Chapter 13

Question 1

Rate of Reaction

Answer 1

A measure of how fast the reaction occurs.

Rate = -(1/a)∙[ ∆[A] / ∆t ]

Question 2

Instantaneous Rate of Reaction

Answer 2

The rate at any one point in time

Question 3

Rate Law

Answer 3

Relationship between the rate of a reaction and the concentration of the reactants.

Rate = k[A]ⁿ

Rate = k[A]^m[B]ⁿ

Question 4

Overall order of Reaction

Answer 4

Sum of the exponents

Question 5

Half Life

Answer 5

The time required for the concentration of a reactant to fall to one-half of its initial value.

• First-Order Reaction: half-life is independent of initial concentration.
• Zero-Order and Second-Order half-lives depend on the initial concentration.

Question 6

Arrhenius Equation

Answer 6

k = Ae^-Ea/RT

• Relates the rate constant of a reaction to the temperature, activation energy, and frequency factor.

Question 7

Reaction Mechanism

Answer 7

• Series of individual chemical steps by which an overall chemical reaction occurs.
• Each step is an elementary step - cannot be broken down into simpler steps

Question 8

Molecularity

Answer 8

The number of reactant particles involved in an elementary step.

• A -> products : Unimolecular
• A+A -> products : Bimolecular
• A+B -> products : Bimolecular

Question 9

Termolecular Steps

Answer 9

Elementary steps in which three reactant particles collide.

Question 10

Rate-Determining Step

Answer 10

• Limits the overall rate of the reaction thus determining the rate law for the overall reaction.
• Slower than other elementary steps.

Question 11

Homogeneous Catalysis

Answer 11

Catalysis in which the catalyst exists in the same phase (or state) as the reactants.

Question 12

Heterogeneous Catalysis

Answer 12

Catalysis in which the catalyst and the reactants exist in different phases.

Question 13

Frequency Factor (A)

Answer 13

The number of times that the reactants approach the activation barrier per unit time.

Question 14

Exponential Factor (e)

Answer 14

• The fraction of approaches that are successful in surmounting the activation barrier and forming products.
• Increases with increasing temperature but decreases with increasing activation energy.

Question 15

Activation Energy

Answer 15

Energy barrier in a chemical reaction that must be overcome for the reactants to be converted into products.

Question 16

Arrhenius Equation - Linear Form

Answer 16

ln(k) = ln(A) - (Ea/R) x (1/T)

Question 17

Arrhenius Equation - Two Point Form

Answer 17

ln (k2/k1) = (Ea/R) x [(1/T1) - (1/T2)]

Question 18

Integrated Rate Law - Zero Order

Answer 18

• [A]_t = [A]_o- k_t
• Units of K: M∙s^-1

Question 19

Integrated Rate Law - First Order

Answer 19

• ln[A]_t = ln[A]_o- k_t
• Units of k: s^_-1

Question 20

Integrated Rate Law - Second Order

Answer 20

• 1/[A]_t = k_t + 1/[A]_o
• Units of k: M^-1∙s^-1

Question 21

Half-Life, Zero Order

Answer 21

t_1/2 = [A]_o/2k

Question 22

Half-Life, First Order

Answer 22

t_1/2 = 0.693/k

Question 23

Half-Life, Second Order

Answer 23

t_1/2 = 1/k[A]_o

Question 24

Rate Law - Zero Order Reaction

Answer 24

• n=0
• rate is independent of the concentration of A.

Question 25

Rate Law - First Order Reaction

Answer 25

• n=1
• rate is directly proportional to the concentration of A

Question 26

Rate Law- Second Order Reaction

Answer 26

• n=2
• rate is proportional to the square of the concentration of A.