AP Chemistry : Principles of Reaction Kinetics
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Example Question #1 : Principles Of Reaction Kinetics
The overall reaction can only proceed as quickly as the __________.
rate-determining step
products are removed
catalyst is added
intermediate is decomposed
rate-determining step
The rate-determining step in a reaction mechanism is a kinetic bottleneck, in that it prevents the overall reaction from proceeding; thus, it is what determines how quickly the overall reaction can proceed.
Example Question #1 : Principles Of Reaction Kinetics
Which of the following does not affect a forward reaction rate?
Temperature
Catalysts
Product concentration
Medium
Product concentration
Product concentration would not affect a forward reaction rate, since that is what is being formed. Catalysts specifically speed up reaction rates, as does temperature. Medium can also affect reaction rate because some molecules are more likely to react with each other in certain environments.
Example Question #2 : Principles Of Reaction Kinetics
Which of the following is not true of the transition state?
It has a greater energy than the products
It has a greater energy than the reactants
Old bonds are weakened and new bonds begin to form
It cannot dissociate into products without needing any additional energy
It cannot dissociate into products without needing any additional energy
The transition state is the energy barrier in a reaction—energy is needed to reach this state. Once it is acheived, however, it can either revert back to reactants or dissociate into products without any added energy.
Example Question #3 : Principles Of Reaction Kinetics
Which of the following is true:
I. First order reactions proceed at a constant rate
II. First order reactions have a constant half-life
III. First order reactions have one reactant
II only
II and III
I, II, and III
I only
II only
First order reactions have the rate equation 
The half-life equation is 
Lastly, the overall reaction can have any number of reactants. A reaction is first order because its rate-limiting step has only one reactant.
Only statement II is true.
Example Question #4 : Principles Of Reaction Kinetics
The following reversible reaction takes place in a closed container:
The system is allowed to reach equilibrium before 2 moles of reactant A are added to the container.
The net rate of formation of product B immediately following the addition of reactant A is __________.
positive
impossible to determine without additional information
negative
zero
positive
According to Le Chatelier's principle, an increase in the concentration of reactants will cause the reaction to shift to the right in order to re-establish equilibrium. Thus, immediately after reactant A is added, the forward reaction will increase and the net rate of formation of the products will be positive.
Example Question #5 : Principles Of Reaction Kinetics
Rate data is collected for a reaction, and the following integrated rate law is derived.
If this reaction is __________ with respect to reactant A, a plot of ln[A] versus time would be __________.
first order . . . linear
second order . . . parabolic
zero order . . . linear
first order . . . parabolic
first order . . . linear
The integrated rate law shown is for a reaction rate law with a first-order dependence on reactact A. If such a rate law accurately describes the kinetics of the reaction, then ln[A] will vary linearly with respect to time.
Example Question #6 : Principles Of Reaction Kinetics
Which of the following affects the rate of a reaction?
Frequency of collision
Molecules' energies
Collision orientation
All of these
All of these
Since reactant molecules collide and interact to break old bond and form new ones, any factors affecting collision and interactions will affect the reaction rate. Thus, increasing temperature will increase both the frequency of collisions and the average kinetic energy of the molecules. Enzymes bring molecules close to each other and orient them in a way that facilitates reactions.
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