Deck 11: Chemical Kinetics

Question 1

Consider the following reaction for production of ammonia via the Haber process: 3H ₂ + N ₂ → 2NH ₃ .
Which of the following expressions best illustrates the rate of reaction?

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.

Answer 1

rate = Δ [NH₃] \ 2 Δ t

Question 2

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

Answer 2

False

Question 3

A reaction mechanism is a collection of elementary steps.

Answer 3

True

Question 4

The rate of a reaction depends on the concentration of the reactants.

Question 5

Endothermic reactions do not require activation energy.

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

The _____ of a reaction can be obtained by measuring two concentrations of reactants at times separated by a finite difference.

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

Question 11

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

A)triple the rate of the reaction.
B)result in a fourfold increase in the rate of the reaction.
C)result in a ninefold increase in the rate of the reaction.
D)not affect the rate of the reaction.

Question 12

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

Question 13

For a zero-order reaction, a plot of a reactant concentration versus time is linear.

Question 14

O ₃ is the most stable allotrope of oxygen.

Question 15

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

Question 16

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

A)double the rate of the reaction.
B)result in a fourfold increase in the rate of the reaction.
C)result in an eightfold increase in the rate of the reaction.
D)not affect the rate of the reaction.

Question 17

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

A)double the rate of the reaction.
B)increase the rate of the reaction fourfold.
C)increase the rate of the reaction eightfold.
D)not affect the rate of the reaction.

Question 18

The formation of ozone in the stratosphere begins with:

A)a UV photon dissociating a diatomic oxygen molecule
B)a reaction between O₂and a CFC
C)the formation of a VOC radical
D)the formation of an O₄intermediate

Question 19

For a first order reaction, the plot of concentration of a reactant with respect to time is _____.

A)linear
B)exponential
C)parabolic
D)hyperbolic

Question 20

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

Question 21

A catalyst increases 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 these.

Question 22

The three-way catalytic converters found in automobile exhaust systems have a direct role in:

A)increasing the VOC emitted by the vehicle.
B)converting NO into O₂and N₂
C)the conversion of ozone to oxygen
D)creating large amounts of CFCs.

Question 23

Consider the following reaction:
A + 2B → C.
A kinetics study on this reaction yielded the following data: What is the order of the reaction with respect to ([A], [B])?

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

Question 24

Consider the following reaction: 2A + B → C.
A kinetics study on this reaction yielded the following data: What is the value of the rate constant?

A)3.20 mol L ^{− 1}s
B)19.8 mol L ⁻¹ s
C)0.508 mol L ⁻¹ s
D)4.60 mol L ⁻¹ s

Question 25

For a zero-order reaction, the plot of concentration with respect to time is _____.

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

Question 26

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

A)Unimolecular
B)Bimolecular
C)Termolecular
D)None of these

Question 27

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 28

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 29

The production of nitric oxide is governed by the following reaction: ​
4NH ₃ ( g )+ 5O ₂ ( g )→ 4NO( g )+ 6H ₂ O( g ).
​
If the rate at which NO is produced is 6.35 × 10 ^{− 2} mol L ^{− 1} s ^{− 1} , at what rate is O ₂ 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 30

Sulfur trioxide production follows the reaction:
2 SO₂( g )+ O₂( g )→ 2 SO₃( g )
If the rate at which SO₃is produced is 4.28 × 10 ^{− 4}mol L ^{− 1}s ^{− 1}, at what rate is SO₂consumed?

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 31

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

A)MgO
B)NO₂
C)CO₂
D)H₂O

Question 32

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

A)reactive intermediate.
B)inhibitor.
C)spectator ion.
D)catalyst.

Question 33

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

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

Question 34

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)85.8 mL\min
C)249 mL\min
D)429 mL\min

Question 35

The radioactive nuclide ¹⁴ C decays with a t _1\2 of 5730 years. An archaeologist is studying a woven mat using radiocarbon dating. If calculations related to the mat's original ¹⁴ C content reveal that there were 5.83 × 10 ²² atoms , how long ago was the mat woven? Modern spectroscopy was used to determine that 7.11 × 10 ²⁰ atoms of ¹⁴ C exist in the current sample.

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

Question 36

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 37

Burning of Mg metal results in the formation of MgO. Which of the following 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 these

Question 38

Consider the following reaction: 2A + B → C.
A kinetics study on this reaction yielded the following data: What is the order of the reaction with respect to ([A], [B])?

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

Question 39

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

A)increasing the activation energy of the reaction.
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 40

Consider the production of oxygen from ozone. The mechanism involves two elementary steps:
O ₃ + Cl → ClO + O ₂ and ClO + O ₃ → Cl + 2O ₂ .
Which of the following species is a reactive intermediate?

A)O₃
B)ClO
C)Cl
D)both ClO and Cl

Question 41

The U.S. Environmental Protection Agency (EPA)has identified Pb as one of the criteria pollutants.

Question 42

The radioactive nuclide ²³⁵ U decays with a t _1\2 of 703.8 million years. Calculations reveal that there were 10.53 × 10 ²³ atoms of ²³⁵ U present in an initial sample. If modern spectroscopy shows that 3.25 × 10 ²¹ atoms of ²³⁵ U now exist in the sample, how long ago did the decay begin?

A)5.9 × 10 ⁹ years ago
B)4.1 × 10 ⁹ years ago
C)9.8 × 10 ⁸ years ago
D)7.6 × 10 ⁸ years ago

Question 43

In zero-order reactions, the rate of reaction does not change as the reactants are consumed.

Question 44

The order of a chemical reaction is usually an integer greater than 2.

Question 45

Which of the following terms best describes the following elementary step: A + 2B + 3C → D?

A)Unimolecular
B)Bimolecular
C)Termolecular
D)Quadmolecular