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What is the rate of change calculated from the two given points: (1200, 0.0040) and (3400, 0.0066)?
What is the rate of change calculated from the two given points: (1200, 0.0040) and (3400, 0.0066)?
Which of the following factors typically leads to an increase in the rate of a chemical reaction based on the content?
Which of the following factors typically leads to an increase in the rate of a chemical reaction based on the content?
What is the primary role of a catalyst in a chemical reaction?
What is the primary role of a catalyst in a chemical reaction?
What type of rate law expresses how the reaction rate changes with concentration for each reactant?
What type of rate law expresses how the reaction rate changes with concentration for each reactant?
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What is one method mentioned in the text for determining the differential rate law experimentally?
What is one method mentioned in the text for determining the differential rate law experimentally?
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Which factor is described as often increasing the reaction rate when its value is increased?
Which factor is described as often increasing the reaction rate when its value is increased?
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Which of the following describes how the integrated rate law is obtained?
Which of the following describes how the integrated rate law is obtained?
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What does the differential rate law primarily relate to?
What does the differential rate law primarily relate to?
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Under what condition can the reverse reaction be considered negligible when writing the rate law?
Under what condition can the reverse reaction be considered negligible when writing the rate law?
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Given the reaction $aA + bB \rightarrow cC + dD$, how is the rate of the reaction expressed in terms of the change in concentration of the reactants and products over time?
Given the reaction $aA + bB \rightarrow cC + dD$, how is the rate of the reaction expressed in terms of the change in concentration of the reactants and products over time?
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If the rate of consumption of N$_2$O$_5$ is 5.0 x 10$^{-5}$ M/s, what is the rate of formation of O$_2$ in the reaction 2N$_2$O$_5$ -> 4NO$_2$ + O$_2$?
If the rate of consumption of N$_2$O$_5$ is 5.0 x 10$^{-5}$ M/s, what is the rate of formation of O$_2$ in the reaction 2N$_2$O$_5$ -> 4NO$_2$ + O$_2$?
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What is the relationship between the rate of formation of NO$_2$ and the rate of decomposition of N$_2$O$_5$ in the reaction 2N$_2$O$_5$ -> 4NO$_2$ + O$_2$?
What is the relationship between the rate of formation of NO$_2$ and the rate of decomposition of N$_2$O$_5$ in the reaction 2N$_2$O$_5$ -> 4NO$_2$ + O$_2$?
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What does the instantaneous rate of a reaction represent?
What does the instantaneous rate of a reaction represent?
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How is the instantaneous rate of a reaction determined graphically?
How is the instantaneous rate of a reaction determined graphically?
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In the expression Rate = $\frac{\Delta[O_2]}{\Delta t}$, what does $\Delta[O_2]$ represent?
In the expression Rate = $\frac{\Delta[O_2]}{\Delta t}$, what does $\Delta[O_2]$ represent?
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According to the provided information, how does the average rate of formation of O$_2$ change over time?
According to the provided information, how does the average rate of formation of O$_2$ change over time?
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What is the primary requirement for a collision between reactant molecules to result in a chemical reaction?
What is the primary requirement for a collision between reactant molecules to result in a chemical reaction?
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What is the 'transition state' or 'activated complex' in a chemical reaction?
What is the 'transition state' or 'activated complex' in a chemical reaction?
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How does a catalyst influence the activation energy of a chemical reaction?
How does a catalyst influence the activation energy of a chemical reaction?
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According to the Arrhenius equation, what is the general relationship between the rate constant and absolute temperature?
According to the Arrhenius equation, what is the general relationship between the rate constant and absolute temperature?
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In a multi-step reaction mechanism, what role does a catalyst play?
In a multi-step reaction mechanism, what role does a catalyst play?
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What is required to calculate the half-life of a reaction?
What is required to calculate the half-life of a reaction?
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What is the relationship between each successive half-life in a zero-order reaction?
What is the relationship between each successive half-life in a zero-order reaction?
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Which statement is true regarding the half-life of a first-order reaction?
Which statement is true regarding the half-life of a first-order reaction?
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How does the half-life change during the progression of a second-order reaction?
How does the half-life change during the progression of a second-order reaction?
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For a zero-order reaction, if the initial concentration is $[A]0$ and the rate constant is $k$, what is the expression for half-life ($t{1/2}$)?
For a zero-order reaction, if the initial concentration is $[A]0$ and the rate constant is $k$, what is the expression for half-life ($t{1/2}$)?
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What is the relationship between half-life and the rate constant in a first order reaction?
What is the relationship between half-life and the rate constant in a first order reaction?
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In a second-order reaction, where rate constant is $k$ and initial concentration is $[A]_0$, what is the equation for half-life?
In a second-order reaction, where rate constant is $k$ and initial concentration is $[A]_0$, what is the equation for half-life?
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A radioactive element decays following which order kinetics?
A radioactive element decays following which order kinetics?
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Which of the following statements regarding the half-life of different reaction orders is correct?
Which of the following statements regarding the half-life of different reaction orders is correct?
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What does 'k' represent in the half-life equations?
What does 'k' represent in the half-life equations?
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What is the primary characteristic of a radioisotope's half-life?
What is the primary characteristic of a radioisotope's half-life?
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Given the reaction mechanism:
(1) $H_2(g) + ICl(g) \rightarrow HI(g) + HCl(g)$
(2) $HI(g) + ICl(g) \rightarrow I_2(g) + HCl(g)$.
What is the role of $HI$ in this mechanism?
Given the reaction mechanism: (1) $H_2(g) + ICl(g) \rightarrow HI(g) + HCl(g)$ (2) $HI(g) + ICl(g) \rightarrow I_2(g) + HCl(g)$. What is the role of $HI$ in this mechanism?
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For the elementary step $2A \rightarrow B$, what is the molecularity of this reaction?
For the elementary step $2A \rightarrow B$, what is the molecularity of this reaction?
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If a substance has a half-life of 10 days, what fraction of the original material will remain after 30 days?
If a substance has a half-life of 10 days, what fraction of the original material will remain after 30 days?
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What is the relationship between the stoichiometric coefficients in an elementary step and the rate law for that step?
What is the relationship between the stoichiometric coefficients in an elementary step and the rate law for that step?
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Which of the following scenarios would result in a faster decay rate?
Which of the following scenarios would result in a faster decay rate?
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If the initial concentration of a drug decreases from $1.0 \times 10^{-3}$ M to $0.5 \times 10^{-3}$ M in 4 hours, and from $0.5 \times 10^{-3}$ M to $0.25 \times 10^{-3}$ M in 4 hours, what can be said about the reaction?
If the initial concentration of a drug decreases from $1.0 \times 10^{-3}$ M to $0.5 \times 10^{-3}$ M in 4 hours, and from $0.5 \times 10^{-3}$ M to $0.25 \times 10^{-3}$ M in 4 hours, what can be said about the reaction?
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In a two-step reaction mechanism, the first step is slow and the second step is fast. Which step determines the overall rate of the reaction?
In a two-step reaction mechanism, the first step is slow and the second step is fast. Which step determines the overall rate of the reaction?
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A reaction involves the collision of three molecules of a single reactant. What is the molecularity of this step?
A reaction involves the collision of three molecules of a single reactant. What is the molecularity of this step?
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How does the half-life of a radioisotope relate to its decay rate?
How does the half-life of a radioisotope relate to its decay rate?
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Study Notes
Chemical Kinetics
- Chemical kinetics is the study of the speeds or rates of reactions.
- Reactions can be fast or slow.
- Thermodynamics predicts the direction of a reaction, while kinetics describes the speed.
Learning Objectives
- 12.1 Reaction Rates: Defining reaction rate, the change in concentration of a substance over time.
- 12.2 Rate Laws: An Introduction: Expresses how reaction rate changes with concentrations of reactants.
- 12.3 Determining the Form of the Rate Law: Determining the rate law using experimental methods.
- 12.4 The Integrated Rate Law: Expressing how the concentration of a reactant varies with time.
- 12.5 Reaction Mechanism: Sequence of steps in a reaction; intermediate species are formed and consumed.
- 12.6 A Model for Chemical Kinetics: Explains how chemical reactions occur. The collision model; activation energy and the transition state. Catalysts lower activation energy without being consumed.
Kinetics vs. Thermodynamics
- Thermodynamics deals with the spontaneity of a reaction.
- Kinetics is concerned with the speed of a reaction at certain conditions.
- Kinetics explains how quickly reactions reach a certain state.
Aims of Chemical Kinetics
- Macroscopic level: Defining rate, order, and rate law; examining how rates and orders are determined.
- Molecular level: Predicting reaction mechanisms by examining the bond-making and bond-breaking steps involved in conversion from reactants to products.
Reaction Rates
- Reaction rate is the change in concentration of a substance over time.
- Rate is always a positive quantity.
- The unit of rate is the change in concentration per unit of time.
How to Determine Reaction Rates
- Measuring concentrations of reactants and/or products over the reaction.
- Using physical properties like: pressure changes (for gases) and light absorbance (Beer's law) in a color-changing reaction.
Expressing Average Reaction Rates
- Reaction rate can be measured by changes in concentrations of reactants or products over time.
- Rate of formation of one substance is related to the rate of consumption of another substance based on the stoichiometry of the reaction.
The Rate Law: The Effect of Concentration on Reaction Rate
- The rate of a reaction depends on the concentration of one or more reactants.
- The reaction rate and concentration relationship is called the rate law.
- Rate = k[A]m[B]n
- k is the rate constant. It is specific to a given reaction and temperature. A larger value of k means a faster reaction.
- m and n are the orders of the reaction with respect to reactants A and B, respectively. The overall order of the reaction is equal to m + n.
The Rate Law: Determining Order of Reaction
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The order of the reaction is determined experimentally from the change in concentration of reactants.
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Zero order: Rate is independent of reactant concentration.
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First order: Rate is directly proportional to the concentration of one reactant.
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Second order: Rate is proportional to the square of the concentration of one reactant, or the product of the concentrations of two reactants.
Determining the Rate Law: Method of Initial Rates
- Measure initial rate of reaction with different reactant concentrations.
- Comparing results helps determine reaction orders with respect to each reactant.
Integrated Rate Laws: Concentration–Time Relationship
- Differential rate law describes reaction rate at a specific moment.
- Integrated rate law describes how reactant concentrations change over a period of time.
- The form of the integrated rate law depends on the order of the reaction.
- The integrated rate laws can be derived by integration of the differential rate laws. Graphing the data gives a straight line relationship if you create the correct plot (concentration-of-reactant versus time).
The Half-Life of a Reaction
- The half-life (t1/2) is time required for the reactant concentration to decrease to one-half its initial value.
- In Chemistry and medicine it is used to predict the stability of substances.
The Half-Life of Different Reaction Orders
- The equation for half-life will vary with the order of reaction.
Radioactive Decay
- Radioactive decay is the disintegration of an unstable atom to a more stable one with emission of radiation.
- Radioactive decay is first-order kinetics.
- The half-life of a radioisotope can be used to characterize its decay rate.
The Activation Energy
- Activation Energy (Ea) is the minimum energy necessary for a reaction to proceed.
- The transition state is a high-energy state involved in bond formation or breaking.
- The transition state is also called the activated complex.
Catalysts
- Catalysts speed up reactions by lowering activation energy.
- Catalysts are not consumed during the reaction.
Effect of Temperature Temperature dependence of reaction rates described by Arrhenius Equation.
- Higher temperatures result in faster reaction rates.
- The rate constant (k) increases exponentially with increasing temperature.
Determining the Activation Energy from Arrhenius Equation
- Using the Arrhenius equation, the slope of a plot of ln(k) versus 1/T (in Kelvin) gives the activation energy.
Temperature Effect on Rate Constant
- The Arrhenius equation relates the rate constant to temperature, activation energy, and the frequency factor.
- At different temperatures, the rate constant has different value.
Reaction Mechanisms
- Reaction mechanisms are the sequence of elementary steps that occur to form a product from reactant.
- Intermediates are species produced in elementary steps and consumed in later ones.
- Elementary steps: unimolecular, bimolecular, termolecular.
- The rate-determining step determines the overall rate of the reaction.
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Test your knowledge on chemical kinetics with this quiz! It covers the rate of change, factors affecting reaction rates, and the roles of catalysts among other essential concepts. Ideal for students studying chemical reaction dynamics.
