Ch 2 exam

Question 1

the half life of a ____ order reaction is constant.

Answer 1

first

t1/2 = ln 2/k

Question 2

the half life of a reaction depends on the ____

Answer 2

order of the reaction

Question 3

rate of a first order reaction

Answer 3

rate = k [A]

Question 4

rate of a zero order reaction

Answer 4

rate = k

i.e. rate = k[A]^0 = k

Question 5

the half life of a zero order reaction DOES DEPEND on ____

Answer 5

the initial concentration of the reactant

t1/2= [A]0/2k

Question 6

the half life of a second order reaction DOES DEPEND on ____

Answer 6

the initial concentration of the reactant

t1/2 = 1/k*[A]0

Question 7

collision theory

Answer 7

reactants must collide in order to react with each other

1) rate of reaction is proportional to the rate of reactant collisions
2) molecules must be oriented properly when they collide
3) molecules must have adequate kinetic energy to react (activation energy)

Question 8

Ea

Answer 8

activation energy

minimum energy necessary to form a product during a collision between reactants

Question 9

catalyst

Answer 9

a substance that increases the rate of a chemical reaction by lowering the activation energy without itself being consumed

catalyst is regenerated in the process

provide an alternate reaction pathway with a lower activation energy

Question 10

homogeneous catalyst

Answer 10

in the SAME PHASE as the reactants. it speeds up the reaction by forming a reactive intermediate.

the reactive intermediate reacts further to form a product and regenerate the catalyst. the reactive intermediate is formed but immediately consumed.

Question 11

heterogeneous catalyst

Answer 11

in a different phase from that of the reactants.

usually the catalyst is a solid and the reactants are gas or liquid

Question 12

enzyme

Answer 12

biological HETEROGENEOUS catalyst

Question 13

reaction mechanism

Answer 13

the series of reactions that occurs to produce the overall observed reaction

most reactions occur in a series of small reactions involving one, two, or (at most) three molecules.

knowing the rate law of the reaction helps us determine the sequence of reactions in the mechanism

Question 14

intermediates

Answer 14

materials that are products in an early mechanism step, but then reactants in a later step

Question 15

molecularity

Answer 15

the number of reactant particles in an elementary step

unimolecular = one particle
bimolecular = two particles (can be the same type of particle)
termolecular = three particles

Question 16

rate law for an overall reaction must be determined ____

Answer 16

experimentally

Question 17

rate determining step

Answer 17

slowest step

the rate law of the rate determining step determines the rate law of the overall reaction

Question 18

chemical equilibrium

Answer 18

rates of both reaction and reverse reaction are equal

no further changes in concentration of either gas occurs unless the temperature or the volume of the container is changed

does NOT mean the amount of reactants and products are equal (just rates)

this is DYNAMIC equilibriumr

Question 19

reaction quotient, Q

Answer 19

mathematically expression of the the amounts of reactants and products present at any given point in a reversible reaction

can vary prior to equilibrium

can be calculated at any point in the reaction

often calculated at the start of the reaction using initial concentrations

Question 20

Qc vs Qp

Answer 20

Qc = amounts expressed in concentration; Molarity

Qc = [C]^c[D]^d / [A]^a[B]^b

Qp = partial pressures

Qp = P(C)^cP(D)^d / P(A)^aP(B)^b

Question 21

equilibrium constant, K

Answer 21

the value of Q when the reaction is at equilibrium

Kc = Qc at equilibrium

K is unitless

Question 22

law of mass action

Answer 22

states that the values of the equilibrium constant expressions are a constant for a particular reaction, at a given temperature

the relationship between the chemical equation and concentrations of reactants and products

Question 23

The value of the equilibrium constant K is independent of:

Answer 23

the starting amounts of reactants and products

Question 24

The value of the equilibrium constant K is dependent on:

Answer 24

the temperature of the system

Question 25

the magnitude of an equilibrium constant indicates:

Answer 25

the extent of a reaction

Question 26

K and Q are

Answer 26

unitless

Question 27

If K is very small:

Answer 27

the mixture contains mostly reactants at equilibrium

Question 28

If K is very large:

Answer 28

the mixture contains mostly products at equilibrium

Question 29

The value of K gives no indication as to:

Answer 29

whether the reaction is fast or slow

Question 30

K (backward) =

Answer 30

1/K (forward)

Question 31

Q<K

Answer 31

reaction forms products;
shift R

Question 32

Q>K

Answer 32

reaction forms reactants;
shift L

Question 33

Q=K

Answer 33

equilibrium

Question 34

homogenous equilibrium

Answer 34

all the reactants and products are present in the same phase

Question 35

all ___ and ___ phase species appear in the Kc expression

Answer 35

aqueous and gas

Question 36

K = 1

Answer 36

doesn’t favor reactants or products

Question 37

K &laquo_space;1 (much smaller than 1)

Answer 37

reverse rxn is favored

Question 38

Q»1 (much larger)

Answer 38

reaction has more products than reactants

Question 39

the relationship between Kp and Kc

Answer 39

Kp = Kc (RT) ^n

Question 40

heterogeneous equilibrium

Answer 40

reaction mixture that contains reactants and products that are in two or more different phases

Pure solids and pure liquids DO NOT appear in the K expression

equilibrium is independent of the amount of solid or liquid present as long as at least some is present in the reaction mixture

Question 41

le Chatelier’s principle

Answer 41

when a chemical system at equilibrium is disturbed, it returns to equilibrium by counteracting the disturbance

disturbance causes a change in Q. reaction will shift to re-establish Q= K

Question 42

ways equilibrium can be disturbed

Answer 42

1. adding or removing a reactant or product
2. changing the pressure
3. changing the temperature

Question 43

adding or removing a pure liquid or solid:

Answer 43

has no effect on the system unless all the liquid or solid is removed

Question 44

pressure changes will effect the equilibrium if:

Answer 44

the reaction contains gas phase species AND n is NOT equal to 0

Question 45

exothermic reaction will shift

Answer 45

left

Question 46

endothermic reaction will shift

Answer 46

right