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Ch.14 - Chemical Kinetics
Chapter 14, Problem 40a

A reaction in which A, B, and C react to form products is zero order in A, one-half order in B, and second order in C. a. Write a rate law for the reaction.

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Identify the general form of the rate law: \( \text{Rate} = k[A]^m[B]^n[C]^p \).
Determine the order of reaction with respect to each reactant: \( m = 0 \) for A, \( n = \frac{1}{2} \) for B, and \( p = 2 \) for C.
Substitute the orders into the rate law expression: \( \text{Rate} = k[A]^0[B]^{1/2}[C]^2 \).
Simplify the expression by noting that any concentration raised to the power of zero is 1: \( \text{Rate} = k[B]^{1/2}[C]^2 \).
The final rate law for the reaction is \( \text{Rate} = k[B]^{1/2}[C]^2 \).

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Key Concepts

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

Order of Reaction

The order of a reaction refers to the power to which the concentration of a reactant is raised in the rate law. It indicates how the rate of reaction is affected by the concentration of that reactant. For example, a zero-order reaction means the rate is independent of the concentration of that reactant, while a first-order reaction means the rate is directly proportional to its concentration.
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Rate Law

The rate law is an equation that relates the rate of a chemical reaction to the concentrations of the reactants, each raised to a power corresponding to its order in the reaction. It is typically expressed in the form: Rate = k[A]^m[B]^n[C]^p, where k is the rate constant, and m, n, and p are the orders of the reactants A, B, and C, respectively. Understanding the rate law is crucial for predicting how changes in concentration affect the reaction rate.
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Rate Constant (k)

The rate constant, denoted as k, is a proportionality factor in the rate law that is specific to a given reaction at a specific temperature. It reflects the intrinsic speed of the reaction and is influenced by factors such as temperature and the presence of catalysts. The value of k can vary with the order of the reaction and is essential for calculating the rate of the reaction under different conditions.
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