Gen. Chem 2: Chapter 17
which one of the following options is equal to reaction rate, given rate = (change [A]/change in temp.) for the reaction A (g) -> products?
change Pa/RT*change in temp.
a reaction energy diagram plots potential ___ versus reaction ___
- energy - progress
if ln[A] = y, [A] -
e^y
which of the following is the correct expression for the half-life of a first-order reaction?
t1/2 = 0.693/k
the dimizeration of butadiene proceeds according to second-order kinetics. if the rate constant at a particular temperature is 0.100M^-1 min^-1, calculate the half-life for an initial reactant concentration of 0.35 M
t1/2 = 29min; t1/2 = 1/k[A]o = 1/0.100*0.35 = 29 min
for the reaction A -> product, in which of the following situations should the equation ln[A]t = -kt + ln[A]o be used?
this equation should be used to calculate the concentrations of reactant A at a given time if the reaction is first order in A
match each mechanism shown to the correct description of species A - A + B2 -> AB2 AB2 -> 2B + A - AB2 -> A + B2 A + C -> AC - A + B2 -> AB + B B + C -> BC - AB2 -> A + B2 B2 -> 2B
- A is a catalyst; A is used in one step and then represented in a later step. A is not in the overall reaction - A is an intermediate; A is formed in one step and then used up in a later step. A is not in the overall reaction - A is a reactant; A is on the left side and appears in the overall reaction - A is a product; A is on the right side and appears in the overall reaction
for the reaction A -> B, determine the time period over which the average rate of decrease of A is the greatest, based on the data below time (s): 0.0; 30.0; 60.0; 90.0; 120.0 [A] (M): 1.00; 0.50; 0.250; 0.13; 0.06
between time 0s and time 30s; the average rate of change of [A] over the first 30 seconds is equal to (.50M - 1.00M)/(30s-0s) = -.017M/s. this is the greatest rate of change over a given time interval in the table
a reaction is first order with respect to reactant A. doubling initial concentration of A would have what effect on the initial reaction rate? A -> products
double the reaction rate
the individual steps that make up a reaction mechanism are called ___ reactions or steps
elementary
which of the following data tables represents the information needed to determine the rate law for the following reaction? A -> products
experiment: [A] (M): initial rate (M/s): 1 0.15 1.5*10^-2 2 0.30 3.0*10^-2
for the general reaction A -> products, a plot of ln[A] vs. time gives a straight line. what is the order of this reaction with respect to A?
first order
in the arrhenius equation k = Ae ^-Ea/RT if T increases the magnitude of the negative exponent become ___, which means k becomes ___, and the rate ___
- smaller, larger, increases
the concentration of oxygen is being monitored in a reaction flask. the amount of O2 present is found to be 45.0ppm after 15s and 40.0ppm after 25s. what is the average rate of change of oxygen (in ppm/s) during this time interval?
.50ppm/s
calculate the value of [A]t using the equation below, if k=2.0*10^-2s^-1, t=30.0s, and [A]o=0.50M ln[A]=-kt + ln[Ao]
0.28M
the ___-___ of a reaction is the time required for the reactant concentration to reach half its initial value
half-life
a reaction is second order with respect to reactant A. doubling the initial concentration of A would have what effect of the initial reaction rate? A -> products
increase the reaction rate by a factor of four
slight variations in the calculated values of k are due to experimental deviations. given the following data (shown), match the rate constant at each time to the calculated value of k for the first order: A -> products time (s): [A] (M): rate (M/s): 0.0 0.0150 1.50*10^-3 1.5 0.0128 1.38*10^-3 2.5 0.0115 1.21*10^-3 5.0 0.00896 9.23*10^-4
k at t-0.0s = 1.00*10^-1s^-1 k at t=1.5s = 1.08*10^-1s^-1 k at t=2.5s = 1.05*10^-1s^-1 k at t=5.0s = 1.03*10^-1s^-1 k = rate/[A]
the half-life equation for a first-order reaction (t = 0.693/k) is derived from what equation?
ln [A]/[A]o = -kt
chemical kinetics studies the ___ of chemical reactions, i.e., how fast reactants are converted into products
rate
the ___ constant, given the symbol k, expresses the relationship between reactant concentration and reaction rate for a given reaction
rate
what are the most common types of heterogeneous catalysts?
solids
the equation below is associated with what order with respect to reactant A? [A]t = -kt + [A]o
zero-order
identify the reaction intermediate (s) in the reaction mechanism shown 1. (CH3)3C-Br (aq) -> (CH3)3C^+ (aq) + Br^- (aq) [slow] 2. (CH3)3C^+ (aq) + H2O (l) -> (CH3)3C-OH2^+ (aq) [fast] 3. (CH3)3C-OH2^+ (g) -> H^+ (aq) + (CH3)3C-OH (aq) [fast]
- (CH3)3C-OH2^+ - (CH3)3C^+ a reaction intermediate is a species that is formed and used up during a reaction
match each chemical reaction to the number of ways the reaction rate can be written - A -> B - A + B -> 2C - 2A + B -> C + D - A + B + C -> D + E
- 2 ways - 3 ways - 4 ways - 5 ways
select all of the bimolecular elementary steps among the choices below
- 2A -> B + C - 2A -> B - A + B -> C + D
the steps below are proposed for a reaction mechanism: H2 + NO -> H2O + N N + NO -> N2 + O O + H2 -> H2O which of the following appear as reactants, shown with the correct coefficient in each case, in the overall balanced chemical equation?
- 2H2; the overall chemical equation is 2H2 + 2NO -> 2H2O + N2 - 2NO
match each rate law correctly to the associated rate-determining step. assume that each of the rate-determining steps listed below is the first step in the reaction mechanism and that they are all elementary steps - rate = k[A][B] - rate = k[A]^2 - rate = k[B] - rate = k[B]^2
- A + B -> C + D - 2A -> B + C - B -> C - 2B -> 2C
which elementary step in the proposed mechanism is the rate-determining step?
X (g) + C (g) -> Y (g); [slow] the slowest step is the rate determining step
what is the reaction intermediate in this two-step mechanism? 1. X + O3 -> XO + O2 2. XO + O -> X + O2
XO; a reaction intermediate is formed and used up during the course of a reaction
select all of the statements that correctly describe a second-order reaction. use the example: A -> products
- a second-order reaction involving a single reactant has a rate that depends on the concentration of that reactant raised to the second power - the rate law for a reaction that is second order in reactant A is: rate = k[A]^2 - if the initial concentration of A is doubled the reaction rate increased by a factor of four
match each rate law to the correct units for the rate constant k - rate = k - rate = k[A] - rate = k[A][B] - rate = k[A][B]^2
- M/s - 1/s - 1/Ms - 1/M^2s
which of the following elementary reactions are unimolecular?
- N2O4 (g) -> 2NO2 (g) - PCl5 (g) -> PCl3 (g) + Cl2 (g)
consider the reaction 2H2 (g) + O2 (g) -> 2H2O (g). at a particular moment in the reaction, H2 (g) is disappearing at a rate of 0.024 M/s. select all the statements that correctly describe this reaction
- O2 (g) is being used up at a rate of 0.012 M/s - H2O (g) is being formed at a rae of 0.024 M/s
in a given reaction, the rate may be expressed as either rate = -change in concentrations [Y]/change in temperature, or as rate = change in concentration [X]/change in temperature. what must be true about X or Y if the reaction is proceeding in the forward direction?
- Y is a reactant; its concentration decreases with time; the negative sign in the rate expression accounts for this - X is a product
the reaction 2NO (g) + 2H2 (g) -> N2 (g) + 2H2O (g) is found to obey the following rate law rate = k[NO][H2]^2, where k=5.0*10^2 M^2s^-1. rank the following sets of concentrations in order of reaction rates, with the highest rate conditions appearing at the top of the list first
- [NO] = 2.0*10^-2 M; [H2] = 1.0*10^-1M (rate = 0.10 M/s) - [NO] = 1.0*10^-2 M; [H2] = 1.0*10^-1 M (rate = 5.0*10^-2 M/s) - [NO] = 2.0*10^-2 M; [H2] = 5.0*10^-2 M/s (rate = 2.5*10^-2 M/s) - [NO] = 4.0*10^-2 M; [H2] = 1.0*10-2 M (rate = 2.0*10^-3 M/s)
which of the following options correctly describe heterogeneous catalysis?
- a catalytic converter in a car is used to speed up the oxidation of CO and unburned hydrocarbons to CO2 and H2O - a solid catalyst is used in the haber process to more rapidly produce ammonia - a catalyst in the same phase (gas) as the reactants is a homogeneous catalyst
the characteristics of a first-order reaction (A -> products) include ___
- a reaction rate that depends on the concentration of A raised to the first power - a rate law of the format: rate = k[A]
which of the following statements correctly describe the straight-line plot obtained from concentration and time data for the first-order reaction A -> products?
- a straight line is obtained by plotting ln[A] versus time - the slope of the line is negative; the slope of the line is equal to -k - the rate constant for the reaction is related to the slope of the straight line
select all the statements that correctly describe an elementary reaction
- an elementary reaction occurs in a single collision of the reacting particles - an elementary reaction is a single step in a reaction mechanism - an overall reaction is the sum of all the elementary reactions
match the changes in temperature and activation energy (Ea) for a given reaction with their effect on the rate and rate constant of a reaction - a decrease in Ea leads to - a decreased in temperature leads to - k increases - k decreases
- an increase in rate - a decrease in rate - if temperature increases - if Ea increases
which of the following conditions must be satisfied for a collision between reactants to be effective?
- appropriate molecular orientation - enough energy to overcome Ea - reaction rate is increased with high temperature but the effectiveness of an individual collision does not depend on the temperature
collision theory states that particles will react when they ___ with each other. for a reaction to be successful, the particles must have enough ___ energy
- collide - kinetic
reaction rate is expressed as a change in the ___ of reactants or products as a function of ___
- concentration - time
starting with only reactants, during the course of a reaction, reactant concentrations ___ and product concentrations ___
- decrease - increase
for a collision to be effective, the colliding particles must have enough ___ and the appropriate molecular ___
- energy - orientation
select all the statements that correctly describe enzymes
- enzymes are biological catalysts - an enzyme is typically a large protein molecule that contains one or more active sites where interactions with substrates take place - enzymes can increase the rate of biochemical reactions by factors ranging from 10^6 to 10^10
select all of the following statements that correctly describe experimental support for reaction mechanisms
- experiments are used to determine whether or not a proposed reaction mechanism is plausible - isotope labelling experiments can be used to distinguish between different possible reaction schemes
match the order of the reaction with the information provided about the effect of changing [A] for the reaction A -> products - if the rate doubles when [A] doubles, the reaction is - if the rate quadruples when [A] doubles, the reaction is - if the rate doesn't change when [A] doubles, the reaction is
- first order with respect to A - second-order with respect to A - zero order with respect to A
what may be included in a reaction mechanism?
- formation of a new species that does not appear in the overall reaction - bond-making steps - a catalyst - bond-breaking steps
select all the statements that correctly describe homogeneous catalysts
- homogeneous catalysts can be designed to function selectively - homogeneous catalysts are dispersed in a single phase with the reactants
what are common advantages of homogeneous catalysts?
- homogeneous catalysts commonly cost less than the alternative heterogeneous catalysts (precious metals) - homogeneous catalysts can be designed to function selectively for particular types of reactions - reactions including homogeneous catalysts can often be carried out under atmospheric conditions; using atmospheric conditions reduces production costs and minimizes the decomposition of products at high temperatures - homogeneous catalysts are often difficult to recycle and reuse as they often remain in the reaction mixture and are therefore not ideal for use in industrial process
which of the following statements correctly relate experimental observations with reaction order?
- if [A] is decreased to one-half of its original value and the reaction rate is halved, the reaction is first order with respect to A - if [A] is doubled and the reaction rate increases by a factor of 4, the reaction is second order with respect to A
which of the following options correctly interpret the rate law rate = k[Hs][NO]^2?
- if [NO] is doubled while [H2] remains the same, the reaction will occur 4 times faster; if [NO] is doubled the reaction rate will increase by 2^2 since the reaction is second order in NO - the reaction is second order with respect to NO
which of the following statements correctly describe how a rate law is determined?
- if there is more than one reactant present the reaction orders will usually be determined individually - the rate law is determined by measuring the initial reaction rate for different reactant concentrations - the value of k can be calculated from a single experiment once the reaction orders are known
which of the following options correctly describe instantaneous rate?
- instantaneous rate is equal to the slope of a tangent to the curve of a concentration vs. time plot at any particular time - instantaneous rate is the rate for a specific instant in time
match each type of elementary reaction to the correct description - unimolecular elementary reaction - binary elementary reaction - termolecular elementary reaction
- one reactant molecule decomposes in a single reaction step - two reactant molecules collide in a single reaction step - three reactant molecules collide in a single reaction step
in the rate law rate = k[A]^x[B]^y, the exponents x and y are called the reaction ___. if x=1, the reaction is said to be ___ ___ with respect to reactant A.
- orders - first order
raising the temperature of a reaction increases the reaction rate by increasing the ___ and ___ of the collisions
- rate - energy
select all of the following rate laws where the rate constant k has units equal to M^-2 s^-1. all rates are represented with the units of Ms^-1
- rate = k[A][B][C] - rate = k[A]^3 - rate = k[A]^2[B]
H2O2 (aq) decomposes rapidly in the presence of iodide ion (I^-). select all the statements that correctly interpret the experimental data provided for this reaction initial [H2Os] (M): initial [I^-] (M): initial rate (M/s): 1.0*10^-2 2.0*10^-2 2.3*10^7 1.0*10^-2 4.0*10^-2 4.6*10^7 3.0*10^-2 2.0*10^-2 6.9*10^7
- rate = k[H2O2][I^-] - the reaction is first order with respect to I^-; the reaction rate doubles when [I^-] doubles. the reaction is therefore first order with respect to I^-
for the reaction aA + bB -> cC + dD, the rate law is rate = k[A]^x[B]^y. match the appropriate definition with each term of the rate law - k - x, y - [A], [B]
- rate constant - reaction orders - reactant concentrations
match each symbol used in the reaction steps of general enzyme kinetics (shown) to the correct description - k1 - k-1 - k2
- rate constant for the formation of the enzyme-substrate intermediate - rate constant for the decomposition of the enzyme-substrate intermediate to the enzyme and substrate - rate constant for the decomposition of the enzyme-substrate intermediate to the enzyme and product
which of the following statements correctly describe the rate of reaction?
- rate of reaction = 1/coefficient *change in concentration[product]/change in time, where the coefficient is the number in front of the product in the balanced chemical equation - rate of reaction avoids reporting the rate of disappearance or appearance of a specific chemical species in a reaction
the mechanism of heterogeneous catalysis is proposed to occur in a series of steps - adsorption - activation - reaction - desorption
- reactant molecules bind to the surface of the solid catalyst - reactant molecules become oriented such that reaction is possible - bond-breaking and/or bond-making step(s) occur - product molecules leave the solid catalyst surface
match each symbol used on the potential energy profile for a two-step reaction (shown) to the correct description - R - P - Ea (step 1) - Ea (step two) - difference in potential energy between R and P
- reactants - products - the activation energy of the rate-determining step - the activation energy of the fast step - thermodynamics (change of E) of overall reaction; the larger the activation energy (Ea), the slower the step
which of the following statements correctly describe the relationship between reaction rate and concentrations of reactants and products?
- reactants (or products) with large coefficients have relatively high rates of disappearance (or appearance) - reactants (or products) with the same coefficient have the same rates of disappearance (or appearance)
which of the following statements correctly describe reaction intermediates?
- reaction intermediates do not appear in the overall equation for the reaction - reaction intermediates are formed and used up over the course of a reaction
the following sets of conditions are measurements associated with a reaction occurring at different temperatures. the rate law for the reaction 2A + 2B -> C + D is found to be rate = k[A]^2. rank the conditions in order of the value of the rate constant for the reaction with the highest value rate constant appearing at the top of the list
- reaction rate = 0.20 M/s; [A] = 0.010 M; [B] = 1.0 M - reaction rate = 0.040 M/s; [A] = 8.0*10^-3M; [B] = 0.50 M - reaction rate = 3.0 M/s; [A] = 0.50 M/s; [B] = 0.75 M
a(n) ___ registers the amount of visible light absorbed by a substance and can be used to determine reactant or product ___ at different times in a reaction such that an average ___ can be calculated
- spectrometer - concentration - rate
which of the following options correctly describe a difference between the potential energy profiles for an uncatalyzed and catalyzed reaction pathway (shown)?
- the activation energy in the reverse direction (products -> reactants) - the activation energy in the forward direction (reactants -> products) - the potential energies of the products do not change upon the addition of a catalyst - the potential energies of the reactants do not change upon the addition of a catalyst
which of the following statements correctly describe the average rate of a reaction?
- the average reaction rate generally decreases with time; reaction rate decreases as reactant concentrations decrease - average reaction rate expresses the decrease in reactant particles with time - for the reaction A -> B, the average reaction rate is expressed as [B]final - [B] initial/t final-t initial - reaction rates are always expressed as positive values
which of the following statements correctly describe the kinetics of an elementary step?
- the elementary step 2HI (g) -> H2 (g) + I2 (g) follows second-order kinetics; since this is an elementary step the reaction order is equal to the molecularity. 2 molecules of HI collide to form products. the reaction bimolecular and follows second-order kinetics. - the rate law for an elementary step can be deduced from its balanced equation - for an elementary step, reaction order equals molecularity
which of the following criteria must be met for a reaction mechanism to be considered valid?
- the elementary steps must add up to the overall balanced reaction - the mechanism must correlate with the experimentally determined rate law - the elementary steps must be physically reasonable
which of the following options correctly describe the different models of enzyme action?
- the enzyme forms the enzyme-substrate complex, which is then converted to product - the lock-and-key model proposes that the active site of an enzyme provides a precise fit for its substrate - the enzyme active site can modify its shape to a certain extent to accommodate different substrates
which of the following options correctly describe the half-life of a second-order reaction?
- the half-life of a second-order reaction is inversely proportional to the initial reactant concentration - the half-life of a second-order reaction is related to the rate constant - the half-life of a first-order reaction is a constant value, but for a second-order reaction it varies inversely as a function of the initial reactant concentration
which of the following statements correctly describe initial rate of the use of initial rate?
- the initial rate is an instantaneous rate - initial rate is commonly measured at different reactant concentrations in order to determine a rate law for a reaction - initial rate is an instantaneous rate measured at the beginning of the reaction
the rate law for the reaction NO2 (g) + CO (g) -> NO (g) + CO2 (g) is given by rate = k[NO2]^2. consider the mechanism depicted in the illustration. which options correctly describe the validity of this mechanism? 1. 2NO2 (g) -> N2 (g) + 2O2 (g) [slow] 2. 2CO (g) + O2 (g) -> 2CO2 (g) [fast] 3. N2 (g) + O2 (g) -> 2NO (g) [fast]
- the mechanism does agree with the experimental rate law - the elementary steps add up to the overall balanced equation; the sum of the elementary steps gives an equation that is equal to the overall balanced equation when divided by 2
which of the following factors are affected by an increase in reactant concentration
- the number of reactant collisions - the number of reactant particles in a given volume - the rate of reaction
match each rate law with the statement that correctly describes it - rate = k[Br][BrO3][H^+]^2 - rate = k[O3]^2[O2]^-1 - rate = k[NO]^2[O2] - rate = k[NH3]^0
- the overall reaction order is 4 - the overall reaction order is one - the rate is first order with respect to O2 - the rate is not dependent on the reactant concentrations
which of the following statements correctly describe the rate constant K for a reaction?
- the rate constant has a constant value for a given reaction at a constant temperature - the rate constant relates reaction rate to reactant concentration - the value of k is not affected by reactant concentration
select all the statements that correctly describe the rate-determining step of a reaction mechanism
- the rate-determining step is the slowest step in a reaction mechanism - the rate of an overall reaction is determined by the rate of the rate-determining step in a reaction mechanism - the rate law for an overall reaction is based on the rate-determining step
which of the following statements describe an integrated rate law?
- the reactant concentration at any time in the reaction can be determined from the integrated rate law - the value of the reaction constant, k, can be determined using an integrated rate law - an integrated rate law included time as a variable
select all the statements that correctly interpret the experimental data provided for the reaction: 2A + B2 -> 2AB initial [A] (M): initial [B2] (M): initial rate (M/s) 0.15 0.10 2.2*10^-3 0.30 0.10 4.3*10^-3 0.15 0.20 8.8*10^-3
- the reaction is second order with respect to [B2] - the overall reaction order is 3 - the reaction is first order with respect to A
which of the following options correctly describe an effect of increasing temperature on a reacting system?
- the reaction rate increases - particles collide more energetically - particles collide more frequently - with some very rare exceptions, the reaction rate virtually always increases as temperature increases; both the frequency and proportion of effective collisions will increase when temperature increases
which of the following statements correctly describe a zero-order reaction?
- the reaction rate is independent of the reactant concentration - when [A] is plotted against t, a straight line results
select all the statements that correctly describe a reaction mechanism
- the sequence of steps that sum to give the overall reaction is called the reaction mechanism - a reaction mechanism helps to depict how a reaction actually takes place through showing each bond-breaking and bond-making step
which of the following statements correctly describe the transition state of a reaction?
- the transition state species is highly unstable; the transition state is a temporary species formed as the result of an effective collusion. it exists for a very short time - the transition state only exists at the instant of highest potential energy in the reaction
in the reaction A + B -> AB -> C + D, AB is a high-energy, temporary species formed by the reactant molecules. AB is called the ___
- transition state - activated complex
which question(s) can be answered from an integrated rate law that cannot be answered by other forms of the rate law?
- what is [A] after y minutes of the reaction - how long will it take to use up x moles per liter of A
which of the following options correctly describe the principles of collision theory
- when particles collide, some of their kinetic energy is converted to vibrational energy - collision theory states that in general particles must collide in order to react - reaction rate is directly proportional to the number of collisions per second
match each reaction order with the x and y parameters that generate a linear plot. ([A] represents the concentration of reactant A) - zero order - first order - second order
- x=time; y=[A] - x=time; y=ln[A] - x=time; y=1/[A]
which option correctly expresses the rate of the reaction below in terms of the change in concentration of each reactant and product? A (g) + 2B (g) -> C (g)
-change in concentration [A]/change in temperature = -1/2 change in concentration[B]/change in temperature = change in concentration [C]/change in temperature
solve for the rate constant k given the following information for the first-order reaction represented by A -> products time (s): [A] (M): rate (M/s): 0.0 0.0250 4.5*10^-4 25 0.0180 3.2*10^-4 50 0.0078 1.4*10^-4
0.0018s^-1; at any given instant, rate = k[A] so k = rate/[A]
the reaction AB (g) -> A (g) + B (g) follows second-order kinetics. if k = 0.200 L/mol*s and [ABB]o = 1.50M, what is the concentration of AB after 10.0s?
0.375 M
how long does it take for the concentration of a reactant in a first-order reaction to decrease to 50% of the initial concentration, if the rate constant is equal to 1.00s^-1
0.69s
correctly order the steps necessary to assess the validity of the mechanism shown, if the observed rate law is rate = k[A][B][C] 1. A (g) + B (g) -> X (g) [fast] 2. X (g) + C (g) -> Y (g) [slow] 3. Y (g) -> D (g)
1. fast step: rate = k[A][B] and rate = k[X] slow step: rate = k2[X][C]; the rate of a reaction is determined by its slowest step. analyze the slowest step and steps that precede it 2. [X] = k1/k-1 [A][B] 3. rate = k2k1/k-1 [A][B][C] or k[A][B][C]; the rate for the slowest step is rewritten in terms of [reactants]. the rate law matches the observed rate law
calculate the activation energy for the reaction 2NOCl (g) -> 2NO (g) + Cl2 (g), if the rate constant k is equal to 0.286 L/mol*s at 500. K and 0.175 L/mol*s at 490. K
1.00 * 10^2 kJ/mol
solve for the rate constant k for the first-order reaction A (g) -> products given the following data: time (s): Pa (mmHg): 0 250. 10 220. 50 132
1.3*10^-2s^-1
which of the following plots will give a straight line for a reaction that follows second-order kinetics?
1/[A] vs time
which of the following options gives the correct expression for the integrated rate law for a reaction that follows second-order kinetics? the reactant is represented by the equation A -> products
1/[A]t = kt + 1/[A]o
at 25 degrees celsius, HI breaks down very slowly to form H2 and I2. the reaction follows second-order kinetics and k at 25 degrees celsius is 2.4*10^-21 L/mol*s. if 0.0100 mol of HI (g) is placed in a 1.0 L container, how long will it take for the concentration of HI to reach 0.00900 mol/L?
4.6*10^21s; (1/[A]t-1/[A]o)/k = t
for the reaction 2BH3 (g) -> B2H6 (g), calculate the rate constant for the reaction if the rate when [BH3] = 0.10M is found to be 5.0*10^-4 M/s. under the conditions studied the reaction is known to be first order in BH3 (g)
5.0*10^-3s^-1
iodine-23 breaks down in a first-order process with a half-life of 13.1 h. what is the rate constant for this process?
5.29*10^-2 h
which term represents the frequency factor in the arrhenius equation? k = Ae ^Ea/RT
A
which equation correctly relates the pressure of a gas A (Pa) to the concentration of gas A ((A))
[A] = Pa/RT
the ___ energy of a reaction is the energy threshold that colliding molecules must exceed in order to react
activation
which of the following statements best describes the effect of reactant concentration on reactant rate?
as reactant concentration increases, the number of reactant collisions increases, which in turn increases the reaction rate
a ___ is a substance that increases the rate of a reaction without being consumed. this type of substance is often used up and regenerated during the reaction
catalyst
in the arrhenius equation (shown), the factor A is related to the ___ of collisions between particles that result in a chemical reaction k = Ae ^-Ea/RT
frequency
what type of reaction rate is typically used to find other kinetic parameters?
initial rate; since the rate of reaction generally changes over time, using an average rate may lead to errors in other kinetic parameters
a reaction ___ is a species that is formed and then used up during the course of a reaction
intermediate
which one of the following options represents the arrhenius equation expressed as a linear equation
ln k = (- Ea/R)(1/T) + ln A
which of the following is the integrated form of a first-order rate law for the reaction A -> products?
ln[A]t = -kt + ln[A]o
the experimentally determined rate law for the overall reaction (2A + B2 -> A2B2) is: rate = k[A][B2]. a student proposed the following reaction mechanism. what makes this mechanism not plausible A + B2 -> AB2 slow 2A + B2 -> A2B2 fast
the mechanism shown is not consistent with the overall reaction; the slow step is first order in A and first order in B2, which is consistent with the experimentally determined rate law
true or false: the rate law for an elementary step can be deduced from its reaction stoichiometry
true; since an elementary reaction occurs in one step, its rate law can be deduced from the reaction stoichiometry
true or false: the calculated rate of a reaction usually depends on the time interval chosen
true; since the rate of a reaction generally decreases over time, average rates will differ depending on the specific time interval
if the rate law for a certain reaction is given by rate = k[A]^x[B]^y, the overall reaction order for the reaction is equal to ___
x+y; the reaction order is the sum of the powers to which all reactant concentrations appearing in the rate law are raised