Deck 11: Chemical Kinetics

Question 1

A reaction mechanism is a collection of elementary steps.

Answer 1

True

Question 2

According to the differential rate law: rate = k[X]^m[Y]ⁿ. If m = 2 and n = 1, the overall reaction order is:

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

Answer 2

3

Question 3

For a 1st order reaction, a plot of concentration with respect to time produces a plot that is:

A) linear
B) non-linear
C) parabolic
D) linear; m = 0

Answer 3

non-linear

Question 4

If a reaction is first order with respect to [A], doubling the concentration of [A] will result in:

A) a doubling of the rate
B) a four-fold increase in rate
C) an eight-fold increase in rate
D) no change in the rate of reaction

Question 5

The instantaneous rate of a reaction is determined using the slope of a line tangent to the curve of the change of concentration versus time.

Question 6

For a first-order reaction, t_1/2 = ln 2/ k

Question 7

The production of ozone begins with:

A) a UV photon dissociating a diatomic oxygen molecule
B) a reaction between O₂ and a CFC
C) the formation of a VOC radical
D) the formation of an O₄ intermediate

Question 8

A termolecular step in a reaction mechanism is a step that involves two molecules.

Question 9

The rate of a reaction may be expressed as the disappearance of reactants with respect to time.

Question 10

O₃, not O₂, is the thermodynamically favored allotrope of oxygen for the conditions found at the Earth's surface.

Question 11

When two concentrations are measured at times separated by a finite difference, the ____ may be calculated:

A) entropic rate
B) induced rate
C) average rate
D) instantaneous rate

Question 12

Stirring a reaction increases the rate of the reaction by raising the energy of activation.

Question 13

For a first-order reaction, a plot of concentration vs time provides a line with a slope equal to − k.

Question 14

If a reaction is 1st order with respect to [A] and 2nd order with respect to [B], doubling the concentration of reactant [B] will result in a four-fold increase in the rate of reaction.

Question 15

If a reaction is zero order with respect to [B], tripling the concentration of [B] will result in:

A) a tripling of the rate
B) a four-fold increase in rate
C) a nine-fold increase in rate
D) no change in the rate of reaction

Question 16

Endothermic reactions do not require activation energy.

Question 17

A plot of a reactant concentration vs. time is linear for a zeroth order reaction.

Question 18

If a reaction is second order with respect to [A], doubling the concentration of [A] will result in:

A) a doubling of the rate
B) a four-fold increase in rate
C) an eight-fold increase in rate
D) no change in the rate of reaction

Question 19

The rate constant "k" will vary with changes in concentration of 1st order reactants.

Question 20

Which statement best describes the rate of reaction for the production of ammonia via the Haber reaction ( 3 H₂ + N₂ → 2 NH₃)

A) rate = 2 Δ [NH₃] / Δ t
B) rate = Δ [NH₃] / 2 Δ t
C) rate = 2 Δ [NH₃] / 2 Δ t
D) There is too little information to assess the change.

Question 21

Consider the reaction: 2A + B → C,
And a kinetics study on this reaction yielded:

What order is the reaction with respect to ([A], [B])?

A) 1, 2
B) 2, 1
C) 2, 0
D) 0, 2

Question 22

The decomposition of hydrogen peroxide (H₂O₂) into O₂( g ) and liquid H₂O produced the following data:
What is the average rate in mL/min for the third ten-minute period of the reaction?

A) 6.72 mL/min
B) 10.1 mL/min
C) 7.98 mL/min
D) 15.7 mL/min

Question 23

A catalyst elevates the rate of a reaction by:

A) lowering the activation energy
B) decreasing the effectiveness of molecular collisions
C) increasing the number of molecular collisions
D) none of the above

Question 24

The synthesis of ammonia from hydrogen and nitrogen produced the following kinetic data:
What is the average rate in mL/min for the second five-minute period of the reaction?

A) 167 mL/min
B) 85.3 mL/min
C) 249 mL/min
D) 429 mL/min

Question 25

Consider the reaction: 2A + B → C, What is the value of the rate constant?

A) 3.20 mol L ^{− 1}s
B) 19.8 mol L ^{− 1}s
C) 0.530 mol L ^{− 1}s
D) 4.60 mol L ^{− 1}s

Question 26

Consider the reaction: A + 2B → C,
And a kinetics study on this reaction yielded:

What order is the reaction with respect to ([A], [B])?

A) 1, 2
B) 2, 2
C) 2, 1
D) 0, 2

Question 27

During the formation of MgO from the burning of Mg metal, what steps will result in an increase in the rate of reaction?

A) increasing the metal surface area by milling
B) selecting tarnished pieces of magnesium for the experiment
C) increasing the amount of metal by selecting a larger cube of magnesium
D) none of the above.

Question 28

Raising the temperature of a reaction elevates the rate of reaction by:

A) increasing the energy of activation
B) creating more molecules in the reaction.
C) increasing the number of molecules moving at a speed sufficiently high enough to produce a reactive collision.
D) decreasing the entropy of the system.

Question 29

The synthesis of ammonia from hydrogen and nitrogen produced the following kinetic data:

What is the average rate in mL/min for the first five minutes of the reaction?

A) 167 mL/min
B) 85.3 mL/min
C) 249 mL/min
D) 429 mL/min

Question 30

Consider the production of oxygen from ozone. The mechanism includes two elementary steps:
O₃ + Cl → ClO + O₂ ClO + O₃ → Cl + 2O₂
Which species is a reactive intermediate?

A) O₃
B) ClO
C) Cl
D) both ClO and Cl

Question 31

The production of nitric oxide is governed by the reaction:
4 NH₃( g ) + 5 O₂( g ) → 4 NO( g ) + 6 H₂O( g )
If the rate at which NO is produced is 6.35 × 10 ⁻² mol L ^{− 1}s ^{− 1}, at what rate is O₂ consumed?

A) 8.29 × 10 ^{− 3} mol L ^{− 1}s ^{− 1}
B) 1.59 × 10 ^{− 2} mol L ^{− 1}s ^{− 1}
C) 6.35 × 10 ⁻² mol L ^{− 1}s ^{− 1}
D) 7.94 × 10 ⁻² mol L ^{− 1}s ^{− 1}

Question 32

The catalytic converter on an automobile has a direct role in:

A) increasing the VOC emitted by the vehicle.
B) converting NO into O₂ and N₂
C) the conversion of ozone to oxygen
D) creating large amounts of PtN

Question 33

Lowering the activation energy of a reaction will increase the rate of reaction by:

A) removing potential energy from the reactants.
B) spontaneously increasing the amount of reactants.
C) packing the created products in a favored arrangement.
D) providing a new reaction mechanism.

Question 34

For a zero order reaction, a plot of concentration with respect to time produces a plot that is:

A) linear; m = − k
B) non-linear
C) parabolic
D) linear; m = 0

Question 35

A chemical species that is not consumed by the reaction and increases the rate of the reaction is referred to as a(n):

A) reactive intermediate
B) entropic entity
C) spectator ion
D) catalyst

Question 36

The radioactive nuclide ¹⁴C decays with a t_1/2 of 5730 yrs. An archaeologist is studying a woven mat using radiocarbon dating. If calculations related to the mat's original ¹⁴C content reveal that there was 5.83 × 10²² atoms of ¹⁴C present in the plant used to weave the mat, how long ago was the mat woven if modern spectroscopy was used to determine that 7.11 × 10²⁰ atoms of ¹⁴C now exist in the sample?

A) 8.3 × 10⁴ yrs
B) 4.1 × 10² yrs
C) 3.6 × 10⁴ yrs
D) 5.0 × 10⁶ yrs

Question 37

Sulfur trioxide production follows the reaction:
2 SO₂( g ) + O₂( g ) → 2 SO₃( g )
If the rate at which SO₃ is produced is 4.28 × 10 ^{− 4} mol L ^{− 1}s ^{− 1}, at what rate is SO₂ consumed?

A) 4.28 × 10 ^{− 4} mol L ^{− 1}s ^{− 1}
B) 1.08 × 10 ^{− 3} mol L ^{− 1}s ^{− 1}
C) 1.07 × 10 ^{− 4} mol L ^{− 1}s ^{− 1}
D) 2.14 × 10 ^{− 4} mol L ^{− 1}s ^{− 1}

Question 38

Consider the elementary step: A + B → C. What type of elementary step is this?

A) unimolecular
B) bimolecular
C) termolecular
D) none of the above

Question 39

If the decomposition of reactant A follows first-order kinetics, what concentration of A remains if:
[A]₀ = 0.273 M, k = 1.53 × 10 ^{− 2} minutes ^{− 1}, and the elapsed time = 1.61 hr?

A) 0.009 M
B) 0.0623 M
C) 0.109 M
D) 0.273 M

Question 40

Which of the following internal combustion engine products plays the largest role in the production of smog?

A) heat
B) NO₂
C) CO₂
D) H₂O