Chem 2 Exam 2 (LO 23-42)

Regarding the Arrhenius equation, reaction rate decreases as

Ea increases

______ _____ cannot be broken down into simpler steps.

elementary steps

What is activation energy?

energy barrier that must be surmounted for the reactants to be transformed into products

In the Arrhenius Equation, what are the units for Ea and T?

J/mol Kelvin

What is the equation that relates Kc and Kp?

Kp = Kc (RT)^n

The rate at which the reaction occurs depends on: A-A+B -> A-B+A

1 - Concentration of reacting particles 2 - Temperature 3 - Structure and relative orientation of the reacting particles

What does the Arrhenius Equation Two Point Form compare?

compares rate constant at two different temperatures

What is the integrated rate law for second order? What is the slope?

1/[A]t = kt + 1/[A]0 k

What does rate law (differential rate law) show? EX?

how rate depends on concentration Rate = k[A]m[B]n

Which of the following is/are true?How can you make the incorrect statements true? A - For the reaction A → B + 2C where the reaction is determined to be first order, if the initial rate is 0.04 M/s when [A] = 0.20 M, then the initial rate will be 0.02 M/s when [A] = 0.10 M. B - For the reaction A → 2 B where the reaction is determined to be second order, if the initial rate is 0.08 M/s when [A] = 0.10 M, then the initial rate will be 0.32 M/s when [A] = 0.20 M. C - For the reaction A → B where the reaction is determined to be zero order, if the initial rate is 0.5 M/s when [A] = 1.2 M, then the initial rate will be 0.5 M/s when [A] = 0.60 M. D - For the reaction A + B + 2 C → 3 D + E, if the rate law is Rate = k [A][C]2, then the overall order of the reaction is 3.

A, B, C, & D

Which of the following is/are true? How can you make the incorrect statements true? A - The differential rate law shows how the concentration depends on time; the integrated rate law shows how rate depends on concentration B - In the differential rate law, k is the same rate constant as in the integrated rate law C - The integrated rate law must be determined experimentally; the rate law (differential rate law) is derived from the integrated rate law mathematically D - When the inverse of the concentration of reactant X is plotted vs time, a straight line will result if the reaction is second-order in X E - When the natural log of the concentration of a reactant X is plotted vs time, a straight line will result if the reaction is zero-order in X

B & D A - The integrated rate law shows how the concentration depends on time; the differential rate law shows how rate depends on concentration C - The rate law (differential) must be determined experimentally; the integrated rate law is derived from the integrated rate law mathematically E - When the natural log of the concentration of a reactant X is plotted vs time, a straight line will result if the reaction is first-order in X

What is the integrated rate law for first order? What is the slope?

ln[A]t = -kt + ln[A]0 -k

Which of the following is/are true? How can you make the incorrect statements true? A - According to collision theory, rate of reaction decreases with increasing temperature because more particles have enough energy to overcome the activation energy B - According to collision theory, rate of reaction decreases with increasing concentration because particles are less likely to collide with one another C - For the reaction 2 A + B + C → 3 D + E, if the rate at an instant in time is -0.28 M/s for A, then the rate for D is +0.42 M/s. D - Rate of reaction generally decreases with time.

C & D A - According to collision theory, rate of reaction increases with increasing temperature because more particles have enough energy to overcome the activation energy B - According to collision theory, rate of reaction increases with increasing concentration because particles are more likely to collide with one another.

Regarding the Arrhenius equation, reaction rate increases as

T increases

What is the integrated rate law of zero order? What is the slope?

[A]t = -kt + [A]0 -k

What is an intermediate?

an intermediate is a complex that appears during the course of a reaction but does not appear in the net reaction, or as a final product

For a first order reaction, the half-life is...

constant and independent of concentration

The reactant concentration _________ with time, and so does the _____ _____.

decreases average rate

Rate law can also be called what?

differential rate law

In second order reactions, each consecutive half life is ___ in time

doubled

______ _____ for a chemical reaction is the condition in which the rate of the forward reaction equals the ate of the reverse reaction

dynamic equillibrium

Order of a reaction can only be determined by _____ it is not determined by the _____ in the balanced chemical equations.

experiment coefficients

The half-life (t1/2) of a reaction is the time required for the concentration of a reactant to

fall to one-half of its initial volume

A-A+B -> A-B+A A-X+B -> A-B+X We would expect the _____ reaction to have a higher rate of reaction.

first B can collide with A-A from any direction B must collide with A-X to form a bond with A

The reaction rate is _____ when it just begins. It is always ______.

greatest positive

In second order reactions, each consecutive half life is ___ in time

halved

In ________ catalysis, the catalyst exits in a different phase/state as the reactants

heterogenous

In ________ catalysis, the catalyst exits in the same phase/state as the reactants

homogenous

For rate vs reactant concentration Zero order = _____ line First order = _____ line Second order = _____ line

horizontal, flat straight, positive slope curved, positive slope

What does integrated rate law show? EX?

how concentration depends on time (mathematically) ln[A]t = -kt + ln[A]0

A catalyst is a substance that ______ the rate of a chemical reaction but is not _______ in the reaction

increases consumed

According to collisions theory, an increase in concentration of the reacting particles ________ reaction rate

increases (positive correlation)

As temperature increases, rate of reaction

increases (positive correlation)

As temperature _________, the fraction of molecules with enough energy to surmount the activation energy barrier also _________

increases 2x

What is the Arrhenius equestion?

k = Ae^(-Ea/RT)

For the reaction aA+bB -> cC+dD Rate = The overall order is the sum of the _____

k(A)^m (B)^n exponents (m+n)

If Q>K, the reaction shifts ____ to produce more _____ to achieve equilibrium

left reactant

What is the Arrhenius Equation Two Point Form?

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

Elementary steps are characterized by what? What is this?

molecularity number of reactant particles involved in the step

The concentrations of reactants and products are ________ at equilibrium

not necessarily equal

What are the 2 conditions that must be met for a proposed reaction mechanism to be considered valid?

the elementary steps in the mechanism must sum to the overall reaction the rate law predicted by the mechanism must be consistent with the experimentally observed rate law

k is always...

positive

Rate=k(A)^n where k = n =

rate constant reaction order

The Arrhenius equation shows the relationship between the ____ ________ (_), and the __________ (_)

rate constant (k) temperature (K)

The _______ elementary step in a reaction mechanism determined the overall rate of the reaction and is called the _________ or _______ step.

rate limiting OR rate determining

A _____ _____ shows the series of individual chemical steps by which an overall chemical reaction occurs using a series of elementary steps.

reaction mechanism

If Q<K, the reaction shifts ____ to produce more _____ to achieve equilibrium

right product

What determines the rate law for the overall reaction?

slowest elementary step

The equilibrium constant (K) indicates the ratio at equilibrium of products and reactants raised to their _____ _____

stoichiometric coefficients

What is the formula of half life for first order reactions?

t1/2 = .693/k

What is the formula of half life for second order reactions?

t1/2 = 1/(k[A]0)

What is the formula of half life for zero order reactions?

t1/2 = [A]0 / 2k

For reactant concentration vs time Zero order = _____ line First order = _____ line Second order = _____ line

top line, negative slope, curved middle line, negative slope, curved bottom line, negative slope, straight

If n (reaction order) = 0 = 1 = 2

zero order and rate is constant first order and rate is directly proportional to concentration second order and rate is dependent on concentration to the second order