Deck 15: Chemical Kinetics

Question 1

Write a balanced reaction for which the following rate relationships are TRUE. Rate = - = =

A) 2 N₂O₅ → 4 NO₂ + O₂
B) 4 NO₂ + O₂ → 2 N₂O₅
C) 2 N₂O₅ → NO₂ + 4 O₂
D) NO₂ + O₂ → N₂O₅
E) N₂O_{5 →} NO₂ + O₂

Answer 1

2 N₂O₅ → 4 NO₂ + O₂

Question 2

Give the characteristic of a zero order reaction having only one reactant.

A) The rate of the reaction is not proportional to the concentration of the reactant.
B) The rate of the reaction is proportional to the square of the concentration of the reactant.
C) The rate of the reaction is proportional to the square root of the concentration of the reactant.
D) The rate of the reaction is proportional to the natural logarithm of the concentration of the reactant.
E) The rate of the reaction is directly proportional to the concentration of the reactant.

Answer 2

The rate of the reaction is not proportional to the concentration of the reactant.

Question 3

The reaction,2A + 2B → C + D,has a rate constant of 6.0 × 10^-3 M^-2 s^-1 at 0°C.The order of this reaction is

A) 1st.
B) 2nd.
C) 3rd.
D) 4th.
E) There is not enough information given to answer the question.

Answer 3

3rd.

Question 4

Determine the rate law and the value of k for the following reaction using the data provided. CO(g)+ Cl₂(g)→ COCl₂(g)[CO]_i (M)[Cl₂]_i (M)Initial Rate
0)25 0.40 0.696
0)25 0.80 1.97
0)50 0.80 3.94

A) Rate = 11 M^-3/2s^-1 [CO][Cl₂]^3/2
B) Rate = 36 M^-1.8s^-1 [CO][Cl₂]^2.8
C) Rate = 17 M^-2s^-1 [CO][Cl₂]²
D) Rate = 4.4 M^-1/2s^-1 [CO][Cl₂]^1/2
E) Rate = 18 M^-3/2s^-1 [CO]²[Cl₂]^1/2

Question 5

What are the units of k in the following rate law?
Rate = k[X][Y]²

A)
B)
C) M² s
D)
E)

Question 6

Given the following balanced equation,determine the rate of reaction with respect to [N₂]. N₂(g)+ 3 H₂(g)→ 2 NH₃(g)

A) Rate = +
B) Rate = -
C) Rate = +
D) Rate = -
E) It is not possible to determine without more information.

Question 7

What are the units of k in the following rate law?
Rate = k[X]²[Y]²

A)
B)
C) M² s
D)
E)

Question 8

What are the units of k in the following rate law?
Rate = k[X]⁰[Y]⁰

A)
B) Ms
C) M^-1s^-1
D)
E)

Question 9

Write a balanced reaction for which the following rate relationships are TRUE. Rate = = = -

A) N₂ + O₂ → N₂O
B) 2 N₂O → 2 N₂ + O₂
C) N₂O → N₂ + 2 O₂
D) N₂O → N₂ + O₂
E) 2 N₂ + O₂ → 2 N₂O

Question 10

What are the units of k in the following rate law?
Rate = k[X]

A)
B) Ms
C)
D)
E)

Question 11

Identify the methods used to monitor a reaction as it occurs in the reaction flask.

A) polarimeter
B) spectrometer
C) pressure measurement
D) all of the above
E) none of the above

Question 12

Given the following balanced equation,determine the rate of reaction with respect to [H₂]. N₂(g)+ 3 H₂(g)→ 2 NH₃(g)

A) Rate = +
B) Rate = -
C) Rate = +
D) Rate = -
E) It is not possible to determine without more information.

Question 13

Give the characteristic of a second order reaction having only one reactant.

A) The rate of the reaction is not proportional to the concentration of the reactant.
B) The rate of the reaction is proportional to the square of the concentration of the reactant.
C) The rate of the reaction is proportional to the square root of the concentration of the reactant.
D) The rate of the reaction is proportional to the natural logarithm of the concentration of the reactant.
E) The rate of the reaction is directly proportional to the concentration of the reactant.

Question 14

What is the overall order of the following reaction,given the rate law?
NO(g)+ O₃(g)→ NO₂(g)+ O₂(g)Rate = k[NO][O₃]

A) 1st order
B) 2nd order
C) 3rd order
D) 1 order
E) 0th order

Question 15

Give the characteristic of a first order reaction having only one reactant.

A) The rate of the reaction is not proportional to the concentration of the reactant.
B) The rate of the reaction is proportional to the square of the concentration of the reactant.
C) The rate of the reaction is proportional to the square root of the concentration of the reactant.
D) The rate of the reaction is proportional to the natural logarithm of the concentration of the reactant.
E) The rate of the reaction is directly proportional to the concentration of the reactant.

Question 16

What are the units of k in the following rate law?
Rate = k[X][Y]^1/2

A) M/s
B) M^-1s^-1
C) M^1/2s^-1
D) M^-1/2s^-1
E) M^-1s^-1/2

Question 17

What are the units of k in the following rate law?
Rate = k[X]²

A) Ms^-1
B) Ms
C) M^-1s^-1
D) M^-2s^-1
E) M²s^-1

Question 18

Given the following balanced equation,determine the rate of reaction with respect to [NH₃]. N₂(g)+ 3 H₂(g)→ 2 NH₃(g)

A) Rate = +
B) Rate = -
C) Rate = +
D) Rate = -
E) It is not possible to determine without more information.

Question 19

Given the following balanced equation,determine the rate of reaction with respect to [NOCl]. 2 NO(g)+ Cl₂(g)→ 2 NOCl(g)

A) Rate = -
B) Rate = +
C) Rate = -
D) Rate = -
E) It is not possible to determine without more information.

Question 20

What are the units of k in the following rate law?
Rate = k[X][Y]

A)
B) Ms
C)
D)
E)

Question 21

Determine the rate law and the value of k for the following reaction using the data provided. S₂O₈²⁻(aq)+ 3 I⁻(aq)→ 2 SO₄²⁻(g)+ I₃⁻(aq)[S₂O₈²⁻]_i (M)[I⁻]_i (M)Initial Rate
0)30 0.42 4.54
0)44 0.42 6.65
0)44 0.21 3.33

A) Rate = 120 M^-2s^-1 [S₂O₈²⁻]²[I⁻]
B) Rate = 36 M^-1s^-1 [S₂O₈²⁻][I⁻]
C) Rate = 86 M^-2s^-1 [S₂O₈²⁻][I⁻]²
D) Rate = 195 M^-3s^-1 [S₂O₈²⁻]²[I⁻]²
E) Rate = 23 M^-1/2s^-1 [S₂O₈²⁻][I⁻]^1/2

Question 22

The rate constant for the first-order decomposition of N₂O is 3.40 s^-1.What is the half-life of the decomposition?

A) 0.491 s
B) 0.204 s
C) 0.236 s
D) 0.424 s
E) 0.294 s

Question 23

Carbon-14 has a half-life of 5720 years and this is a first order reaction.If a piece of wood has converted 25% of the carbon-14,then how old is it?

A) 11440 years
B) 2375 years
C) 4750 years
D) 4290 years
E) 1430 years

Question 24

Determine the rate law and the value of k for the following reaction using the data provided. 2 NO(g)+ O₂(g)→ 2 NO₂(g)[NO]_i (M)[O₂]_i (M)Initial Rate (M^-1s^-1)
0)030 0.0055 8.55 × 10^-3
0)030 0.0110 1.71 × 10^-2
0)060 0.0055 3.42 × 10^-2

A) Rate = 57 M^-1s^-1[NO][O₂]
B) Rate = 3.8 M^-1/2s^-1[NO][O₂]^1/2
C) Rate = 3.1 × 10⁵ M^-3s^-1[NO]²[O₂]²
D) Rate = 1.7 × 10³ M^-2s^-1[NO]²[O₂]
E) Rate = 9.4 × 10³ M^-2s^-1[NO][O₂]²

Question 25

Which of the following represents the integrated rate law for a zeroth-order reaction?

A) = - kt
B) - = kt
C) [A]_t - [A]_o = - kt
D) k = Ae^(-Ea/RT)
E) = + lnA

Question 26

What data should be plotted to show that experimental concentration data fits a zeroth-order reaction?

A) ln[reactant] vs. time
B) 1/[reactant] vs. time
C) ln(k) vs. 1/T
D) ln(k) vs. E_a
E) [reactant] vs. time

Question 27

For a certain reaction,a plot of ln [A] vs.time gives a straight line with a slope of -1.46 s^-1 and a y-intercept of 4.30.What is the order of the reaction?

A) zeroth-order
B) first-order
C) second-order
D) third-order
E) not enough information is given to solve the problem

Question 28

Which of the following represents the integrated rate law for a first-order reaction?

A) = - kt
B) - = kt
C) [A]_t - [A]_o = - kt
D) k = Ae^(-Ea/RT)
E) = + lnA

Question 29

What data should be plotted to show that experimental concentration data fits a first-order reaction?

A) 1/[reactant] vs. time
B) [reactant] vs. time
C) ln[reactant] vs. time
D) ln(k) vs. 1/T
E) ln(k) vs. E_a

Question 30

What data should be plotted to show that experimental concentration data fits a second-order reaction?

A) ln[reactant] vs. time
B) [reactant] vs. time
C) ln(k) vs. 1/T
D) 1/[reactant] vs. time
E) ln(k) vs. E_a

Question 31

Determine the rate law and the value of k for the following reaction using the data provided. NO₂(g)+ O₃(g)→ NO₃(g)+ O₂(g)[NO₂]_i (M)[O₃]_i (M)Initial Rate
0)10 0.33 1.42
0)10 0.66 2.84
0)25 0.66 7.10

A) Rate = 1360 M^-2.5s^-1[NO₂]^2.5[O₃]
B) Rate = 227 M^-2.5s^-1[NO₂][O₃]^2.5
C) Rate = 43 M^-1s^-1[NO₂][O₃]
D) Rate = 430 M^-2s^-1[NO₂]²[O₃]
E) Rate = 130 M^-2s^-1[NO₂][O₃]²

Question 32

Carbon-14 has a half-life of 5720 years and this is a first order reaction.If a piece of wood has converted 75% of the carbon-14,then how old is it?

A) 11440 years
B) 2375 years
C) 4750 years
D) 4290 years
E) 1430 years

Question 33

Which of the following statements is FALSE?

A) The average rate of a reaction decreases during a reaction.
B) It is not possible to determine the rate of a reaction from its balanced equation.
C) The rate of zero order reactions are not dependent on concentration.
D) The half life of a first order reaction is dependent on the initial concentration of reactant.
E) None of the statements are false.

Question 34

Which of the following statements is FALSE?

A) The half life of a zero order reaction is dependent on concentration.
B) The half life of a second order reaction is not dependent on concentration.
C) The rate of second order reactions is dependent on concentration.
D) The rate of a first order reaction is dependent on concentration.
E) None of the statements are false.

Question 35

The second-order decomposition of HI has a rate constant of 1.80 × 10^-3 M^-1s^-1.How much HI remains after 27.3 s if the initial concentration of HI is 4.78 M?

A) 4.55 M
B) 0.258 M
C) 3.87 M
D) 2.20 M
E) 2.39 M

Question 36

The half-life for the second-order decomposition of HI is 15.4 s when the initial concentration of HI is 0.67 M.What is the rate constant for this reaction?

A) 1.0 × 10^-2 M^-1s^-1
B) 4.5 × 10^-2 M^-1s^-1
C) 9.7 × 10^-2 M^-1s^-1
D) 2.2 × 10^-2 M^-1s^-1
E) 3.8 × 10^-2 M^-1s^-1

Question 37

Which of the following represents the integrated rate law for a second-order reaction?

A) = - kt
B) - = kt
C) [A]_t - [A]_o = - kt
D) k = Ae^(-Ea/RT)
E) = + lnA

Question 38

The half life for the decay of radium is 1620 years.What is the rate constant for this first-order process?

A) 4.28 × 10^-4 yr^-1
B) 1.12 × 10^-4 yr^-1
C) 2.33 × 10^-4 yr^-1
D) 8.91 × 10^-4 yr^-1
E) 6.17 × 10^-4 yr^-1

Question 39

The first-order decomposition of cyclopropane has a rate constant of 6.7 × 10^-4 s^-1.If the initial concentration of cyclopropane is 1.33 M,what is the concentration of cyclopropane after 644 s?

A) 0.43 M
B) 0.15 M
C) 0.94 M
D) 0.86 M
E) 0.67 M

Question 40

The first-order decomposition of N₂O at 1000 K has a rate constant of 0.76 s^-1.If the initial concentration of N₂O is 10.9 M,what is the concentration of N₂O after 9.6 s?

A) 7.4 × 10^-3 M
B) 1.0 × 10^-3 M
C) 1.4 × 10^-3 M
D) 3.6 × 10^-3 M
E) 8.7 × 10^-3 M

Question 41

Which of the following is a rate law for a reaction that is first order with respect to oxygen?

A) rate = k [NO₂]
B) rate = k [NO₂]² [O₂}^1/2
C) rate = k [NO₂] [O₂}^1/2
D) rate = k [NO₂] [O₂}^1/2 [N₂]^1/2
E) rate = k [NO₂]² [O₂}

Question 42

The first-order decay of radon has a half-life of 3.823 days.How many grams of radon decomposes after 5.55 days if the sample initially weighs 100.0 grams?

A) 83.4 g
B) 16.6 g
C) 50.0 g
D) 36.6 g
E) 63.4 g

Question 43

The first-order rearrangement of CH₃NC is measured to have a rate constant of 3.61 × 10^-15 s^-1 at 298 K and a rate constant of 8.66 × 10^-7 s^-1 at 425 K.Determine the activation energy for this reaction.

A) 160. kJ/mol
B) 240. kJ/mol
C) 417 kJ/mol
D) 127 kJ/mol
E) 338 kJ/mol

Question 44

Derive an expression for a "1/4-life" for a first-order reaction.

A)
B)
C)
D)
E)

Question 45

A reaction has a rate constant of 6.0 × 10^-3 L² mol^-2 s^-1 at 10°C.If its activation energy is 84 kJ/mol,what is the value of the rate constant at 50°C?

A) 4.8 L²mol^-2s^-1
B) 0.50 L²mol^-2s^-1
C) 0.018 L²mol^-2s^-1
D) 8.2 × 10³ L²mol^-2s^-1
E) 0.84 L²mol^-2s^-1

Question 46

A reaction occurs via the following sequence of elementary steps.What is the rate law based on this reaction mechanism?
1^st step: A + B → 2C + D slow
2^nd step: C → E fast
3^rd step: D → 2F fast

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

Question 47

Identify the rate-determining step.

A) the slowest step
B) the faster step
C) the fast step
D) always the last step
E) always the second step

Question 48

If the activation energy for a given compound is found to be 42.0 kJ/mol,with a frequency factor of 8.0 × 10¹⁰ s^-1,what is the rate constant for this reaction at 298 K?

A) 2.9 × 10^-4 s^-1
B) 7.4 × 10^-4 s^-1
C) 1.4 × 10⁹ s^-1
D) 4.6 × 10 ⁵ s^-1
E) 3.5 × 10³ s^-1

Question 49

For a reaction,what generally happens if the temperature is increased?

A) A decrease in k occurs, which results in a faster rate.
B) A decrease in k occurs, which results in a slower rate.
C) An increase in k occurs, which results in a faster rate.
D) An increase in k occurs, which results in a slower rate.
E) There is no change with k or the rate.

Question 50

Given the following proposed mechanism,predict the rate law for the overall reaction. A₂ + 2B → 2AB (overall reaction)
Mechanism
A₂ ⇌ 2A fast
A + B → AB slow

A) Rate = k[A][B]
B) Rate = k[A₂][B]
C) Rate = k[A₂][B]^1/2
D) Rate = k[A₂]
E) Rate = k [A₂]^1/2[B]

Question 51

Which of the following statements is TRUE?

A) The rate constant does not depend on the activation energy for a reaction where the products are lower in energy than the reactants.
B) A catalyst raises the activation energy of a reaction.
C) Rate constants are temperature dependent.
D) The addition of a homogeneous catalyst does not change the activation energy of a given reaction.
E) None of the above are true.

Question 52

The first-order decay of radon has a half-life of 3.823 days.How many grams of radon remain after 7.22 days if the sample initially weighs 250.0 grams?

A) 4.21 g
B) 183 g
C) 54.8 g
D) 76.3 g
E) 67.5 g

Question 53

A reaction is found to have an activation energy of 38.0 kJ/mol.If the rate constant for this reaction is 1.60 × 10² M^-1s^-1 at 249 K,what is the rate constant at 436 K?

A) 2.38 × 10⁵ M^-1s^-1
B) 1.26 × 10³ M^-1s^-1
C) 7.94 × 10⁴ M^-1s^-1
D) 4.20 × 10⁵ M^-1s^-1
E) 3.80 × 10⁴ M^-1s^-1

Question 54

If the activation energy for a given compound is found to be 103 kJ/mol,with a frequency factor of 4.0 × 10¹³ s^-1,what is the rate constant for this reaction at 398 K?

A) 1.2 s^-1
B) 8.2 s^-1
C) 3.9 × 10¹⁰ s^-1
D) 1.7 × 10¹⁰ s^-1
E) 2.5 × 10⁷ s^-1

Question 55

A reaction occurs via the following sequence of elementary steps.What is the reaction intermediate?
1^st step: A + 2B → 2C
2^nd step: 2C → D

A) A
B) B
C) C
D) D
E) There is no intermediate.

Question 56

A reaction is found to have an activation energy of 108 kJ/mol.If the rate constant for this reaction is 4.60 × 10^-6 s^-1 at 275 K,what is the rate constant at 366 K?

A) 12 s^-1
B) 1.7 s^-1
C) 0.58 s^-1
D) 5.4 × 10^-5 s^-1
E) 1.9 × 10^-4 s^-1

Question 57

A reaction is followed and found to have a rate constant of 3.36 × 10⁴ M^-1s^-1 at 344 K and a rate constant of 7.69 M^-1s^-1 at 219 K.Determine the activation energy for this reaction.

A) 23.8 kJ/mol
B) 42.0 kJ/mol
C) 11.5 kJ/mol
D) 12.5 kJ/mol
E) 58.2 kJ/mol

Question 58

The second-order decomposition of NO₂ has a rate constant of 0.255 M^-1s^-1.How much NO₂ decomposes in 4.00 s if the initial concentration of NO₂ (1.00 L volume)is 1.33 M?

A) 1.8 mol
B) 0.85 mol
C) 0.48 mol
D) 0.77 mol
E) 0.56 mol

Question 59

Derive an expression for a "1/3-life" for a first-order reaction.

A)
B)
C)
D)
E)

Question 60

The first-order decomposition of N₂O₅ at 328 K has a rate constant of 1.70 × 10^-3 s^-1.If the initial concentration of N₂O₅ is 2.88 M,what is the concentration of N₂O₅ after 12.5 minutes?

A) 0.124 M
B) 0.805 M
C) 2.82 M
D) 0.355 M
E) 0.174 M

Question 61

In the hydrogenation of double bonds,a catalyst is needed.In the first step,the reactants must come into contact with a metal surface.This step is known as

A) adsorption.
B) diffusion.
C) reaction.
D) desorption.
E) none of the above.

Question 62

Given the following balanced equation,determine the rate of reaction with respect to [O₂]. 2 O₃(g)→ 3 O₂(g)

A) Rate = +
B) Rate = -
C) Rate = +
D) Rate = -
E) It is not possible to determine without more information.

Question 63

Given the following balanced equation,determine the rate of reaction with respect to [H₂]. N₂(g)+ 3 H₂(g)→ 2 NH₃(g)

A) Rate = +
B) Rate = -
C) Rate = +
D) Rate = -
E) It is not possible to determine without more information.

Question 64

Biological catalysts that increase the rates of biochemical reactions are known as

A) substrates.
B) inhibitors.
C) enzymes.
D) binders.
E) trumanettes.

Question 65

A graph of 1/[A] vs.t gives a straight line.What are the units of k for this system?

A) M s^-1
B) s^-1
C) M^-1 s^-1
D) M^-2 s^-1
E) M^-3 s^-1

Question 66

Identify an homogeneous catalyst.

A) SO₂ over vanadium (V) oxide
B) Pd in H₂ gas
C) Pt with methane
D) H₂SO₄ with concentrated HCl
E) N₂ and H₂ catalyzed by Fe

Question 67

The rate of disappearance of HBr in the gas phase reaction 2HBr(g)→ H₂(g)+ Br₂(g)
Is 0.301 M at 150°C.The rate of appearance of is ________ M .

A) 1.66
B) 0.151
C) 0.0906
D) 0.602
E) 0.549

Question 68

Identify an heterogeneous catalyst.

A) CFCs with ozone
B) Pd in H₂ gas
C) KI dissolved in H₂O₂
D) H₂SO₄ with concentrated HCl
E) H₃PO₄ with an alcohol

Question 69

The first-order decomposition of ammonium nitrate has a rate constant of 0.110 min^-1.If the initial concentration is 0.551 M,what is the concentration after 38.5 min?

A) 0.0372 M
B) 7.98 × 10^-3 M
C) 0.513 M
D) 0.221 M
E) 0.143 M

Question 70

The rate of disappearance of HBr in the gas phase reaction 2HBr(g)→ H₂(g)+ Br₂(g)
Is 0.190 M s^-1 at 150°C.The rate of appearance of H₂ is ________ M s^-1.

A) 2.63
B) 0.0950
C) 0.0361
D) 0.380
E) 0.0860

Question 71

Given the following balanced equation,determine the rate of reaction with respect to [O₂]. 2 SO₂(g)+ O₂(g)→ 2 SO₃(g)

A) Rate = -
B) Rate = +
C) Rate = -
D) Rate = +
E) It is not possible to determine without more information.

Question 72

Reaction rate can change with

A) temperature.
B) the addition of a catalyst.
C) reactant concentrations.
D) A and C.
E) A, B, and C.

Question 73

Given the following balanced equation,determine the rate of reaction with respect to [SO₃]. 2 SO₂(g)+ O₂(g)→ 2 SO₃(g)

A) Rate = -
B) Rate = +
C) Rate = -
D) Rate = -
E) It is not possible to determine without more information.

Question 74

A reaction has a rate constant of 4.61 × 10^-4 M^-1 s^-1 at 34°C,and a rate constant of 5.87 × 10^-3 M^-1 s^-1 at 67°C.What is the activation energy?

A) 104 kJ/mol
B) 92.6 kJ/mol
C) 35.1 kJ/mol
D) 67.0 kJ/mol
E) 79.3 kJ/mol

Question 75

The combustion of ethylene proceeds by the reaction C₂H₄(g)+ 3O₂(g)→2CO₂(g)+ 2H₂O(g)
When the rate of disappearance of O₂ is 0.28 M s^-1,the rate of appearance of CO₂ is ________ M s^-1.

A) 0.19
B) 0.093
C) 0.84
D) 0.42
E) 0.56

Question 76

A sample contains 1.46 g of Cobalt-55.After 2.00 days,0.219 g remains.What is the half-life?

A) 17.5 h^-1
B) 22.6 h^-1
C) 1.35 h^-1
D) 0.540 h^-1
E) 11.6 h^-1

Question 77

In the hydrogenation of double bonds,a catalyst is needed.In the last step,the reactants must escape from the surface into the gas phase.This step is known as

A) adsorption.
B) diffusion.
C) reaction.
D) desorption.
E) none of the above.

Question 78

Given the following balanced equation,determine the rate of reaction with respect to [SO₂]. 2 SO₂(g)+ O₂(g)→ 2 SO₃(g)

A) Rate = -
B) Rate = +
C) Rate = -
D) Rate = +
E) It is not possible to determine without more information.

Question 79

A reaction occurs via the following sequence of elementary steps.What is the rate law based on this reaction mechanism?
1^st step: A ⇌ B very fast
2^nd step: B + C → D slow
3^rd step: D → 2E fast

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

Question 80

The combustion of ethylene proceeds by the reaction C₂H₄(g)+ 3O₂(g)→2CO₂(g)+ 2H₂O(g)
When the rate of disappearance of O₂ is 0.23 M s^-1,the rate of disappearance of C₂H₄ is ________ M s^-1.

A) 0.15
B) 0.077
C) 0.69
D) 0.35
E) 0.46