Chemical Kinetics (5) Flashcards
Rate determining step
slowest step, limits the maximum rate at which the reaction can proceed.
Collision theory
states that a reaction rate is proportional to the number of effective collisions between the reacting molecules.
- For a collision to be effective, molecules must be in the proper orientation and have sufficient kenetic energy to exceed activation energy.
- Arrhenius equation is a mathematical way of representing collision theory
Arrhenius equation
higher temperature and lower activation energy will result in increase rate constant.
Exergonic rxn
- ΔG and energy is given off.
Endergonic rxn
+ ΔG and energy is abosorbed.
Catalyst
Catalyst: increases reaction rate by lowering activation energy.
Homogeneous catalysis
catalyst is in the same phase (solid, liquid, and gas) as the reactant.
Heterogeneous catalysis
catalyst is in a different phase than the reactant.
Transition state theory
states that molecules form a transition state during an rxn in which old bonds are partially dissociated and the new bonds are partially formed.
Free energy change of the reaction (Delta G)
Free energy of product - Free energy of the reactant
Factor affecting reaction rate
Rate concentration: the greater the concentration of the reactants, the greater the number of effective Collison per uni time.
Temperature: Reaction rate increases as temperature increases.
Medium: the rate at which an rxn takes place may also be affected by the medium in which it takes place.
Catalyst: increases reaction rate by decreasing activation energy.
Zero-order reaction
rate = [A]^0 [B]^0
rate = k
units of k = M/s
-Lower the Ea which will increase the value of k
First-order reaction
rate = k [A] ^1
ln[A] vs time graph
unit of k = 1/s
k = -slope
Radioactive decay
[A]t = [A]initial x e^ -kt
first-order rxn
Second-order reaction
rate = k[A]^1 {B]^1 or rate = k[A]^2
unit of k = 1 / M s
1/[A] vs time graph
k = +slope
