Unit 4 - Chemical Kinetics

Question 1

The study of the rates of chemical reactions.

Answer 1

Chemical kinetics

Question 2

Change in concentration of a reactant or product per unit time.

Answer 2

Reaction rate

Question 3

Factors that affect reaction rate.

Answer 3

Concentration
Activation energy
Nature of reactants
Temperature

Presence of catalyst
Molecular collisions

Question 4

It explains why the other factors affect the rate of reaction.

Answer 4

Collision theory

Question 5

Which of the following states that for the reaction to occur atoms or molecules or ions in a reaction system must do?

A. Collide.
B. Collide with enough energy to break and form bonds.
C. Collide with the proper orientation for a reaction to occur.
D. All of the above.

Answer 5

D

Question 6

A collision that results in a reaction.

Answer 6

Effective collision

Question 7

T/F
Reaction rate is proportional to effective collisions.

Answer 7

T

Question 8

Also known as activated-complex theory.

Answer 8

Transition state theory

Question 9

Transition state theory postulates that reactants form a high energy intermediate, the _____, which then falls apart into the products.

Answer 9

Transition state

Question 10

T/F
For a reaction to occur, the reactants must acquire sufficient energy to form the transition state.

Answer 10

T

Question 11

This energy is called the _____.

Answer 11

Activation energy or Ea

Question 12

Minimum amount of energy required to initiate a chemical reaction.

Answer 12

Activation energy (Ea)

Question 13

T/F
For any reactant, the bond type, strength, and number determine the Ea required for a successful collision.

Answer 13

T

Question 14

Increased reaction rate is observed when reactants have _____ bonds.

Answer 14

Fewer and weaker

Question 15

Reactions between MOLECULES are usually _____ than reactions between IONS.

Answer 15

Slower

Question 16

T/F
Some reactions involve complicated molecular substances or complex ions are often more reactive than smaller, less complex entities.

Answer 16

F

Question 17

Increase in concentration of _____ increases the likelihood for reactant molecules to collide (increase the reaction rate).

Answer 17

Reactants

Question 18

Reducing volume or increasing pressure on a gas will cause a concentration to _____.

Answer 18

Increase

Question 19

Increasing the surface area of a solid _____ the concentration of available particles.

Answer 19

Increases

Question 20

T/F
The average rate decreases as the reaction proceeds. This is because as the reaction goes forward, there are fewer collisions between reactant molecules.

Answer 20

T

Question 21

T/F
The average rate of reaction over each interval is the change in concentration over change in time.

Answer 21

T

Question 22

A constant of proportionality between the reaction rate and the concentration of reactant.

Answer 22

Rate constant (k)

Question 23

T/F
Rate is directly proportional to the concentration of the reactant.

Answer 23

T

Question 24

T/F
Each reaction has its own equation that gives its rate as a function of reactant concentrations.

Answer 24

T

Question 25

Expresses how the rate depends on concentration.

Answer 25

Differential rate law (rate law)

Question 26

T/F Rate law is the expression that gives the rate as a function of concentration.

Answer 26

T

Question 27

T/F Rate law expresses the relationship of the rate of a reaction to the rate constant and the concentrations of the reactants raised in some powers.

Answer 27

T

Question 28

If aA → products, then the rate law is?

Answer 28

rate = k[A]^x

Question 29

T/F Reaction order (x) is determined experimentally.

Answer 29

T

Question 30

It specifies the relationship between concentration of reactant and the reaction rate.

Answer 30

Reaction order (x)

Question 31

T/F Reaction order is not related to stoichiometric coefficient of the reactant in the balanced equation.

Answer 31

T

Question 32

Reaction order is always defined in terms of _____.

Answer 32

Reactant concentrations

Question 33

What is the reaction order when [A] increase 2x and rate is NOT affected.

Answer 33

Zero order

Question 34

What is the reaction order when [A] increase 2x and rate increase 2x.

Answer 34

First order

Question 35

What is the reaction order when [A] increase 2x and rate increase 4x.

Answer 35

Second order

Question 36

If aA + bB→ products, then the rate law expression is?

Answer 36

rate = k[A]^x[B]^y

Question 37

It is defined as the sum of the exponents on the reactants in the rate law.

Answer 37

Overall order of reaction (x+y)

Question 38

Overall balanced chemical equation does not tell how a reaction actually takes place, but a _____ does.

Answer 38

Reaction mechanism

Question 39

Sequence of elementary steps that leads to product formation.

Answer 39

Reaction mechanism

Question 40

A sum of elementary steps or elementary reactions.

Answer 40

Reaction mechanism

Question 41

A series of simple reactions that represent the progress of the overall reaction.

Answer 41

Reaction mechanism

Question 42

It is one step in a series of simple reactions that show the progress of a reaction at the molecular level.

Answer 42

Elementary step

Question 43

Refers to the number of molecules reacting in an elementary step.

Answer 43

Molecularity of a reaction

Question 44

It appears in the reaction mechanism but not in the overall balance equation.

Answer 44

Intermediate

Question 45

The first elementary step is the _____.

Answer 45

Rate-determining step

Question 46

The slowest steps in sequence of steps leading to product formation.

Answer 46

Rate-determining step

Question 47

T/F The rate-determining step will give you the rate law expression.

Answer 47

T

Question 48

Which of the following is/are true when temperature increases? A.. Molecules move faster. B. High kinetic energy. C. More molecular collisions. D. Higher reaction rates. E. All of the above

Answer 48

E

Question 49

T/F At higher temperatures, the fraction of molecules with energy equal to or greater than the Ea also increases.

Answer 49

T

Question 50

A substance that increases the rate of a chemical reaction without itself being consumed.

Answer 50

Catalyst

Question 51

Catalyst may react to form an _____, but it is regenerated in the subsequent step of the reaction.

Answer 51

Intermediate

Question 52

Catalyst increases the rate by _____ of the reaction.

Answer 52

Lowering the activation energy

Question 53

Reactants and catalyst are in different phases.

Answer 53

Heterogenous catalyst

Question 54

Examples of heterogeneous catalyst.

Answer 54

Haber synthesis of ammonia Ostwald process of HNO3 Catalytic converters

Question 55

Reactants and catalyst are in dispered in a single phase.

Answer 55

Homogeneous catalyst

Question 56

Examples of homogeneous catalyst.

Answer 56

Lead chamber process – for the production of H2SO4 Acid-base catalysts

Question 57

It involves enzymes (biological catalysts) that have active site that specifically bind to substrates (reactants).

Answer 57

Enzyme catalysis