Chapter 15 - Chemical Kinetics

Question 1

Explain the two rate laws

Answer 1

Differential rate law: describes the rate as a function of concentration
Integrated rate law: describes the concentration as a function of time

Question 2

What is a reaction mechanism?

Answer 2

Series of elementary steps by which an overall reaction occurs

Question 3

What are the two requirements for an appropriate mechanism?

Answer 3

The elementary steps sum to give the correct overall balanced equation
The mechanism agrees with the experimentally determined rate law

Question 4

What is the rate limiting step?

Answer 4

Slowest elementary step; determines the rate of the reaction

Question 5

What is steady rate approximation?

Answer 5

Used when a specific rate-determining step cannot be chosen.
Assumes the concentration of any intermediate remains constant as the
reaction proceeds.

Question 6

Describe the collision model

Answer 6

The simplest model to account for reaction kinetics is the collision model
n Molecules must collide to react
n The collision kinetic energy furnishes the potential energy needed to
enable the reactants to rearrange to form products
n A certain threshold energy called the activation energy (Ea) is necessary
for a reaction to occur
n The relative orientations of the colliding reactants are also a determining
factor in the reaction rate

Question 7

Describe what a catalyst is and give the two types.

Answer 7

Speeds up a reaction without being consumed
Works by providing a lower-energy pathway for the reaction
Enzymes are biological catalysts
Catalysts can be classified as homogeneous or heterogeneous
n Homogeneous: exist in the same phase as the reactants
n Heterogeneous: exist in a different phase than the reactants