Chapter 14 & 15

Question 0

activation energy (Ea)

Answer 0

The minimum energy needed for reaction; the height of the energy barrier to formation of products. (Section 14.5)

Question 1

activated complex (transition state)

Answer 1

The particular arrangement of atoms found at the top of the potential-energy barrier as a reaction proceeds from reactants to products. (Section 14.5)

Question 2

active site

Answer 2

Specific site on a heterogeneous catalyst or an enzyme where catalysis occurs. (Section 14.7)

Question 3

adsorption

Answer 3

The binding of molecules to a surface. (Section 14.7)

Question 4

Arrhenius equation

Answer 4

An equation that relates the rate constant for a reaction to the frequency factor, A, the activation energy, Ea, and the temperature, T:K.

Question 5

Beer’s law

Answer 5

The light absorbed by a substance (A) equals the product of its extinction coefficient (e), the path length through which the light passes (b), and the molar concentration of the substance (c): A

Question 6

bimolecular reaction

Answer 6

An elementary reaction that involves two molecules. (Section 14.6)

Question 7

catalyst

Answer 7

A substance that changes the speed of a chemical reaction without itself undergoing a permanent chemical change in the process. (Section 14.7)

Question 8

chemical equilibrium

Answer 8

At equilibrium the concentrations of the reactants and products remain constant. (Chapter 15: Introduction)

Question 9

chemical kinetics

Answer 9

The area of chemistry concerned with the speeds, or rates, at which chemical reactions occur. (Chapter 14: Introduction)

Question 10

collision model

Answer 10

A model of reaction rates based on the idea that molecules must collide to react; it explains the factors influencing reaction rates in terms of the frequency of collisions, the number of collisions with energies exceeding the activation energy, and the probability that the collisions occur with suitable orientations. (Section 14.5)

Question 11

elementary reaction

Answer 11

A process in a chemical reaction that occurs in a single event or step. An overall chemical reaction consists of one or more elementary reactions or steps. (Section 14.6)

Question 12

enzyme

Answer 12

A protein molecule that acts to catalyze specific biochemical reactions. (Section 14.7)

Question 13

equilibrium constant

Answer 13

The numerical value of the equilibrium-constant expression for a system at equilibrium. The equilibrium constant is most usually denoted by Kp for gas-phase systems or Kc for solution-phase systems. (Section 15.2)

Question 14

equilibrium-constant expression

Answer 14

The expression that describes the relationship among the concentrations (or partial pressures) of the substances present in a system at equilibrium. The numerator is obtained by multiplying the concentrations of the substances on the product side of the equation, each raised to a power equal to its coefficient in the chemical equation. The denominator similarly contains the concentrations of the substances on the reactant side of the equation. (Section 15.2)

Question 15

first-order reaction

Answer 15

A reaction in which the reaction rate is proportional to the concentration of a single reactant, raised to the first power. (Section 14.4)

Question 16

frequency factor (A)

Answer 16

A term in the Arrhenius equation that is related to the frequency of collision and the probability that the collisions are favorably oriented for reaction. (Section 14.5)

Question 17

Haber process

Answer 17

The catalyst system and conditions of temperature and pressure developed by Fritz Haber and coworkers for the formation of NH3 from H2 and N2. (Section 15.2)

Question 18

half-life

Answer 18

The time required for the concentration of a reactant substance to decrease to half its initial value. (Section14.4)

Question 19

heterogeneous catalyst

Answer 19

A catalyst that is in a different phase from that of the reactant substances. (Section 14.7)

Question 20

heterogeneous equilibrium

Answer 20

The equilibrium established between substances in two or more different phases, for example, between a gas and a solid or between a solid and a liquid. (Section 15.4)

Question 21

homogeneous catalyst

Answer 21

A catalyst that is in the same phase as the reactant substances. (Section 14.7)

Question 22

homogeneous equilibrium

Answer 22

The equilibrium established between reactant and product substances that are all in the same phase. (Section 15.4)

Question 23

instantaneous rate

Answer 23

The reaction rate at a particular time as opposed to the average rate over an interval of time. (Section 14.2)

Question 24

intermediate

Answer 24

A substance formed in one elementary step of a multistep mechanism and consumed in another; it is neither a reactant nor an ultimate product of the overall reaction. (Section 14.6)

Question 25

law of mass action

Answer 25

The rules by which the equilibrium constant is expressed in terms of the concentrations of reactants and products, in accordance with the balanced chemical equation for the reaction. (Section 15.2)

Question 26

Le Châtelier’s principle

Answer 26

A principle stating that when we disturb a system at chemical equilibrium, the relative concentrations of reactants and products shift so as to partially undo the effects of the disturbance. (Section 15.7)

Question 27

lock-and-key model

Answer 27

A model of enzyme action in which the substrate molecule is pictured as fitting rather specifically into the active site on the enzyme. It is assumed that in being bound to the active site, the substrate is somehow activated for reaction. (Section 14.7)

Question 28

molecularity

Answer 28

The number of molecules that participate as reactants in an elementary reaction. (Section 14.6)

Question 29

overall reaction order

Answer 29

The sum of the reaction orders of all the reactants appearing in the rate expression when the rate can be expressed as rate

Question 30

rate constant

Answer 30

A constant of proportionality between the reaction rate and the concentrations of reactants that appear in the rate law. (Section 14.3)

Question 31

rate law

Answer 31

An equation that relates the reaction rate to the concentrations of reactants (and sometimes of products also). (Section 14.3)

Question 32

rate-determining step

Answer 32

The slowest elementary step in a reaction mechanism. (Section 14.6)

Question 33

reaction mechanism

Answer 33

A detailed picture, or model, of how the reaction occurs; that is, the order in which bonds are broken and formed and the changes in relative positions of the atoms as the reaction proceeds. (Section 14.6)

Question 34

reaction order

Answer 34

The power to which the concentration of a reactant is raised in a rate law. (Section 14.3)

Question 35

reaction quotient (Q)

Answer 35

The value that is obtained when concentrations of reactants and products are inserted into the equilibrium expression. If the concentrations are equilibrium concentrations, Q

Question 36

reaction rate

Answer 36

A measure of the decrease in concentration of a reactant or the increase in concentration of a product with time. (Section 14.2)

Question 37

second-order reaction

Answer 37

A reaction in which the overall reaction order (the sum of the concentration-term exponents) in the rate law is 2. (Section 14.4)

Question 38

substrate

Answer 38

A substance that undergoes a reaction at the active site in an enzyme. (Section 14.7)

Question 39

termolecular reaction

Answer 39

An elementary reaction that involves three molecules. Termolecular reactions are rare. (Section 14.6)

Question 40

transition state (activated complex)

Answer 40

The particular arrangement of reactant and product molecules at the point of maximum energy in the rate-determining step of a reaction. (Section 14.5)

Question 41

unimolecular reaction

Answer 41

An elementary reaction that involves a single molecule. (Section 14.6)

Question 42

What are factors that affect reaction rates?

Answer 42

1. Physical state of the reactants 2. Reactants concentrations 3. Temperature 4. Presence of a catalyst

Question 43

What does it mean if k is 0?

Answer 43

There is no reaction