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Ch.14 - Chemical Kinetics
All textbooksMcMurry 8th EditionCh.14 - Chemical KineticsProblem 126
Chapter 14, Problem 126

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. (c) Does the reaction occur by a single-step mechanism? Explain.
Verified step by step guidance
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Step 1: Understand the reaction. The given reaction involves iodide ion (I-) and hypochlorite ion (OCl-) reacting to form chloride ion (Cl-) and hypoiodite ion (OI-).
Step 2: Consider the concept of a single-step mechanism. A single-step mechanism, also known as an elementary reaction, occurs in one step and involves a single transition state. The rate law for an elementary reaction can be directly written from the stoichiometry of the reaction.
Step 3: Analyze the concentration-time data. If the reaction follows a single-step mechanism, the rate law should match the stoichiometry of the balanced chemical equation. Check if the rate law derived from the experimental data matches the stoichiometric coefficients of the reactants.
Step 4: Compare the experimental rate law with the stoichiometric rate law. If the experimental rate law is different from what would be expected from the stoichiometry, the reaction likely does not occur in a single step.
Step 5: Conclude based on the comparison. If the rate law derived from the data does not match the stoichiometry, it suggests that the reaction involves multiple steps, indicating a complex mechanism rather than a single-step process.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reaction Mechanism

A reaction mechanism is a step-by-step description of the process by which reactants are converted into products. It outlines the individual elementary steps involved, including the formation of intermediates and the transition states. Understanding whether a reaction occurs in a single step or multiple steps is crucial for predicting reaction rates and the influence of concentration on the reaction.
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Rate Law

The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. It is determined experimentally and can indicate whether a reaction is elementary (single-step) or complex (multi-step). The form of the rate law can provide insights into the molecularity of the reaction and the number of reactant molecules involved in the rate-determining step.
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Elementary Reactions

Elementary reactions are single-step processes that occur in a single transition state, where reactants directly convert to products without intermediates. Each elementary reaction has a specific molecularity, which can be unimolecular, bimolecular, or termolecular, depending on the number of reactant molecules involved. Analyzing the concentration-time data can help determine if the observed reaction is elementary or involves multiple steps.
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Related Practice
Textbook Question

Consider the reaction H2(g) + I2(g) → 2 HI(g). The reaction of a fixed amount of H2 and I2 is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (c) The addition of a catalyst

Textbook Question
Concentration–time data for the conversion of A and B to D are listed in the following table.
(c) What is the rate law?

Textbook Question

Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion (OCl-). The products are chloride ion and hypoiodite ion (OI-).

(a) Write a balanced equation for the reaction.

Textbook Question

Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion (OCl-). The products are chloride ion and hypoiodite ion (OI-).

(b) Determine the rate law, and calculate the value of the rate constant.

Textbook Question

Consider the following concentration–time data for the reaction of iodide ion and hypochlorite ion (OCl-). The products are chloride ion and hypoiodite ion (OI-).

(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.)