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15. Chemical Kinetics

Reaction Mechanism

15. Chemical Kinetics

Reaction Mechanism

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Reaction Mechanism Concept 1

Reaction Mechanism Concept 1

Reaction Mechanism Example 1

Reaction Mechanism Example 1

Reaction Mechanism Concept 2

Reaction Mechanism Concept 2

Reaction Mechanism Example 2

Reaction Mechanism Example 2

Reaction Mechanism Concept 3

Reaction Mechanism Concept 3

Reaction Mechanism Example 3

Reaction Mechanism Example 3

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14.3 Reaction Mechanisms, Catalysts, and Reaction Coordinate Diagrams | General Chemistry

14.3 Reaction Mechanisms, Catalysts, and Reaction Coordinate Diagrams | General Chemistry

Writing Rate Laws of Reaction Mechanisms Using The Rate Determining Step - Chemical Kinetics

Writing Rate Laws of Reaction Mechanisms Using The Rate Determining Step - Chemical Kinetics

The Organic Chemistry Tutor

Reaction Mechanisms

Reaction Mechanisms

00π productions

Energy Diagrams, Catalysts, and Reaction Mechanisms

Energy Diagrams, Catalysts, and Reaction Mechanisms

Professor Dave Explains

Kinetics: Chemistry's Demolition Derby - Crash Course Chemistry #32

Kinetics: Chemistry's Demolition Derby - Crash Course Chemistry #32

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Practice this topic

Multiple Choice

Consider the following elementary steps:

NO₂ (g) + NO₂ (g) → NO₃ (g) + NO (g) [SLOW]

NO (g) + CO₃ (g) → N (g) + CO₄ (g) [FAST]

What is the rate law of the reaction mechanism?

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Multiple Choice

The following reaction of 2 Br₂ (g) + 2 NO (g) → N₂ (g) + 2 Br₂O (g) has the following rate law:Rate = k [Br₂][NO]². The proposed mechanism for the reaction is:

Br₂ (g) + NO₂ (g) → N (g) + Br₂O (g) [SLOW]
N (g) + NO (g) → N₂ (g) + O (g) [FAST]
O (g) + Br₂ (g) → Br₂O (g) [FAST]

Which of the following statements is/are false?

a) The rate determining step is bimolecular.
b) There are three elementary steps in the reaction mechanism.
c) The mechanism possesses a catalyst.
d) O is the only reaction intermediate in this reaction mechanism.
e) This is not a valid mechanism for the reaction.

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Textbook Question

Consider the diagram that follows, which represents two steps in an overall reaction. The red spheres are oxygen, the blue ones nitrogen, and the green ones fluorine. (d) Write the rate law for the overall reaction if the first step is the slow, rate-determining step. [Section 14.6]

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Textbook Question

To answer questions 13–15, refer to the mechanism: H2O21aq2 + I-1aq2¡OH-1aq2 + HOI1aq2 Slower, rate-determining HOI1aq2 + I-1aq2¡OH-1aq2 + I21aq2 Faster 2 OH-1aq2 + 2 H3O+1aq2¡4 H2O1l2 Faster Identify the catalyst and intermediate(s) in the mechanism. (LO 14.12, 14.16) (a) Catalyst = I-, intermediates = OH-, HOI (b) Catalyst = H3O+, intermediate = HOI (c) No catalyst, intermediate = I2 (d) No catalyst, intermediates = OH-, HOI

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Textbook Question

(b) Write the balanced reaction that corresponds to the data in the graph.

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Textbook Question

What is the molecularity of each of the following elementary reactions? (a)

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Textbook Question

Draw a plausible transition state for the bimolecular reaction of nitric oxide with ozone. Use dashed lines to indicate the atoms that are weakly linked together in the transition state. NO(g) + O3(g) NO2(g) + O2(g)

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Textbook Question

(b) What is the difference between a unimolecular and a bimolecular elementary reaction?

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Textbook Question

What is the molecularity of each of the following elementary reactions? Write the rate law for each. (c) NO1g2 + Cl21g2¡NOCl21g2

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Textbook Question

What is the molecularity of each of the following elementary reactions? Write the rate law for each. (b) OCl - 1aq2 + H2O1l2¡HOCl1aq2 + OH- 1aq2

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Textbook Question

What is the molecularity of each of the following elementary reactions? Write the rate law for each. (a) Cl21g2¡2 Cl1g2

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Textbook Question

What is the molecularity of each of the following elementary reactions? Write the rate law for each. (b) H2C ¬ CH2CH21g2¡CH2'CH¬CH31g2

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Textbook Question

What is the molecularity of each of the following elementary reactions? Write the rate law for each. (a) 2 NO1g2¡N2O21g2

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Textbook Question

Consider the following energy profile.

(a) How many elementary reactions are in the reaction mechanism?

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Textbook Question

The decomposition of hydrogen peroxide is catalyzed by iodide ion. The catalyzed reaction is thought to proceed by a two-step mechanism: H2O21aq2 + I - 1aq2¡H2O1l2 + IO- 1aq2 1slow2 IO- 1aq2 + H2O21aq2¡H2O1l2 + O21g2 + I - 1aq2 1fast2 (c) Assuming that the first step of the mechanism is rate determining, predict the rate law for the overall process.

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Textbook Question

The decomposition of hydrogen peroxide is catalyzed by iodide ion. The catalyzed reaction is thought to proceed by a two-step mechanism: H2O21aq2 + I - 1aq2¡H2O1l2 + IO- 1aq2 1slow2 IO- 1aq2 + H2O21aq2¡H2O1l2 + O21g2 + I - 1aq2 1fast2 (a) Write the chemical equation for the overall process.

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Textbook Question

The decomposition of hydrogen peroxide is catalyzed by iodide ion. The catalyzed reaction is thought to proceed by a two-step mechanism: H2O21aq2 + I - 1aq2¡H2O1l2 + IO- 1aq2 1slow2 IO- 1aq2 + H2O21aq2¡H2O1l2 + O21g2 + I - 1aq2 1fast2 (b) Identify the intermediate, if any, in the mechanism.

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Textbook Question

The reaction 2 NO1g2 + Cl21g2¡2 NOCl1g2 was performed and the following data were obtained under conditions of constant 3Cl24:

(a) Is the following mechanism consistent with the data? NO1g2 + Cl21g2ΔNOCl21g2 1fast2 NOCl21g2 + NO1g2¡2 NOCl1g2 1slow2

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Textbook Question

You have studied the gas-phase oxidation of HBr by O2: 4 HBr1g2 + O21g2¡2 H2O1g2 + 2 Br21g2 You find the reaction to be first order with respect to HBr and first order with respect to O2. You propose the following mechanism: HBr1g2 + O21g2¡ HOOBr1g2 HOOBr1g2 + HBr1g2¡2 HOBr1g2 HOBr1g2 + HBr1g2¡ H2O1g2 + Br21g2 (a) Confirm that the elementary reactions add to give the overall reaction.

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Textbook Question

You have studied the gas-phase oxidation of HBr by O2: 4 HBr1g2 + O21g2¡2 H2O1g2 + 2 Br21g2 You find the reaction to be first order with respect to HBr and first order with respect to O2. You propose the following mechanism: HBr1g2 + O21g2¡ HOOBr1g2 HOOBr1g2 + HBr1g2¡2 HOBr1g2 HOBr1g2 + HBr1g2¡ H2O1g2 + Br21g2 (b) Based on the experimentally determined rate law, which step is rate determining?

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Textbook Question

Consider this overall reaction, which is experimentally observed to be second order in AB and zero order in C: AB + C¡A + BC Is the following mechanism valid for this reaction? AB + AB ¡k1AB2 + A Slow AB2 + C ¡k2AB + BC Fast

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Textbook Question

Consider this three-step mechanism for a reaction: Cl2( g) Δk1k22 Cl( g) Fast Cl( g) + CHCl3( g) ¡k3 HCl( g) + CCl3( g) Slow Cl( g) + CCl3( g) ¡k4 CCl4( g) Fast a. What is the overall reaction?

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Textbook Question

Consider this three-step mechanism for a reaction:

Cl₂ (g) k₁⇌k₂ 2 Cl (g) Fast

Cl (g) + CHCl₃ (g) →k₃ HCl (g) + CCl₃ (g) Slow

Cl (g) + CCl₃ (g) →k₄ CCl₄ (g) Fast

c. What is the predicted rate law?

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Textbook Question

Consider this two-step mechanism for a reaction: NO2( g) + Cl2( g) ¡k1ClNO2( g) + Cl( g) Slow NO2( g) + Cl( g) ¡k2ClNO2( g) Fast b. Identify the intermediates in the mechanism.

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Textbook Question

The addition of NO accelerates the decomposition of N2O, possibly by the following mechanism: NO1g2 + N2O1g2¡N21g2 + NO21g2 2 NO21g2¡2 NO1g2 + O21g2 (b) Is NO serving as a catalyst or an intermediate in this reaction?

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Textbook Question

Consider this energy diagram:

a. How many elementary steps are involved in this reaction?

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Textbook Question

Consider the reaction in which HCl adds across the double bond of ethene: HCl + H2C'CH2¡H3C¬CH2Cl The following mechanism, with the accompanying energy diagram, has been suggested for this reaction: Step 1 HCl + H2C'CH2¡H3C'CH2+ + Cl - Step 2 H3C'CH2+ + Cl - ¡H3C¬CH2Cl

b. What is the expected order of the reaction based on the proposed mechanism?

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Textbook Question

What is the relationship between the coefficients in a balanced chemical equation for an overall reaction and the exponents in the rate law?

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Textbook Question

What distinguishes the rate-determining step from the other steps in a reaction mechanism? How does the ratedetermining step affect the observed rate law?

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Textbook Question

Consider the gas-phase reaction: H2( g) + I2( g)¡2 HI( g) The reaction was experimentally determined to be first order in H2 and first order in I2. Consider the proposed mechanisms. Proposed mechanism I: H2( g) + I2( g)¡2 HI( g) Single step Proposed mechanism II: I2(g) Δk1k-12 I(g) Fast H2( g) + 2 I( g) ¡k22 HI( g) Slow b. What kind of experimental evidence might lead you to favor mechanism II over mechanism I?

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Textbook Question

Consider the gas-phase reaction: H2( g) + I2( g)¡2 HI( g) The reaction was experimentally determined to be first order in H2 and first order in I2. Consider the proposed mechanisms. Proposed mechanism I: H2( g) + I2( g)¡2 HI( g) Single step Proposed mechanism II: I2(g) Δk1k-12 I(g) Fast H2( g) + 2 I( g) ¡k22 HI( g) Slow a. Show that both of the proposed mechanisms are valid.

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Textbook Question

Consider the following mechanism for the reaction of hydrogen and iodine monochloride: Step 1. H21g2 + ICl1g2S HI1g2 + HCl1g2 Step 2. HI1g2 + ICl1g2S I21g2 + HCl1g2 (b) Identify any reaction intermediates.

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Textbook Question

Consider the reaction: 2 NH3(aq) + OCl - (aq)¡N2H4(aq) + H2O(l ) + Cl - (aq) This three-step mechanism is proposed: NH3(aq) + OCl - (aq) Δk1k2NH2Cl(aq) + OH- (aq) Fast NH2Cl(aq) + NH3(aq) ¡k3N2H5+ (aq) + Cl - (aq) Slow N2H5+ (aq) + OH- (aq) ¡k4N2H4(aq) + H2O(l ) Fast a. Show that the mechanism sums to the overall reaction.

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Textbook Question

The following mechanism has been proposed for the reaction of NO with H2 to form N2O and H2O: NO1g2 + NO1g2¡N2O21g2 N2O21g2 + H21g2¡N2O1g2 + H2O1g2 (d) The observed rate law is rate = k3NO423H24. If the proposed mechanism is correct, what can we conclude about the relative speeds of the first and second reactions?

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Textbook Question

Ozone in the upper atmosphere can be destroyed by the following two-step mechanism: Cl1g2 + O31g2¡ClO1g2 + O21g2 ClO1g2 + O1g2¡Cl1g2 + O21g2 (b) What is the catalyst in the reaction?

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Textbook Question

The gas-phase decomposition of ozone is thought to occur by the following two-step mechanism. Step 1: O31g2ΔO21g2 + O1g2 (fast) Step 2: O1g2 + O31g2¡2 O21g2 (slow) (d) If instead the reaction occurred in a single step, would the rate law change? If so, what would it be?

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Textbook Question

The gas-phase decomposition of ozone is thought to occur by the following two-step mechanism. Step 1: O31g2ΔO21g2 + O1g2 (fast) (b) Derive the rate law that is consistent with this mechanism. (Hint: The product appears in the rate law.)

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Textbook Question

The thermal decomposition of nitryl chloride, NO2Cl, is believed to occur by the following mechanism: NO2Cl1g2 ¡ k1 NO21g2 + Cl1g2 Cl1g2 + NO2Cl1g2 ¡ k2 NO21g2 + Cl21g2 (c) What rate law is predicted by this mechanism if the first step is rate-determining?

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Textbook Question

The following mechanism has been proposed for the gasphase reaction of chloroform 1CHCl32 and chlorine: Step 1: Cl21g2 Δ k1 k - 1 2 Cl1g2 1fast2 Step 2: Cl1g2 + CHCl31g2 ¡k2 HCl1g2 + CCl31g2 1slow2 Step 3: Cl1g2 + CCl31g2 ¡k3 CCl4 1fast2 (a) What is the overall reaction?

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Textbook Question

In a hydrocarbon solution, the gold compound 1CH323AuPH3 decomposes into ethane 1C2H62 and a different gold compound, 1CH32AuPH3. The following mechanism has been proposed for the decomposition of 1CH323AuPH3: Step 1: 1CH323 AuPH3 Δ k1 k -1 1CH323Au + PH3 1fast2 Step 2: 1CH323 Au ¡k2 C2H6 + 1CH32Au 1slow2 Step 3: 1CH32Au + PH3 ¡k3 1CH32AuPH3 1fast2 (c) What is the molecularity of each of the elementary steps?

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Textbook Question

In a hydrocarbon solution, the gold compound 1CH323AuPH3 decomposes into ethane 1C2H62 and a different gold compound, 1CH32AuPH3. The following mechanism has been proposed for the decomposition of 1CH323AuPH3: Step 1: 1CH323 AuPH3 Δ k1 k -1 1CH323Au + PH3 1fast2 Step 2: 1CH323 Au ¡k2 C2H6 + 1CH32Au 1slow2 Step 3: 1CH32Au + PH3 ¡k3 1CH32AuPH3 1fast2 (e) What is the rate law predicted by this mechanism?

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Textbook Question

A proposed mechanism for the oxidation of nitric oxide to nitrogen dioxide was described in Problem 14.29. Another possible mechanism for this reaction is 2 NO1g2 k1 k-1 N2O21g2 Faster, reversible N2O21g2 + O21g2 ¡ k2 2NO21g2 Slower, rate-determining (b) Show that this mechanism is consistent with the experimental rate law, Rate = k3NO423O24.

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Textbook Question

A proposed mechanism for the oxidation of nitric oxide to nitrogen dioxide was described in Problem 14.29. Another possible mechanism for this reaction is 2 NO1g2 k1 k-1 N2O21g2 Faster, reversible N2O21g2 + O21g2 ¡ k2 2NO21g2 Slower, rate-determining (a) Write a balanced equation for the overall reaction.

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Textbook Question

A proposed mechanism for the oxidation of nitric oxide to nitrogen dioxide was described in Problem 14.29. Another possible mechanism for this reaction is 2 NO1g2 k1 k-1 N2O21g2 Faster, reversible N2O21g2 + O21g2 ¡ k2 2NO21g2 Slower, rate-determining (c) Relate the rate constant k to the rate constants for the elementary reactions.

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Textbook Question

Enzymes are often described as following the two-step mechanism: E + S Δ ES 1fast2 ES ¡ E + P 1slow2 where E = enzyme, S = substrate, ES = enzyme9substrate complex, and P = product. (b) Molecules that can bind to the active site of an enzyme but are not converted into product are called enzyme inhibitors. Write an additional elementary step to add into the preceding mechanism to account for the reaction of E with I, an inhibitor.

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Textbook Question

Consider the following mechanism for the decomposition of nitramide 1NH2NO22 in aqueous solution: NH2NO21aq2 + OH-1aq2S NHNO2 -1aq2 + H2O1l2 NHNO2 -1aq2S N2O1g2 + OH-1aq2 (c) How will the rate of the overall reaction be affected if HCl is added to the solution?

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Textbook Question

In Problem 14.113, you wrote a mechanism for the nitric oxide– facilitated decomposition of ozone. Does your mechanism involve a catalyst or a reaction intermediate? Explain.

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Textbook Question

The rate of the reaction A + B2 S AB + B is directly proportional to the concentration of B2, independent of the concentration of A, and directly proportional to the concentration of a substance C. (c) What is the role of C in this reaction? Why doesn't C appear in the chemical equation for the overall reaction?

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Textbook Question

Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion 1OCl-2. The products are chloride ion and hypoiodite ion 1OI-2. (d) Propose a mechanism that is consistent with the rate law, and express the rate constant in terms of the rate constants for the elementary steps in your mechanism. (Hint: Transfer of an H+ ion between H2O and OCl- is a rapid reversible reaction.)

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