Deck 20: Chemical Kinetics

Question 1

If the rate of a specific chemical reaction is independent of the concentrations of the reactants,the reaction is zero order.

Answer 1

True

Question 2

For the reaction: C₂H₄Br₂ + 3 KI → C₂H₄ + 2 KBr + KI₃,when the rate of disappearance of C₂H₄Br₂ is 2.0 × 10^-5 M/s,what is the rate of appearance of KBr?

A)0.67 × 10^-5 M/s
B)2.0 × 10^-5 M/s
C)4.0 × 10^-5 M/s
D)6.0 × 10^-5 M/s
E)1.0 × 10^-5 M/s

Answer 2

4.0 × 10^-5 M/s

Question 3

Adding a catalyst lowers the activation energy of a reaction.

Answer 3

True

Question 4

For the reaction: 2 N₂O₅(g)→ 4 NO₂(g)+ O₂(g)at the time when N₂O₅ is being consumed at a rate of 1.2 × 10^-4 M/s,what is the rate at which O₂ is being formed?

A)1.2 × 10^-4 M/s
B)2.4 × 10^-4 M/s
C)6.0 × 10^-5 M/s
D)3.0 × 10^-5 M/s
E)4.8 × 10^-4 M/s

Question 5

If a reaction has a rate equation of rate = k[A][B][C] then it is:

A)overall second order
B)overall first order
C)overall third order
D)zero order in A
E)second order in B

Question 6

For the reaction: C₂H₄Br₂ + 3 KI → C₂H₄ + 2 KBr + KI₃,when the rate of disappearance of C₂H₄Br₂ is 2.0 × 10^-5 M/s,what is the rate of disappearance of KI?

A)0.67 × 10^-5 M/s
B)2.0 × 10^-5 M/s
C)4.0 × 10^-5 M/s
D)6.0 × 10^-5 M/s
E)1.0 × 10^-5 M/s

Question 7

For the reaction: C₂H₄Br₂ + 3 KI → C₂H₄ + 2 KBr + KI₃,when the rate of disappearance of C₂H₄Br₂ is 2.0 × 10^-5 M/s,what is the rate of appearance of C₂H₄?

A)0.67 × 10^-5 M/s
B)2.0 × 10^-5 M/s
C)4.0 × 10^-5 M/s
D)6.0 × 10^-5 M/s
E)1.0 × 10^-5 M/s

Question 8

A heterogeneous catalyst is a catalyst that is in two phases of matter.

Question 9

The reaction has the rate law Rate = k[A][B]².Which will cause the rate to increase the most?

A)doubling [A]
B)lowering temperature
C)tripling [B]
D)quadrupling [A]
E)doubling [B]

Question 10

Define rate law.

A)A theoretical equation that describes how the rate of reaction depends on the concentration of reactants.
B)An experimentally determined equation that describes how the rate of reaction depends on the concentration of reactants.
C)A theoretical equation that describes how the rate of reaction depends on temperature,orientation and number of collisions.
D)An experimentally determined equation that describes how the rate of reaction depends on temperature,orientation and number of collisions.
E)A statement that describes how the ratio of reaction depends on concentration of reactants developed from the balanced equation.

Question 11

If the half-life of a reactant is independent of its initial concentration,the reaction order is 0.

Question 12

Temperature has no effect on reaction rate.

Question 13

For the reaction: C₂H₄Br₂ + 3 KI → C₂H₄ + 2 KBr + KI₃,when the rate of appearance of C₂H₄ is 2.0 × 10^-5 M/s,what is the rate of disappearance of C₂H₄Br₂?

A)0.67 × 10^-5 M/s
B)2.0 × 10^-5 M/s
C)4.0 × 10^-5 M/s
D)6.0 × 10^-5 M/s
E)1.0 × 10^-5 M/s

Question 14

If increasing the concentration of A in a chemical reaction causes no increase in the rate of the reaction,then we may say the reaction rate is first order in [A].

Question 15

For a reaction with a second order rate constant,the correct unit is M ∙ time^-1.

Question 16

Energy of activation has no effect on reaction rate.

Question 17

In the Arrhenius equation,ln k = ^-E_a/RT + ln A,the symbol A denotes the initial concentration of A.

Question 18

For the reaction: 2 N₂O₅(g)→ 4 NO₂(g)+ O₂(g)the rate law is:
= k[N₂O₅]
At 300 K,the half-life is 2.50 × 10⁴ seconds and the activation energy is 103.3 kJ/mol O₂.At the time when N₂O₅ is being consumed at a rate of 1.2 × 10^-4 M/s,what is the rate at which NO₂ is being formed?

A)1.2 × 10^-4 M/s
B)2.4 × 10^-4 M/s
C)6.0 × 10^-5 M/s
D)3.0 × 10^-5 M/s
E)4.8 × 10^-4 M/s

Question 19

In the reaction C₄H₉Cl(aq)+ H₂O(l)→ C₄H₉OH(aq)+ HCl(aq)the concentration of the reactant changes from 0.0562 M to 0.0431 M in 85 sec.What is the average rate of decomposition over this interval?

A)1.54 × 10^-4 M/s
B)1.54 × 10^-4 moles
C)1.54 × 10^-4 moles/s
D)0.0154 M
E)0.0154 M/s

Question 20

In the Arrhenius equation,ln k = ^-E_a/RT + ln A,the symbol A is a constant that represents the frequency of collisions with the proper orientation and other steric conditions favorable for a reaction.

Question 21

Which of the following is FALSE for a second order reaction?

A)1/[A]_t - 1/[A]_o = kt.
B)t_1/2 = 1/k[A]_o.
C)If 1/[A] versus time is a straight line,the reaction is second order.
D)Each successive half-life is 4 times as long as the previous.
E)The slope of 1/[A]_t versus time is k.

Question 22

In a second order reaction:
I.the sum of the exponents in the rate law is equal to two.
II.at least one of the exponents in the rate law is a two.
III.the half-life is dependent on the initial concentration of the reactant species.
IV.the half-life is independent of the initial concentration of the reactant species.
V.k can be expressed as M^-2s^-1 or M^-2min^-1.

A)I and IV
B)II and IV
C)I,III,and V
D)I and III
E)II and III

Question 23

For a reaction Rate = k[A][B]²,what factor will keep k unchanged?

A)raising temperature
B)adding inhibitor
C)increasing [A]
D)adding catalyst

Question 24

Data for the reaction A + B → C are given below.Find the rate constant for this system.

A)2.8 × 10^-2 M^-1s^-1
B)2.8 × 10^-2 Ms^-1
C)2.8 × 10^-2 M²s^-1
D)1.7 × 10^-3 M^-1s^-1
E)1.7 × 10^-3 Ms^-1

Question 25

The reaction A + B → C + D is second order in A and zero order in B.The value of k is 0.012 M^-1 min^-1.What is the rate of this reaction when [A] = 0.125 M and [B] = 0.435 M?

A)5 × 10^-4 M min^-1
B)3.4 × 10^-3 M min^-1
C)1.3 M min^-1
D)1.9 × 10^-4 M min^-1
E)1.5 × 10^-3 M min^-1

Question 26

Which of the following has no effect on the rate of a reaction?

A)value of ΔH°
B)activation energy
C)presence of a catalyst
D)temperature of reactants
E)concentrations of reactants

Question 27

Activation energy is:

A)energy at the bottom of the reaction curve
B)the heat energy in joules required to break the bonds in one reactant
C)an energy that a catalyst brings to the system to activate one of the reactants
D)the kinetic energy of solution stirring that brings the reaction to start
E)minimum kinetic energy that molecules must bring to their collisions for a chemical reaction to occur

Question 28

Choose the INCORRECT statement.

A)A reaction intermediate is produced and used up during the reaction.
B)A transition state and a reaction intermediate are the same.
C)An activated complex has partially formed bonds.
D)A reaction intermediates have fully formed bonds.
E)The rate-determining step is the slow-step.

Question 29

Which of the following statements is correct?

A)A zero order reaction depends on the concentration of reactants.
B)A reaction rate cannot be calculated from the collision frequency alone.
C)The activated complex is a chemical species that can be isolated and analysed.
D)The number of collisions has no effect on the rate constant.
E)The orientation of a collision does not affect the rate constant.

Question 30

For the second order reaction A → products,the following data are obtained:
[A] = 1.512 M,t = 0 min
[A] = 1.490 M,t = 1.0 min
[A] = 1.469 M,t = 2.0 min
What is the rate constant,k,for the reaction?

A)3.6 × 10^-3 M^-1 min^-1
B)1.4 × 10^-2 M^-1 min^-1
C)2.2 × 10^-2 M^-1 min^-1
D)1.0 × 10^-2 M^-1 min^-1
E)9.7 × 10^-3 M^-1 min^-1

Question 31

Which of the following statements is INCORRECT?

A)Radioactive decay is a first order reaction.
B)Half-life in a first order reaction is constant.
C)For a first order reaction ln [A]_t/[A]_o = kt.
D)In gaseous reactions [A] can be expressed as concentration or as pressure.
E)In a zero order reaction the rate remains constant throughout the reaction.

Question 32

For the reaction 2 HgCl₂ + C₂O₄^2- → products,data are:

The rate law is Rate = k[HgCl₂]^x[C₂O₄^2-]^y. Thus:

A)x = 2,y = 1
B)x = 2,y = 2
C)x = 1,y = 2
D)x = 1,y = 1
E)x = 0,y = 2

Question 33

For the second order reaction A → products,the following data are obtained:
[A] = 3.024 M,t = 0 min
[A] = 2.935 M,t = 1.0 min
[A] = 2.852 M,t = 2.0 min
What is the rate constant,k?

A)3.6 × 10^-3 M^-1 min^-1
B)1.4 × 10^-2 M^-1 min^-1
C)2.2 × 10^-2 M^-1 min^-1
D)9.7 × 10^-3 M^-1 min^-1
E)1.0 × 10^-2 M^-1 min^-1

Question 34

The rate of a specific chemical reaction is independent of the concentrations of the reactants.Thus the reaction is:

A)first order in A
B)second order
C)first order in the product
D)catalyzed
E)overall zero order

Question 35

Choose the INCORRECT answer.The rate of a chemical reaction:

A)usually is increased when the concentration of one of the reactants is increased
B)is dependent on temperature
C)may be increased by certain catalytic agents
D)will be very rapid if the activation energy is large
E)describes the rate of change in concentration of a reactant or product with time

Question 36

For 2 NO + O₂ → 2 NO₂,initial rate data are:

The rate law is Rate = k[NO][O₂]^y:

A)x = 1,y = 2
B)x = 2,y = 1
C)x = 1,y = 1
D)x = 2,y = 2
E)x = 0,y = 2

Question 37

If increasing the concentration of A in a chemical reaction 2 A → B + C causes no increase in the rate of the reaction,then we may say:

A)A is a catalyst
B)the reaction rate is zero order in A
C)the reaction rate is zero order in [A]
D)the reaction rate is first order in [A]
E)A is not involved in the reaction

Question 38

Calculate rate constant k for a first order reaction with a half-life of 75.0 min.

A)52.0 min^-1
B)1.54 × 10^-4 min^-1
C)1.33 × 10^-2 min^-1
D)9.24 × 10^-3 min^-1
E)2.67 × 10^-2 min^-1

Question 39

In the first order reaction A → products,[A] = 0.400 M initially and 0.250 M after 15.0 min,what will [A] be after 175 min?

A)1.67 × 10^-3 M
B)1.04 × 10^-3 M
C)3.70 × 10^-2 M
D)6.024 × 10^-3 M
E)2.31 × 10^-1 M

Question 40

Which of the following statements is true about the reaction 2 A → B + C which is first order in A and first order overall?

A)The rate of the reaction will decrease at higher concentrations of B and C.
B)The time required for one half of A to react is directly proportional to the quantity of A.
C)The rate of formation of C is twice the rate of reaction of A.
D)The rate of formation of B is the same as the rate of reaction of A.
E)The initial rate doubles with doubling of initial concentration of A.

Question 41

Define activation energy.

A)the difference between the energy of the products and reactants
B)the energy difference between the maximum energy of reaction and the energy of the products
C)the minimum total kinetic energy that molecules must bring to their collisions for a chemical reaction to occur
D)the total kinetic energy of molecules in collisions
E)the total kinetic energy of molecules in a system

Question 42

A catalyst alters the rate of a chemical reaction by:

A)always providing a surface on which molecules react
B)changing the products formed in the reaction
C)inducing an alternate pathway for the reaction with generally lower activation energy
D)changing the frequency of collisions between molecules
E)increasing the number of collisions of molecules

Question 43

Activation energy is:
I.the minimum kinetic energy required for each molecule in a collision to produce a reaction.
II.the minimum total kinetic energy required for the molecules in a collision to produce a reaction.
III.a factor in determining the rate of a reaction.
IV.high for fast reactions.

A)I and III
B)I,III,and IV
C)II,III
D)II and IV
E)II,III,and IV

Question 44

What is the rate law for the following mechanism?
N₂O + NO → N₂ONO (Slow)
N₂ONO → N₂ + NO₂ (Fast)

A)Rate = k[N₂O]
B)Rate = k[NO]
C)Rate = k[N₂O][NO]
D)Rate = k[N₂][NO₂]
E)Rate = k[N₂ONO]

Question 45

What is the rate law for the following reaction and its mechanism?
2 O₃ → 3 O₂ (overall reaction)
O₃ → O₂ + O∙ (slow)
O∙ + O₃ → 2 O₂ (fast)

A)Rate = k[O₃]
B)Rate = k[O₃]²
C)Rate = k[O₃]²/[O₂]
D)Rate = k[O₃]/[O₂]
E)Rate = k[O₃][O₂]

Question 46

For the reaction: 2 N₂O₅(g)→ 4 NO₂(g)+ O₂(g)the rate law is:
= k[N₂O₅]
At 300 K,the half-life is 2.50 × 10⁴ seconds and the activation energy is 103.3 kJ/mol.What is the rate constant at 310 K?

A)2.78 × 10^-5 s^-1
B)7.29 × 10^-6 s^-1
C)7.29 × 10^-8 s^-1
D)3.70 × 10^-5 s^-1
E)1.05 × 10^-4 s^-1

Question 47

For the reaction: 2 N₂O₅(g)→ 4 NO₂(g)+ O₂(g)the rate law is:
= k[N₂O₅]
At 300 K,the half-life is 2.50 × 10⁴ seconds and the activation energy is 103.3 kJ/mol.What is the rate constant at 350 K?

A)4.78 s^-1
B)2.79 × 10^-5 s^-1
C)6.38 × 10¹⁶ s^-1
D)7.47 × 10^-8 s^-1
E)1.03 × 10^-2 s^-1

Question 48

Why is rate = k[HgCl₂] ²[C₂O₄^2-] not the rate law for the following mechanism?
2 HgCl₂ + C₂O₄^2- → 2 Cl^- + 2 CO₂ + Hg₂Cl₂ (overall reaction)
HgCl₂ + C₂O₄^2- ⇌ HgCl₂C₂O₄^2- (fast)
HgCl₂C₂O₄^2- + C₂O₄^2- → Hg + 2 C₂O₄Cl^2- (slow)
Hg + HgCl₂ → Hg₂Cl₂ (fast)
2 C₂O₄Cl^2- → C₂O₄^2- + 2 Cl^- + 2 CO₂ (fast)

A)The rate law is not based on the slow step of the proposed mechanism.
B)The steps do not add to the overall reaction.
C)The rate law does not agree with the overall reaction.
D)The exponents of HgCl₂ and C₂O₄^2- are not equal.
E)The first step is not the slow step.

Question 49

Which of the following lowers the activation energy of a reaction?

A)adding reactants
B)lowering the temperature
C)removing products
D)adding a catalyst
E)raising the temperature

Question 50

What is the rate constant at 305 K for the reaction:
2 N₂O₅ → 2 N₂O₄ + O₂,
If k = 3.46 × 10^-5 s^-1 at 298 K and E_a = 106 kJ/mol?

A)2.4 × 10^-5 s^-1
B)4.8 × 10^-5 s^-1
C)6.0 × 10^-5 s^-1
D)1.2 × 10^-5 s^-1
E)9.2 × 10^-5 s^-1

Question 51

Which is a plausible mechanism for the following reaction if the rate law is
2 O₃ → 3 O₂

A)2 O₃ → O₂ + O₄ (slow)
O₄ → 2 O₂ (fast)
B)2 O₃ → O₆ (slow)
O₆ → O₄ + O₂ (fast)
O₄ → 2 O₂ (slow)
C)2 O₃ → O₄^- + O₂⁺ (slow)
O₄^- → O₂ + O₂^- (fast)
O₂^- + O₂⁺ → 2 O₂ (slow)
D)O₃ ⇌ O₂ + O∙ (fast)
O∙ + O₃ → 2 O₂ (slow)
E)O₃ ⇌ O₂⁺ + O^- (fast)
O^- + O₃ → O₂ + O₂^- (slow)
O₂^- + O₂⁺ → 2 O₂ (fast)

Question 52

What is the main difference between a Pt catalyst and an enzyme catalyst?

A)An enzyme has greater substrate specificity.
B)The Pt catalyst causes a faster reaction.
C)The enzyme causes a faster reaction.
D)A Pt catalyst is always a homogeneous catalyst.
E)A Pt catalyst is an enzyme.

Question 53

Which statement is INCORRECT?

A)Activation energy is always the same for forward and reverse reaction.
B)If the forward reaction is endothermic,the reverse will be exothermic.
C)In an endothermic reaction,activation energy is usually greater than the enthalpy.
D)An activated complex has higher energy than any molecule contributing to it.
E)The activated complex will be the highest on the energy profile.

Question 54

A factor that decreases the activation energy for a reaction:
I.decreases the rate constant
II.increases the rate constant
III.has no effect on the rate constant
IV.increases the product yield
V.might be a catalyst

A)I and IV
B)II and IV
C)I,IV,and V
D)IV and III
E)II and V

Question 55

What is the rate law for the following reaction and its mechanism?
2 HgCl₂ + C₂O₄^2- → 2 Cl^- + 2 CO₂ + Hg₂Cl₂ (overall reaction)
HgCl₂ + C₂O₄^2- ⇌ HgCl₂C₂O₄^2- (fast)
HgCl₂C₂O₄^2- + C₂O₄^2- → Hg + 2 C₂O₄Cl^2- (slow)
Hg + HgCl₂ → Hg₂Cl₂ (fast)
2 C₂O₄Cl^2- → C₂O₄^2- + 2Cl^- + 2 CO₂ (fast)

A)Rate = k[HgCl₂][C₂O₄^2-]
B)Rate = k[HgCl₂]²[C₂O₄^2-]
C)Rate = k[Hg₂Cl₂]
D)Rate = k[HgCl₂][C₂O₄^2-]²
E)Rate = k[HgCl₂]²[C₂O₄^2-]²

Question 56

For the reaction: 2 N₂O₅(g)→ 4 NO₂(g)+ O₂(g)the rate law is:
= k[N₂O₅]
At 300 K,the half-life is 2.50 × 10⁴ seconds and the activation energy is 103.3 kJ/mol.What is the half-life at 310 K?

A)2.49 × 10⁴ s
B)9.51 × 10⁴ s
C)9.51 × 10⁶ s
D)6.57 × 10³ s
E)1.87 × 10^-1 s

Question 57

Choose the INCORRECT statement.

A)The rate-determining step is always the first step.
B)A unimolecular process is one in which a single molecule dissociates.
C)A bimolecular process is one involving a collision of two molecules.
D)A reaction mechanism is a step-by-step detailed description of a chemical reaction.
E)An elementary process is a step in the mechanism.

Question 58

According to the collision theory in gaseous molecules,collision frequency is ________ and the rate of reaction is ________ because ________.

A)low,low,molecules are so far apart
B)high,high,each collision results in a reaction
C)low,low,molecules must collide before they can react
D)high,relatively low,only a fraction of the collisions lead to a reaction
E)low,high,molecules are moving so fast that each reaction causes many others

Question 59

What is the rate law for the following mechanism?
CH₃COOC₂H₅ + H₂O → CH₃COOC₂H₆⁺ + OH^- (slow)
CH₃COOC₂H₆⁺ → CH₃COOH + C₂H₅⁺ (fast)
C₂H₅⁺ + OH^- → C₂H₅OH (fast)

A)Rate = k[CH₃COOC₂H₅][H₂O]²
B)Rate = k[C₂H₅OH]
C)Rate = k[CH₃COOH]
D)Rate = k[CH₃COOC₂H₅]
E)Rate = k[CH₃COOC₂H₅][H₂O]

Question 60

In the Arrhenius equation,ln k = ^-E_a/RT + ln A,the symbol A denotes:

A)the initial concentration of A
B)the activation energy
C)the rate constant
D)a constant that represents the frequency of collisions with the proper orientation and other steric conditions favorable for a reaction
E)the absolute temperature

Question 61

If the half-life of a reaction depends on the concentration of the reactant,then the reaction cannot be ________ order.

A)second
B)zero
C)first
D)third

Question 62

A catalyst:
I.lowers activation energy
II.provides an alternate reaction pathway
III.is consumed in the reaction and therefore does not appear in the chemical equation of each mechanism
IV.speeds a reaction
V.is heterogeneous if it is in a different phase than the reactants

A)I,III,and IV
B)I,IV,and V
C)II,III,and IV
D)II and IV
E)I,II,IV,and V

Question 63

The first order reaction A → products has = 150 s.What percent of the sample remains unreacted after 300 s?

A)25%
B)50%
C)12.5%
D)0.0%
E)100%

Question 64

Which of the following situations involves a heterogeneous catalysis?

A)The catalyst is present in a different phase of matter than are the reactants and products.
B)The catalyst is in two different phases of matter.
C)The reactants and products are different phases of matter in a catalyzed reaction.
D)The catalyst,reactants,and products are all different phases of matter.
E)The catalyst changes phases during the reaction.

Question 65

Data for the reaction A + B → C are given below.What is the correct rate law?

A)k [A] [B]
B)k [A]² [B]
C)k [A]² [B]²
D)k [B]²
E)k[A]²

Question 66

The reaction 2 H₂ + NO → H₂O + 1/2N₂ is first order in H₂ and second order in NO.The rate law is ________.

A)k[H₂]²[NO]
B)k[H₂][NO]²
C)k[H₂]
D)k[H₂][NO]
E)k[H₂][NO]^-2

Question 67

For the reaction: C₂H₄Br₂ + 3 KI → C₂H₄ + 2 KBr + KI₃
Initial rate data at 60 °C are:

The rate law is ________.

A)rate = k[KI]
B)rate = k[C₂H₄Br₂]
C)rate = k[KI]²
D)rate = k[KI][C₂H₄Br₂]
E)rate = k[KI][C₂H₄Br₂]²

Question 68

The rate constant for a first-order reaction is k = 0.00073 s^-1.Determine the percent of reactant that has decomposed after 500 s.

A)69%
B)57%
C)37%
D)31%
E)43%

Question 69

What is the order of reaction for the following reaction: Rate = k[A]^-1/2 [B]^1/2?

A)first order
B)zero order
C)1/2 order
D)-1/2 order
E)second order

Question 70

Given the following initial rate data,calculate the specific rate constant.

A)1.9 M²/s²
B)1.9 M^-1 s^-1
C)3.6 M s^-1
D)1.1 × 10⁸ M²/s²
E)3.6 M² s^-1

Question 71

Given the following initial rate data,write the rate law expression.

A)k [A] [B]
B)k [A]² [B]²
C)k [A]² [B]
D)k [B]²
E)k [A]²

Question 72

If a reaction is first order with a rate constant of 5.48 × 10^-2/s,how long is required for 3/4 of the initial concentration of reactant to be used up?

A)25.3 s
B)36.5 s
C)6.3 s
D)18.2 s
E)50.6 s

Question 73

A reaction is first order.If its initial rate is 0.0200 M/s and 25.0 days later its rate is 6.25 × 10^-4 M/s,then its half-life is ________.

A)12.5 days
B)5.0 days
C)25.0 days
D)50.0 days
E)2.5 days

Question 74

If the half-life of a reactant is independent of its initial concentration,the reaction order is ________.

A)0
B)0.5
C)1
D)2
E)3

Question 75

The rate data from a chemical reaction shows that doubling the concentration of A with the concentration of B remaining constant causes the rate to increase by a factor of four.What is the reaction order for [A]?

A)0
B)0.5
C)1
D)2
E)3

Question 76

The rate constant at 160 °C for the first order decomposition of ore is 0.032/min.The half-life of the reaction is ________.

A)62.5 s
B)31.25 s
C)5000 s
D)111 s
E)1300 s

Question 77

Substance A decomposes by a first-order reaction.Starting initially with [A] = 2.00 M,after 150 min [A] = 0.50 M.For this reaction what is ?

A)150 min
B)37.5 min
C)75.0 min
D)15.0 min
E)300 min

Question 78

The correct units of the specific rate constant for a zero order reaction are ________.

A)L/mol s
B)s^-1
C)s
D)L²/mol² s
E)rate is a constant,so it has no units

Question 79

If a catalyst is added to a reaction:
I.the value of k is increased
II.the value of k is decreased
III.the rate is increased
IV.the rate is decreased
V.neither rate nor the constant are changed,only the order

A)I and IV
B)II and IV
C)II and III
D)I and III
E)V only

Question 80

In the first-order,reaction A → products,[A] = 0.400 M initially and 0.250 M after 15.0 min,what is the value of the rate constant,k?

A)3.06 min^-1
B)0.0136 min^-1
C)0.470 min^-1
D)7.05 min^-1
E)0.0313 min^-1