Ch. 5: Chemical Kinetics

Question 1

Change in Gibbs Free Energy (🔺G)

Answer 1

Determines whether or not a reaction is spontaneous

Question 2

Chemical Mechanisms

Answer 2

Propose a series of steps that make up the overall reaction

Question 3

Intermediates

Answer 3

Molecules that exist within the course of a reaction that are neither reactants nor products overall

Question 4

Rate-determining step

Answer 4

Limits the maximum rate at which the reaction can proceed

Question 5

Collision Theory

Answer 5

States that a reaction rate is proportional to the number of effective collisions between the reacting molecules

Question 6

Activation Energy

Answer 6

For a collision to be effective, molecules must be in the proper orientation and have sufficient kinetic energy to exceed the activation energy

Question 7

Arrhenius Equation

Answer 7

Mathematical way of representing collision theory: Ae^(-Ea/RT)

Question 8

Transition State Theory

Answer 8

States that molecules form a transition state or activated complex during a reaction in which the old bonds are partially dissociated and the new bonds are partially formed

• From this state, the rxn can proceed toward products or revert back to reactants
• The transition state is the highest point on a free energy reaction diagram

Question 9

Factors that affect reaction rate

Answer 9

• increasing the concentration of reactant will increase reaction rate (except fro zero-order reactions) because there are more effective collisions per time
• increasing the temp will increase rxn rate bc the particles’ kinetic energy is increased
• changing the medium can increase or decrease reaction rate depending on how the reactants interact w the medium
• adding a catalyst increases reaction rate because it lowers the activation energy

Question 10

Homogeneous Catalysts

Answer 10

Same phase as the reactants

Question 11

Heterogeneous Catalysts

Answer 11

Different phase as reactants

Question 12

Measurement of Reaction Rates

Answer 12

Measured in terms of the rate of disappearance of a reactant or appearance of a product

Question 13

Rate Laws

Answer 13

Take the form of rate = k[A]^x[B]^y; must be determined from experimental data

Question 14

Rate Orders

Answer 14

Usually do not match the stoichiometric coefficients; sum of all individual rate orders in the rate law

Question 15

Zero-order reactions

Answer 15

Have a constant rate that does not depend on the concentration of a reactant

• Rate can only be affected by changing the temperature or adding a catalyst
• Concentration vs Time curve of a zero order rxn is a straight line; the sope of such a line is equal to -k

Question 16

First order reactions

Answer 16

Have a nonconstant rate that depends on the concentration of reactant
- Concentration vs Time curve of a zero order rxn is nonlinear; the slope of ln[A] vs time is equal to -k

Question 17

Second Order Reaction

Answer 17

Have a nonconstant rate that depends on the concentration of reactant
- Concentration vs Time curve of a zero order rxn is nonlinear; the slope of 1/[A] vs time is equal to k

Question 18

Broken Order Reactions

Answer 18

Those w noninteger orders

Question 19

Mixed order reactions

Answer 19

Those that have rate order that changes over time