Gen Chem 2 Exam 2

kinetics

the area of chemistry that studies the rate at which a chemical process occurs

radioactive isotopes

chemical kinetics is important in the decay of ___ __ used in medicine

mechanism, occurs

the study of the individual “steps” of a reaction = reaction __ or how a reaction __

mechanisms

understanding reactions __allows scientists to maximize the efficiency and cost

physical, concentration, temperature, catalyst

factors that affect reaction rates

1. __ state of reactants

2. reactant __

3. reaction ___

4. presence of ___

homogeneous reactants

reactants that are all liquid or gas

rapidly

the more the reactant molecules collide, the more __ react

homogeneous

do homogeneous or heterogeneous reactants react more rapidly

heterogeneous reactants

reactants that are mixed phases of matter

heterogeneous reactants

reaction is limited by the area of contact of the reactants

larger

reactions with solids proceed more rapidly if the surface area is __

heterogeneous reactants

reactions with solids proceed more rapidly if the surface area is larger

more, increased

greater concentration of reactants results in __ frequent collisions, and __ reaction rates

few

low concentration = __ collisions

more

high concentration = __ collisions

kinetic

increasing temperature increases the __ energy of molecules

increases

greater kinetic energy __ the frequency of collisions and reaction rates

catalyst

agent that increase reaction rates without being used up in the reaction

collisions, mechanism

catalysts affect __ and the __ in a reaction

homogeneous

same phase of matter

heterogeneous

different phases of matter

rate

how fast a reaction occurs

slow

chemical reactions that have __ rates, have a smaller number of molecules react to form products over a specific amount fo time

fast

chemical reactions that have __ rates have many molecules react to form products over a specific amount of time

change in concentration of reactant/change in time

average rate =

true

true or false: reaction rate is positive

reactants

do reactants of products get a negative sign for average reaction rate

concentrations

the rate of reaction is not constant but changes with time because __ change with time

balanced

the rate of reaction is dependent on the ___ in a balanced equation

instantaneous rate

a rate at a particular time

concentration

the rate of a reaction often depends on the __ of one or more reactants

rate law

the relationship between the rate of the reaction and the concentration of he reactant

k[A]^n

rate =

concentration

the value of n determines how the rate depends on the __ of the reactant

zero order

rate is independent of the concentration of A

first order

rate is directly proportional to the concentration of A

second order

rate is directly proportional to the square of the concentration of A

constant, no, concentration

zero order with decomposition of N2O occurs on a hot platinum surface. reaction once surface is covered, rate is __.

when pt surface is completed covered with N2O molecules, an increase in N2O concentration has __ effect on the rate, since the molecule on the surface can react

the rate is constant because it is controlled by what happens on the pt surface, rather than the _
_ of N2O

sum

the overall order is the __ of m + n

experiment

the order of a reaction can only be determined by __

integrated rate law

expresses the concentration of a reactant as a function of time

order

the integrated rate law depends on the __ of the reaction

first order integrated rate law: rate

first

for a ___ order reaction, a plot of the natural log of reactant concentration as a function of time yields a straight line

second

for a ___ order reaction, a plot of the inverse of reactant concentration as a function of time yields a straight line

zero

for a ___ order reaction, a plot of the reactant concentration as a function of time yields a straight line

half life

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

t1/2

half life designated as

independent

for a first order reaction, t1/2 is __ of the initial concentration

1/k[A]0

Second Order Reaction: t1/2=

initial, not, twice

for a second order reaction, t1/2 depends on the __ concentration and is __ constant

each half-life is __ as long as the preceding one

0.693/k

First Order Reaction: t1/2 =

[A]0/2k

Zero Order Reaction: t1/2 =

initial, directly proportional, shorter

for a zero order reaction, t1/2 also depends on the __ concentration but is __ __ to the initial concentration

the half life gets __ as the concentration decreases

increases

as temperature __ so does reaction rate

increases, increases

as the average kinetic energy increases, the average molecular speed __ and thus collision rate __

activation energy

minimum energy needed for reaction

increases

as the temperature increases, the fraction of collisions with sufficient energy to react __

transition state or activated complex

the configuration of atoms at the maximum in the potential energy profile

kinetic, potential, transition, kinetic, products

as the reaction progresses, __ energy of the reactants is first converted to __ energy of the __ state and is then transformed into __ energy of the __

frequency factor

number of times the reactants approach the activation barrier per unit time with the correct orientation (A)

k

an increase in temperature generally results in an increase in __ = faster reaction rate

orientation, energy

molecules must collide with the correct __ and with enough __ to cause bond breakage and formation

do not

most chemical reactions _ __ occur in a single step, but through several steps

cannot

elementary steps __ be broken down into simpler steps - they occur as they are written

add

one of the requirements for a valid reaction mechanism is that the individual steps in the mechanism must __ to the overall reaction

reaction intermediate

formed in one step and consumed in another

reaction mechanism

a complete, detailed description of the reaction at the molecular level

molecularity

elementary steps are characterized by their __ = the number of reactant particles involved in the step

cannot, can

although the rate law for an overall chemical reaction __ be deduced from the balanced equation, the rate law for the elementary step __ be

three, three

elementary steps in which __ reactant particles collide are rare, because the probability of _ particles simultaneously colliding is small

slower

multi-step reactions have one-step that is much __ than all the others

slowest

reactants can become products only as fast as they can get through the __ step

rate-determining step

slowest step

true

true or false: the rate-determinging step determines the rate law for the overall reaction

sum, consistent

two conditions must be met for a proposed mechanism to be valid:

1. the elementary steps in the mechanism must __ to the overall reaction

2. the rate law predicted by the mechanisms must be __ with experimentally observed rate law

catalyst

increases the rate of a reaction by decreasing the activation energy of the reaction; change the mechanism by which the process occurs

homogeneous catalyst

a catalyst that is present in the same phase as reactants

heterogeneous catalyst

catalyst that exists in a different phase as the reactants

holding, break

one way a catalyst can speed up the reaction is by __ the reactants together and helping bonds __ bonds

enzymes

catalysts in biological systems

substrate, enzyme

the __ fits in the active site of the __ much like a key fits into a lock

chemical equilibrium

when a reaction and its reverse reaction proceed at the same rate

constant

once equilibrium is achieved, the amount of reactant and product remains __

either

equilibrium can be reached from __ direction

constant, temperature

the ratio of the rate of constants is __ at that __

law of mass action

defines an expression for a system at equilibrium in the gas phase

unitless

equilibrium constant is __

concentration, partial pressures

Keq is calculated as the ratio of __ or __ __ of products to reactants, causing the units to cancel out

no, not

pure solids and liquids have __ effect on equilibrium and are __ inluded in an equilibrium expression

constant

the concentrations of solids and liquids are __

expand

the concentration of pure solids and liquids does not change because they do not __ to fill its container

small; 10^-5 or smaller

K value that favors reactants

favors reactants

10^-5 or smaller

10^1

K value that favors neither

large; 10³ or larger

K value that favors products

favors neither

10^1

favors products

10³ or larger

reverse

the smaller the value of K, the more the __ rxn is favored

smaller

the __ the value of K, the more the reverse rxn is favored