Textbook Question
Consider a hypothetical reaction between A, B, and C that is first order in A, zero order in B, and second order in C. (e) By what factor does the rate change when the concentrations of all three reactants are tripled?
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Ch.14 - Chemical Kinetics
Chapter 14, Problem 30b,c
Consider the following reaction:
2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g)
(b) If the rate constant for this reaction at 1000 K is 6.0 × 104 M-2 s-1, what is the reaction rate when [NO] = 0.035 M and [H2] = 0.015 M?
(c) What is the reaction rate at 1000 K when the concentration of NO is increased to 0.10 M, while the concentration of H2 is 0.010 M?
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Rate Law
The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. For a reaction of the form aA + bB → products, the rate can be described by the equation Rate = k[A]^m[B]^n, where k is the rate constant, and m and n are the orders of the reaction with respect to reactants A and B, respectively. Understanding the rate law is essential for calculating reaction rates based on varying concentrations.
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01:52
Rate Law Fundamentals
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, if the reaction is first order with respect to NO, doubling the concentration of NO will double the reaction rate. Identifying the order of each reactant is crucial for accurately determining the overall reaction rate.
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00:36Average Bond Order
Units of Rate Constant
The units of the rate constant (k) depend on the overall order of the reaction. For a second-order reaction, like the one given (2 NO + 2 H2 → N2 + 2 H2O), the units of k are M^-2 s^-1. This means that the rate of reaction is proportional to the product of the concentrations of the reactants raised to their respective orders. Understanding these units is vital for correctly applying the rate law to calculate reaction rates.
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Related Practice
Textbook Question
The decomposition reaction of N2O5 in carbon tetrachloride is 2 N2O5 → 4 NO2 + O2. The rate law is first order in N2O5. At 64°C the rate constant is 4.82 × 10-3 s-1. (a) Write the rate law for the reaction.
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Textbook Question
The decomposition reaction of N2O5 in carbon tetrachloride is 2 N2O5 → 4 NO2 + O2. The rate law is first order in N2O5. At 64°C the rate constant is 4.82 × 10-3 s-1. (c) What happens to the rate when the concentration of N2O5 is doubled to 0.0480 M? (d) What happens to the rate when the concentration of N2O5 is halved to 0.0120 M?
Textbook Question
Consider the following reaction: 2 NO1g2 + 2 H21g2¡N21g2 + 2 H2O1g2 (d) What is the reaction rate at 1000 K if [NO] is decreased to 0.010 M and 3H24 is increased to 0.030 M?
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Open Question
Consider the following reaction: CH3Br(aq) + OH-(aq) → CH3OH(aq) + Br-(aq). The rate law for this reaction is first order in CH3Br and first order in OH-. When [CH3Br] is 5.0 * 10^-3 M and [OH-] is 0.050 M, the reaction rate at 298 K is 0.0432 M/s. (c) What would happen to the rate if the concentration of OH- were tripled? (d) What would happen to the rate if the concentration of both reactants were tripled?
Textbook Question
The reaction between ethyl bromide (C2H5Br) and hydroxide ion in ethyl alcohol at 330 K, C2H5Br(alc) + OH-(alc) → C2H5OH(l) + Br-(alc), is first order each in ethyl bromide and hydroxide ion. When [C2H5Br] is 0.0477 M and [OH-] is 0.100 M, the rate of disappearance of ethyl bromide is 1.7×10-7 M/s. (a) What is the value of the rate constant?
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