elementary reaction involving two reactant entities

reaction that takes place in a single step, precisely as depicted in its chemical equation

entities produced in one step of a reaction mechanism and consumed in a subsequent step

number of reactant entities involved in an elementary reaction

rate-determining step

(also, rate-limiting step) slowest elementary reaction in a reaction mechanism; determines the rate of the overall reaction

stepwise sequence of elementary reactions by which a chemical change takes place

unimolecular reaction

elementary reaction involving a single reactant entity

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Chemistry 2e · 12.6 Reaction Mechanisms

Reaction Mechanisms: practice problems

4 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 68
In general, can we predict the effect of doubling the concentration of A on the rate of the overall reaction $A + B ⟶ C$ ? Can we predict the effect if the reaction is known to be an elementary reaction?
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Exercises 70
What is the rate law for the elementary termolecular reaction $A + 2 B ⟶ products?$ For $3 A ⟶ products?$
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Exercises 72
Write the rate law for each of the following elementary reactions:
(a) $O_{3} \to sunlight O_{2} + O$
(b) $O_{3} + Cl ⟶ O_{2} + ClO$
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Exercises 74
Experiments were conducted to study the rate of the reaction represented by this equation.2
$2NO (g) + 2 H_{2} (g) ⟶ N_{2} (g) + 2 H_{2} O (g)$
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Key terms · 8

bimolecular reaction: elementary reaction involving two reactant entities
elementary reaction: reaction that takes place in a single step, precisely as depicted in its chemical equation
intermediate: entities produced in one step of a reaction mechanism and consumed in a subsequent step
molecularity: number of reactant entities involved in an elementary reaction
rate-determining step: (also, rate-limiting step) slowest elementary reaction in a reaction mechanism; determines the rate of the overall reaction
reaction mechanism: stepwise sequence of elementary reactions by which a chemical change takes place
termolecular reaction: elementary reaction involving three reactant entities
unimolecular reaction: elementary reaction involving a single reactant entity

Learn 12.6 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 12.6 in the textbook · This section on openstax.org

Reaction Mechanisms: practice problems

4 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 68

In general, can we predict the effect of doubling the concentration of A on the rate of the overall reaction $A + B ⟶ C$ ? Can we predict the effect if the reaction is known to be an elementary reaction?

Exercises 70

What is the rate law for the elementary termolecular reaction $A + 2 B ⟶ products?$ For $3 A ⟶ products?$

Exercises 72

Write the rate law for each of the following elementary reactions:

(a) $O_{3} \to sunlight O_{2} + O$

(b) $O_{3} + Cl ⟶ O_{2} + ClO$

Exercises 74

Experiments were conducted to study the rate of the reaction represented by this equation.2

$2NO (g) + 2 H_{2} (g) ⟶ N_{2} (g) + 2 H_{2} O (g)$

Key terms · 8

bimolecular reaction: elementary reaction involving two reactant entities
elementary reaction: reaction that takes place in a single step, precisely as depicted in its chemical equation
intermediate: entities produced in one step of a reaction mechanism and consumed in a subsequent step
molecularity: number of reactant entities involved in an elementary reaction
rate-determining step: (also, rate-limiting step) slowest elementary reaction in a reaction mechanism; determines the rate of the overall reaction
reaction mechanism: stepwise sequence of elementary reactions by which a chemical change takes place
termolecular reaction: elementary reaction involving three reactant entities
unimolecular reaction: elementary reaction involving a single reactant entity

Learn 12.6 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 12.6 in the textbook · This section on openstax.org

Experiment	Initial Concentration [NO] (mol L⁻¹)	Initial Concentration, [H₂] (mol L⁻¹)	Initial Rate of Formation of N₂ (mol L⁻¹ min⁻¹)
1	0.0060	0.0010	1.8 $\times$ 10⁻⁴
2	0.0060	0.0020	3.6 $\times$ 10⁻⁴
3	0.0010	0.0060	0.30 $\times$ 10⁻⁴
4	0.0020	0.0060	1.2 $\times$ 10⁻⁴