D orientation in order to react and form bonds
The higher frequency of collins, the faster the reaction rate
Activation Energy (Ea)
The minimum amount of energy required for a reaction to commence
Energy between the reactant and the transition state
Ea is always POSITIVE
Exothermic
- Reactant > Product
- Delta H is always negative
- Process gives off heat
- “EXIT”
Endothermic
- Energy of products > reactants
- Delta H is positive
- Process consumes heat
- “ENTER”
Transition state
Maximum energy, aka activated complex
Rate
- A rate of change will always be negative for any reactant since reactants are consumed over time
- The larger a reactant or product’s stiometric, the greater the rate of change of its concentration
- The larger the stoichiometric coefficient, the faster the rate of change of a reactant or product concentrations
Rate Laws
- The higher the frequency of molecular collisions, the faster the rate reaction
- The higher the pressure, the higher frequency of molecular collisions=the faster the rate of reaction
- Reaction rate is directly proportional to reactant concentration
- Depends on the rate of REACTANT (not product)
- K is the rate constant, always a positive value
- X and Y are the reaction orders
- The sum of individual reaction orders equals the overall order of the reaction
- Order include: Zero, first, second, third
Rate Constant
0 order units of k = M+^1 x s^-1
1 order units of k = s^-1
2 order units of k = M+^-1 x s^-1
3 order units of k = M+^-2 x s^-1
Arrhenius equation
A= frequency factor E=activation energy R=ideal gas constant= 8.314 J/ mol K K=rate constant T=temp
The concentration of reactant changes …
The concentration of reactant changes changes the reaction rate, but not the rate constant
A catalyst results in a large
rate constant K
An increase in temperature almost always
Increases K
