Ch. 5: Chemical Kinetics Flashcards
What is the relationship between the variables in the Arrhenius equation?
Arrhenius Equation: k=Ae^(-Ea/RT)
k is the rate constant
As T ↑ k ↑
As Ea ↑ k ↓
What does the variable A in the Arrhenius equation represent? How does it change?
A is the frequency factor of collisions. It is increased by increasing the concentration of molecules, which increases the number of collisions.
What are four factors that affect reaction rate?
Reaction concentrations
Temperature
Medium of reaction
Catalysts
Increasing the reaction concentration increases the reaction rate for all EXCEPT what type of reaction?
Zero-order reactions because their rate does not depend on the concentration of reactants.
Why does increasing temperature increase reaction rate?
As temperature increases, the average kinetic energy of molecules increases. Therefore, reactants gain more energy to surpass Ea.
What is the difference between homogenous and heterogeneous catalysis?
Homogenous catalysis: catalyst is in the same phase (solid, liquid, gas) as reactants.
Heterogenous catalysis: catalyst is in a different phase compared to reactants.
What is the rate law of a zero-order reaction?
rate = k
The rate of formation of the product is INDEPENDENT of changes in concentration of reactions.
What are the units of k in a zero-order reaction?
M/s
What factors change the rate of a zero-order reaction?
Temperature
Catalyst: lowers Ea and increases k
What is the concentration vs time equation of a zero-order reaction? What does this look like on a graph?
[A] = [A]o - kt
Graph: negative linear with slope = -k
What is the rate law of a first-order reaction?
rate = k[A]^1
The rate is directly proportional to only ONE reactant.
What are the units of k in a first-order reaction?
1/s = s^-1
What is a classic example of a first-order reaction?
Radioactive decay — the reactant undergoes a chemical change all by itself, without chemical or physical interaction with another molecule
What is the integrated rate law of first-order reaction? what does the graph look like?
[A] = [A]o e^(kt)
ln [A] = ln[A]o - kt
The graph of ln [A] = ln[A]o - kt is negative linear with a slope = -k
What is the rate law of a second-order reaction?
rate = k[A]^2 or rate = k[B]^2 or rate = k[A]^1 [B]^1
