Questions and Answers
What is meant by the term elementary reaction?
An elementary reaction is a single step reaction with a single transition state and no intermediates.
What is the difference between a unimolecular and a bimolecular elementary reaction?
A unimolecular reaction involves one species, while a bimolecular reaction involves two species.
What is a reaction mechanism?
A reaction mechanism is the step-by-step sequence of elementary reactions by which an overall chemical change occurs.
What is meant by the term molecularity?
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Why are termolecular elementary reactions so rare?
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What would the rate law be if the first step were rate determining for the reaction 2 NO(g) + Cl2(g) → 2 NOCl(g) with the proposed mechanism?
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Based on the observed rate law, what can we conclude about the proposed mechanism?
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Study Notes
Elementary Reactions
- An elementary reaction is a single-step reaction characterized by a single transition state, lacking intermediates.
- Unimolecular reactions involve one species transforming into products; an example includes O2 decomposing into O3.
- Bimolecular reactions involve two species reacting; examples include O2 and another reactant yielding products.
Reaction Mechanisms
- A reaction mechanism outlines the step-by-step sequence of elementary reactions leading to an overall chemical change.
- The molecularity of a reaction refers to the number of molecules involved in an elementary reaction step.
- Unimolecular: represented as A → products; Bimolecular: represented as A + B → products or 2A → products.
Termolecular Reactions
- Termolecular reactions involve three molecules colliding simultaneously, making them rare due to the low probability of correct orientation and collision.
- When they do occur, termolecular reactions are typically slow.
Rate Laws and Mechanisms
- The reaction 2 NO(g) + Cl2(g) → 2 NOCl(g) follows the rate law: rate = k[NO]²[Cl2].
- A proposed mechanism includes two steps: NO + Cl2 → NOCl2 and NOCl2 + NO → 2 NOCl.
- If the first step is rate-determining, the rate law would be based solely on its reactants.
- The observed rate law indicates that the proposed mechanism aligns with experimental data, confirming the participation of the specified reactants.
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Description
Test your understanding of elementary reactions in chemistry with this quiz. Explore the differences between unimolecular and bimolecular reactions and delve into the concept of reaction mechanisms. Perfect for students studying chemical kinetics.
