Deck 9: Reaction Kinetics

Question 1

For the following reaction H₂ (g) + I₂ (g)  2 HI (g), the initial rate of formation of hydrogen iodide was found to be 3.2 × 10^-3 mol dm^-3 s^-1. What is the initial rate of consumption of H₂?

A) 3.2 × 10^-3 mol dm^-3 s^-1.
B) 1.6 × 10^-3 mol dm^-3 s^-1.
C) 6.4 × 10^-3 mol dm^-3 s^-1.
D) Not possible to determine.

Answer 1

B

Question 2

For the following reaction: 2 N₂O₅ (g)  4 NO₂ (g) + O₂ (g) the initial rate of formation of O₂ was found to be 1.25 × 10^-4 mol dm^-3 s^-1. What is the initial rate of consumption of N₂O₅?

A) 2.50 × 10^-4 mol dm^-3 s^-1.
B) 1.25 × 10^-4 mol dm^-3 s^-1.
C) 3.75 × 10^-4 mol dm^-3 s^-1.
D) 5.00 × 10^-4 mol dm^-3 s^-1.

Answer 2

A

Question 3

For the following reaction: BrO₃^- (aq) + 5 Br^- (aq) + 6 H₃O⁺ (aq)  3 Br₂ (aq) + 9 H₂O (aq), the initial rate of formation of Br₂ was found to be 2.4 × 10^-3 mol dm^-3 s^-1. What is the initial rate of formation of H₂O?

A) 2.4 × 10^-3 mol dm^-3 s^-1.
B) 2.16 × 10^-2 mol dm^-3 s^-1
C) 4.8 × 10^-3 mol dm^-3 s^-1.
D) 7.2 × 10^-3 mol dm^-3 s^-1.

Answer 3

D

Question 4

For the following reaction: 2 NH₃ (g)  N₂ (g) + 3 H₂ (g), the rate of consumption of ammonia was measured as 2 mmol dm^-3 s^-1; what was the rate of formation of H₂?

A) 2 mmol dm^-3 s^-1.
B) 3 mmol dm^-3 s^-1.
C) 1 mmol dm^-3 s^-1.
D) 6 mmol dm^-3 s^-1.

Question 5

Which of the following are elementary reactions? Select all that apply.

A) H^ +Cl₂  HCl + Cl^
B) 2 NO (g) + O₂ (g)  2NO₂ (g)
C) BrO₃^- (aq) + 5Br^- (aq) + 6H₃O⁺ (aq)  3Br₂ (aq) + 9H₂O (aq)
D) (CH₃)₃C⁺ + H₂O  [(CH₃)₃COH₂]⁺

Question 6

For a general reaction aA + bB  products, the rate equation takes the form: rate of reaction = k[A]^a[B]^b. Match each of the following with its short description.
-overall order of the reaction = (a + b)

A) (a + b)
B) a
C) b
D) k

Question 7

For a general reaction aA + bB  products, the rate equation takes the form: rate of reaction = k[A]^a[B]^b. Match each of the following with its short description.
-order of the reaction with respect to A = a

A) (a + b)
B) a
C) b
D) k

Question 8

For a general reaction aA + bB  products, the rate equation takes the form: rate of reaction = k[A]^a[B]^b. Match each of the following with its short description.
-order of the reaction with respect to B = b

A) (a + b)
B) a
C) b
D) k

Question 9

For a general reaction aA + bB  products, the rate equation takes the form: rate of reaction = k[A]^a[B]^b. Match each of the following with its short description.
-rate constant = k

A) (a + b)
B) a
C) b
D) k

Question 10

For a general reaction 2A + 3B  products, the rate equation takes the form: rate of reaction = k [A]²[B]¹. Select all that apply.

A) The overall order of reaction = 2.
B) The order of reaction with respect to A = 2.
C) The order of the reaction with respect to B = 1.
D) The units of the rate constant k = s^-1.

Question 11

For the general reaction 2A + B  products, the rate equation takes the following form: rate of reaction = k[A]²[B]¹. What are the units of the rate constant, k?

A) s^-1.
B) dm³ mol^-1 s^-1.
C) mol dm^-3 s^-1.
D) dm⁶ mol^-2 s^-1.

Question 12

The rate of reaction in the following reaction: 2I (g) + Ar (g)  I₂ (g) + Ar (g) can be defined by which of the following expressions:

A) .
B) .
C) .
D) .

Question 13

The expression for the rate of reaction for the following elementary reaction NO + O₃ → NO₂ + O₂ is:

A) rate of reaction = k [NO] [O₃].
B) rate of reaction = k [NO] [O₃]³.
C) rate of reaction = k [NO₂] [O₂].
D) rate of reaction = .

Question 14

Which of the following expressions describes the rate of reaction for the elementary unimolecular process: O₃ → O₂ + O ?

A) Rate of reaction = k [O₂] [O].
B) Rate of reaction = k [O₃].
C) Rate of reaction = k [O₃]³ .
D) Rate of reaction = k [O₂]² [O].

Question 15

For the following elementary reaction: HF + NH₃ → F^- + NH₄⁺. The rate of consumption of the reactants and rate of formation of products is given by which set of expressions?

A)

B)
C)
D)

Question 16

For the following elementary reaction: 2Br^● → Br₂. The rate of consumption of the reactant and rate of formation of product is given by which set of expressions?

A)

B)
C)

D)

Question 17

For the following gas-phase bimolecular elementary reaction 2Cl^● → Cl₂, which rate equation, expressed in terms of a differential, shows the relationship between the rate of consumption of reactant and rate of reaction?

A)

B)

C)

D)

Question 18

2 N₂O₅ (g)  4 NO₂ (g) + O₂ (g) follows first order reaction kinetics, where the rate of reaction = k [N₂O₅]. The integrated form of the rate equation is:

A) [N₂O₅]_t = [N₂O₅]₀ - kt.
B) ln[N₂O₅]_t = ln[N₂O₅]₀ - kt .
C) 2[N₂O₅]_t = [N₂O₅]₀ - kt .
D) 2ln[N₂O₅]_t = ln[N₂O₅]₀ - kt .

Question 19

For the reaction 2 N₂O₅ (g)  4 NO₂ (g) + O₂ (g), the rate constant, k = 3.38 × 10^-5 s^-1. What is the overall reaction order?

A) Zero.
B) First.
C) Second.
D) Third.

Question 20

For a gas-phase reaction at 308 K, the rate constant k = 0.05 dm³ mol^-1 s^-1. What is the overall reaction order of the reaction?

A) Zero.
B) First.
C) Second.
D) Third.

Question 21

For a first order elementary reaction A  products, the rate of reaction = k[A]. Select all that apply.

A) .

B) .

C) ln[A]_t = ln[A]₀ - kt .
D) A plot of [A] versus time, t, will give a straight-line graph.

Question 22

A second order elementary reaction is characterised by a half life ( ) that gets shorter with the progress of the reaction.

Question 23

The first order gas-phase process: C₂H₆ → 2 CH₃ has a rate constant, k = 5.36 × 10^-4 s^-1 at 700 °C. If in a reaction vessel, the initial concentration of ethane was 0.05 mol dm^-3, what is its concentration after 250 s?

A) - 0.084 mol dm^-3
B) 0.034 mol dm^-3
C) 0.044 mol dm^-3
D) -3.13 mol dm^-3

Question 24

A first order reaction, with rate constant k = 3.25 × 10^-5 s^-1, at 200 °C, is followed experimentally over a period of 1 hour. The initial concentration of the reactant was 0.0280 mol dm^-3. What was the concentration of the reactant after one hour?

A) 0.0279 mol dm^-3
B) 0.0249 mol dm^-3
C) 0.0278 mol dm^-3
D) -0.089 mol dm^-3

Question 25

A researcher follows the progress of a reaction and tabulates the concentration of the reactant with respect to time of the reaction. How could the scientist prove that the reaction follows first order kinetics and find the rate constant, k? Select all that apply.

A) Impossible to do.
B) Plot a graph of [reactant] against time, and find a constant half-life ( ).
C) Plot a graph of ln[reactant] against time and get a linear plot.
D) Plot a graph of 1/[reactant] against time and get a linear plot.

Question 26

A researcher follows the progress of a reaction using spectroscopic methods. The half-life, ( ), is found to depend on the initial concentration of the reactant. This evidence suggests that the reaction is following first order kinetics.

Question 27

For a first order reaction, the half-life, = 237 s. What is the rate constant, k, of the reaction?

A) It is not possible to determine the rate constant.
B) 0.0029 s^-1.
C) 0.0084 s^-1.
D) 342 s.

Question 28

A first order rate constant, k = 3.75 × 10^-2 s^-1. What is the reaction's half-life, ?

A) 18.48 s.
B) 53.33 s.
C) 26.67 s.
D) 0.01875 s^-1.

Question 29

A reaction has a rate constant, k = 2.55 × 10^-3 mol^-1 dm³ s^-1. Select all that apply.

A) It is a second order reaction.
B) Double the concentration of the reactant, will quadruple the reaction rate.
C) Its half life = 272 s.
D) Its concentration will decay faster than a first order reaction with the same initial rate.

Question 30

Rate of reaction = [A]²[B]
What information does this give us? Select all that apply.

A) The overall reaction order is 2.
B) The reactant order with respect to reactant A is 2.
C) If the concentration of reactant B only is doubled, the rate of reaction quadruples.
D) The overall reaction order is 3.

Question 31

If the rate of reaction = [A]²[B], doubling the concentration of [A] will quadruple the rate of reaction. By doubling the concentration of [A] and the concentration of [B] the rate of reaction will increase 16 fold.

Question 32

Given the data below, which of the following statements is true?
Select all that apply.

A) The reaction is first order.
B) The reaction is second order.
C) The concentration after 700 seconds will be 0.95 × 10^-2 mol dm^-3.
D) The half-life is independent of temperature.

Question 33

The rate of reaction depends on the concentration of reactant A only. Calculate the order of the reaction from the data below.

A) Zero order.
B) First order.
C) Second order.
D) Third order.

Question 34

Match the following brief description with the term used to describe a reaction mechanism and its reaction steps.
-The step in a reaction mechanism that determines the rate of reaction

A) rate-determining step
B) bimolecular
C) steady state approximation
D) pre-equilibrium

Question 35

Match the following brief description with the term used to describe a reaction mechanism and its reaction steps.
-A reaction step that involves two molecules

A) rate-determining step
B) bimolecular
C) steady state approximation
D) pre-equilibrium

Question 36

Match the following brief description with the term used to describe a reaction mechanism and its reaction steps.
-The rate of change of concentration of a reactive species, in a sequence of reactions is approximately zero.

A) rate-determining step
B) bimolecular
C) steady state approximation
D) pre-equilibrium

Question 37

Match the following brief description with the term used to describe a reaction mechanism and its reaction steps.
-A reversible step preceding the rate-determining step

A) rate-determining step
B) bimolecular
C) steady state approximation
D) pre-equilibrium

Question 38

In the following reaction sequence the first step is reversible. and k₂ is small relative to k₁ and k_-1. Select all that apply.

A) where K_c is the equilibrium constant.
B) The rate-determining step is step two: .
C) .
D) .

Question 39

The Arrhenius equation describes how the rate of reaction of many chemical reactions varies with temperature . Match the symbol with its description.
-k

A) rate constant
B) activation energy
C) pre-exponential factor
D) ideal gas constant

Question 40

The Arrhenius equation describes how the rate of reaction of many chemical reactions varies with temperature . Match the symbol with its description.
-E_a

A) rate constant
B) activation energy
C) pre-exponential factor
D) ideal gas constant

Question 41

The Arrhenius equation describes how the rate of reaction of many chemical reactions varies with temperature . Match the symbol with its description.
-A

A) rate constant
B) activation energy
C) pre-exponential factor
D) ideal gas constant

Question 42

The Arrhenius equation describes how the rate of reaction of many chemical reactions varies with temperature . Match the symbol with its description.
-R

A) rate constant
B) activation energy
C) pre-exponential factor
D) ideal gas constant

Question 43

A plot of ln k against has a slope of - 3257 and an intercept of 25. What is the activation energy (E_a) (kJ mol^-1) of the reaction?

A) - 3257.
B) 27.
C) 25.
D) 392.

Question 44

A plot of ln (k / s^-1) against has a slope of - 2575 and an intercept of 31.5. What is the pre-exponential factor A (s^-1) of this first order reaction?

A) 31.5.
B) - 2575.
C) 21409.
D) 4.8 × 10¹³,

Question 45

A plot of ln k against has a slope of - 2752 and an intercept of 30. What is the activation energy (E_a) (kJ mol^-1) of the reaction?

A) 30.
B) 2752.
C) 23.
D) 331.

Question 46

The activation energy (E_a) of a first order reaction is 70 kJ mol^-1. The rate constant (k₁) at 25 °C is 2.25 × 10^-5 s^-1. What is the rate constant (k₂) (s^-1) at 70 °C?

A) 9.13 × 10^-4.
B) 2.39 × 10⁸⁹.
C) 2.26 × 10^-5.
D) 2.25 × 10^-5.

Question 47

The activation energy (E_a) of a first order reaction is 45 kJ mol^-1. The rate constant (k) at 75 °C is 5.75 × 10^-4 s^-1. What is the rate constant (s^-1) at 25 °C?

A) 4.24 × 10^-5.
B) 5.74 × 10^-4.
C) 1.19 × 10^-66.
D) 5.75 × 10^-4.

Question 48

At 30 °C and 85 °C the rate constants of a reaction are 3.75 × 10^-5 and 2.72 × 10^-3 s^-1 respectively. What is the activation energy E_a (kJ mol^-1)?

A) 1.65.
B) - 70.31.
C) 70.31.
D) 1.02.

Question 49

The activation energy E_a, of a reaction is - 5 kJ mol^-1; this suggests that temperature has no effect on the rate constant k, of the reaction.

Question 50

Which of the following statements are true with respect to the function of a catalyst in a reaction? Select all that apply.

A) It increases the rate of reaction.
B) It changes the amount of product formed.
C) It is chemically changed by the reaction.
D) It must be in the same physical state as the reaction in order to function.