Textbook Question
The reaction 2 NO(g) + O2(g) → 2 NO2 (g) is second order in NO and first order in O2. When [NO] = 0.040 M, and [O2] = 0.035 M, the observed rate of disappearance of NO is 9.3⨉10-5 M/s. (c) What are the units of the rate constant?
Ch.14 - Chemical Kinetics
Chapter 14, Problem 93b,c
Consider the following reaction between mercury(II) chloride and oxalate ion:
2 HgCl2(aq) + C2O42-(aq) → 2 Cl-(aq) + 2 CO2(g) + Hg2Cl2(s)
The initial rate of this reaction was determined for several concentrations of HgCl2 and C2O42-, and the following rate data were obtained for the rate of disappearance of C2O42-:
Experiment [HgCl2] (M) [C2O42-] (M) Rate (M/s)
1 0.164 0.15 3.2 × 10-5
2 0.164 0.45 2.9 × 10-4
3 0.082 0.45 1.4 × 10-4
4 0.246 0.15 4.8 × 10-5
(b) What is the value of the rate constant with proper units?
(c) What is the reaction rate when the initial concentration of HgCl2 is 0.100 M and that of C2O42- is 0.25 M if the temperature is the same as that used to obtain the data shown?
Verified step by step guidance1
Identify the rate law expression for the reaction. The general form is: \( \text{Rate} = k [\text{HgCl}_2]^m [\text{C}_2\text{O}_4^{2-}]^n \), where \( k \) is the rate constant, and \( m \) and \( n \) are the reaction orders with respect to \( \text{HgCl}_2 \) and \( \text{C}_2\text{O}_4^{2-} \), respectively.
Use the experimental data to determine the reaction orders \( m \) and \( n \). Compare experiments where only one concentration changes while the other remains constant to find \( m \) and \( n \).
Calculate the rate constant \( k \) using the rate law and data from one of the experiments once \( m \) and \( n \) are known.
Substitute the given concentrations \([\text{HgCl}_2] = 0.100 \text{ M}\) and \([\text{C}_2\text{O}_4^{2-}] = 0.25 \text{ M}\) into the rate law expression.
Calculate the reaction rate using the determined rate constant \( k \) and the substituted concentrations.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Rate of Reaction
The rate of a chemical reaction is a measure of how quickly reactants are converted into products. It can be expressed in terms of the change in concentration of a reactant or product over time. Understanding the rate is crucial for predicting how changes in concentration affect the speed of the reaction, which is essential for solving the given problem.
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02:03
Average Rate of Reaction
Rate Law
The rate law is an equation that relates the rate of a reaction to the concentration of its reactants, typically expressed as 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. Determining the rate law from experimental data allows us to predict the reaction rate under different concentrations, which is necessary for answering the question.
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01:52Rate Law Fundamentals
Concentration and Reaction Order
Concentration refers to the amount of a substance in a given volume, and it significantly influences the rate of a reaction. The reaction order indicates how the rate is affected by the concentration of each reactant. By analyzing the provided data, one can deduce the reaction order for HgCl2 and C2O4 2-, which is essential for calculating the reaction rate at new concentrations.
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02:44Zero-Order Reactions
Related Practice
Textbook Question
The reaction 2 NO(g) + O2(g) → 2 NO2 (g) is second order in NO and first order in O2. When [NO] = 0.040 M, and [O2] = 0.035 M, the observed rate of disappearance of NO is 9.3⨉10-5 M/s. (d) What would happen to the rate if the concentration of NO were increased by a factor of 1.8?
Textbook Question
The reaction 2 NO2 → 2 NO + O2 has the rate constant k = 0.63 M-1s-1. (a) Based on the units for k, is the reaction first or second order in NO2?
Textbook Question
The reaction 2 NO2 → 2 NO + O2 has the rate constant k = 0.63 M-1s-1.
(b) If the initial concentration of NO2 is 0.100 M, how would you determine how long it would take for the concentration to decrease to 0.025 M?