Chapter 5.1

Question 1

What are reaction intermediates?

Answer 1

• they are molecules that are immediately consumed after they form
• > therefore, they are hard to detect

Question 2

What is the rate-determining step in a reaction

Answer 2

-it is the slowest step in a reaction mechanism

Question 3

What does the collision theory of chemical kinetics state

Answer 3

• states that the rate of a reaction is proportional to the number of collisions per second between reacting molecules
• > but not all collisions result in a chemical reaction

Question 4

What is an effective collision in terms of the collision theory of chemical kinetics

Answer 4

• an effective collision is one that:
• > has molecules colliding with each other in the correct orientation
• > also with sufficient energy to break their existing bonds and form new ones

Question 5

What is the activation energy

Answer 5

• it is the minimum energy of a collision necessary for a reaction to take place
• > only a fraction of colliding particles have enough kinetic energy to exceed that of the activation energy

Question 6

How does frequency factor in the Arrhenius equation change?

Answer 6

• it can increase by increasing the number of molecules in a vessel
• > when there are more molecules, there are more opportunities for collisions

Question 7

What is the energy magnitude of the transition state in comparison to the reactant and products

Answer 7

• it has greater energy than both the reactants and products

- >the reaction is at a point of maximum energy when it exists at the transition state

Question 8

Can the medium at which a reaction takes place affect its rate?

Answer 8

• yes
• > for example, some molecules are more likely to react with each other in an aqueous environment
• generally, polar solvents are preferred
• > because their molecular dipole polarizes the bonds of the reactants
• > thereby, lengthening and weakening them
• > permitting the reaction to occur faster

Question 9

How do catalysts increase the rate of a reaction?

Answer 9

• they may increase the frequency of collisions
• change the relative orientation of reactants
• donate electron density to the reactants
• reduce intramolecular bonding within the reactant molecules

Question 10

What is the difference between homogeneous catalysts and heterogeneous catalysts

Answer 10

Homogeneous
->catalyst is in the same phase(solid, gas, or liquid) as the reactants

Heterogeneous
->catalyst is in a different phase than the reactants