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Questions and Answers
For a reaction where the rate is proportional to the square of reactant A's concentration, what happens to the reaction rate if the concentration of A is quadrupled?
For a reaction where the rate is proportional to the square of reactant A's concentration, what happens to the reaction rate if the concentration of A is quadrupled?
- The rate increases by a factor of 16. (correct)
- The rate increases by a factor of 4.
- The rate increases by a factor of 8.
- The rate remains unchanged.
A reaction's rate equation is given by rate = k[A]^a[B]^b. What do 'a' and 'b' represent in this equation?
A reaction's rate equation is given by rate = k[A]^a[B]^b. What do 'a' and 'b' represent in this equation?
- The stoichiometric coefficients of A and B in the balanced equation.
- The partial pressures of gases A and B.
- The orders of reaction with respect to A and B, respectively. (correct)
- The equilibrium constants for reactants A and B, respectively.
A chemist wants to determine the order of a reaction with respect to a single reactant. Which graphical method would be most suitable?
A chemist wants to determine the order of a reaction with respect to a single reactant. Which graphical method would be most suitable?
- Plotting volume against temperature at constant pressure.
- Plotting the number of moles of product against the number of moles of reactant.
- Plotting pressure against volume at constant temperature.
- Plotting reaction rate against concentration of the reactant. (correct)
A reaction is found to be zero order with respect to reactant C. What does this imply about the reaction rate?
A reaction is found to be zero order with respect to reactant C. What does this imply about the reaction rate?
For a reaction with the rate equation rate = k[A]^2[B], what is the overall order of the reaction?
For a reaction with the rate equation rate = k[A]^2[B], what is the overall order of the reaction?
Which of the following plots can be used to deduce the order of reaction with respect to a single reactant?
Which of the following plots can be used to deduce the order of reaction with respect to a single reactant?
The rate equation for a reaction is rate = k[B]^2. What is the order of the reaction with respect to reactant A?
The rate equation for a reaction is rate = k[B]^2. What is the order of the reaction with respect to reactant A?
For a first-order reaction, if the initial concentration of a reactant is doubled, what happens to the half-life?
For a first-order reaction, if the initial concentration of a reactant is doubled, what happens to the half-life?
A reaction's half-life is observed to be constant regardless of the initial concentration. What can be concluded about the reaction order?
A reaction's half-life is observed to be constant regardless of the initial concentration. What can be concluded about the reaction order?
A reaction between reactants A and B is found to be first order with respect to A and zero order with respect to B. If the concentration of A is doubled and the concentration of B is tripled, what happens to the reaction rate?
A reaction between reactants A and B is found to be first order with respect to A and zero order with respect to B. If the concentration of A is doubled and the concentration of B is tripled, what happens to the reaction rate?
Consider a reaction where the rate equation is determined to be rate = k[A][B]^2. If the concentration of A is halved and the concentration of B is doubled, what is the resulting change in the reaction rate?
Consider a reaction where the rate equation is determined to be rate = k[A][B]^2. If the concentration of A is halved and the concentration of B is doubled, what is the resulting change in the reaction rate?
The half-life of a first-order reaction is 69.3 seconds. What is the rate constant (k) for this reaction?
The half-life of a first-order reaction is 69.3 seconds. What is the rate constant (k) for this reaction?
Under what conditions is the rate constant, k, considered constant for a given reaction?
Under what conditions is the rate constant, k, considered constant for a given reaction?
For a first-order reaction, what does a plot of concentration against time look like?
For a first-order reaction, what does a plot of concentration against time look like?
The rate constant of a first-order reaction is $3.465 \times 10^{-2} s^{-1}$. What is the half-life of the reaction?
The rate constant of a first-order reaction is $3.465 \times 10^{-2} s^{-1}$. What is the half-life of the reaction?
What is the half-life of a first-order reaction if it takes 10 minutes for the concentration of the reactant to decrease from 0.8 M to 0.4 M?
What is the half-life of a first-order reaction if it takes 10 minutes for the concentration of the reactant to decrease from 0.8 M to 0.4 M?
A reaction's rate is found to increase by a factor of 2.25 when the concentration of reactant X is increased by a factor of 1.5. What is the order of the reaction with respect to reactant X?
A reaction's rate is found to increase by a factor of 2.25 when the concentration of reactant X is increased by a factor of 1.5. What is the order of the reaction with respect to reactant X?
Which statement accurately describes how reaction rate is typically measured for rate equations?
Which statement accurately describes how reaction rate is typically measured for rate equations?
The rate of a reaction is found to be directly proportional to the square root of the concentration of reactant B. What is the order of the reaction with respect to B?
The rate of a reaction is found to be directly proportional to the square root of the concentration of reactant B. What is the order of the reaction with respect to B?
What are the units for the rate of a reaction, as used in rate equations?
What are the units for the rate of a reaction, as used in rate equations?
For the reaction $A + B \rightarrow C$, doubling the concentration of A doubles the reaction rate, while tripling the concentration of B has no effect on the rate. What is the rate equation?
For the reaction $A + B \rightarrow C$, doubling the concentration of A doubles the reaction rate, while tripling the concentration of B has no effect on the rate. What is the rate equation?
A chemist proposes a rate equation based on experimental data. What must be true of this equation?
A chemist proposes a rate equation based on experimental data. What must be true of this equation?
The rate of a reaction is $0.002$ mol dm$^{-3}$ s$^{-1}$ when the concentration of reactant A is $0.1$ mol dm$^{-3}$. If the reaction is first order with respect to A, what is the rate constant, k?
The rate of a reaction is $0.002$ mol dm$^{-3}$ s$^{-1}$ when the concentration of reactant A is $0.1$ mol dm$^{-3}$. If the reaction is first order with respect to A, what is the rate constant, k?
Why can't the order of a reaction be determined simply by looking at the balanced chemical equation?
Why can't the order of a reaction be determined simply by looking at the balanced chemical equation?
Flashcards
Rate proportional to [A]^2
Rate proportional to [A]^2
The rate of a reaction is proportional to the square of the concentration of reactant A. Doubling [A] quadruples the rate.
Rate Equation
Rate Equation
An equation showing how the rate of reaction depends on the concentrations of reactants.
Order of Reaction
Order of Reaction
The power to which a reactant's concentration is raised in the rate equation. Indicates how the concentration affects rate.
Zero Order with respect to A
Zero Order with respect to A
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Overall Order of Reaction
Overall Order of Reaction
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What is an overall second order reaction?
What is an overall second order reaction?
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What is an overall first order reaction?
What is an overall first order reaction?
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Rate Constant (k)
Rate Constant (k)
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Half-life
Half-life
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First-order reaction (half-life)
First-order reaction (half-life)
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First-order half-life characteristic
First-order half-life characteristic
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Half-life equation (first-order)
Half-life equation (first-order)
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Rate constant equation (first-order)
Rate constant equation (first-order)
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Half-life example 1
Half-life example 1
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Half-life example 2
Half-life example 2
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Half-life units
Half-life units
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Reaction Rate
Reaction Rate
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Experimental Orders
Experimental Orders
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First Order
First Order
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[A]
[A]
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Study Notes
- Students should be able to describe rate constant and order of reaction
- Students should be able to perform calculations to determine the rate constant
Reaction Rate Measurement
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A chemical reaction transforms reactants into products through changes in chemical bonds, classified into combination, decomposition, and displacement reactions.
The reaction rate quantifies how fast the reactants convert into products over time and is influenced by several factors including concentration, temperature, surface area, and the presence of catalysts. Understanding the dynamics of these reactions is crucial in fields such as biochemistry, pharmacology, and industrial chemistry, as it aids in optimizing conditions for desired reaction outcomes and efficient production processes.
rate can be measured by monitoring gas production or reactant concentration changes
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The rate is usually measured by how fast the concentration of one of the reactants is decreasing
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The rate of a reaction is measured in terms of how fast the concentration of one of the reactants is falling, with units being mol dm-3 s-1.
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rate of reaction = change in concentration of reactants or products / time taken for the change
Orders of Reaction
- Orders of reaction are determined empirically, not derived from the reaction equation.
- If the rate of a reaction is proportional to the concentration of reactant A, doubling [A] doubles the rate.
- Rate α [A] can be written as Rate = k[A], where k is the rate constant
- In symbol terms, Rate α [A]^2 is written as Rate = k[A]^2
- By doing experiments with A and B, reaction rate relates to concentration
Rate Equation
- Rate = k[A]^a [B]^b
- The powers to which concentrations are raised indicate the orders of reaction with respect to each reactant.
- Orders of reaction will most likely be either 0, 1 or 2
Understanding Reaction Order
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If the order of reaction with respect to A is 0, the concentration of A does not affect the rate of reaction.
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Overall order of the reaction equals the sum of the individual orders
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Example 1: Rate = k[A][B], overall order of reaction is Second order
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Example 2: Rate = k[B]^2, the reaction is zero order with respect to A and Second order overall
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Example 3: Rate = k[A], the reaction is first order with respect to A and first order overall
Rate Constant
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The rate constant (k) is crucial in chemical kinetics as it measures reaction speed at a specific temperature and links reaction rate to reactant concentrations. Influenced by temperature, reactant nature, and catalysts, it is expressed in the rate law [Rate = k [A]^m [B]^n].nts.
remains constant only if the changing variable is the concentration of reactants, not the temperature.
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Order of reaction can be deduced by plotting of graph of reaction rate against concentration of reactant.
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Order of reaction can also be deduced by plotting a graph of concentration of reactant against time
Half-LifeD
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Half-life is the time it takes for the concentration of a substance to fall to half of its original value.
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First order reaction half-life remains constant regardless of the initial concentration.
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Concentration vs. time graph can be used to determine half-life
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Zero order reaction will be a straight line
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First order reaction will be a curve with a constant half-life
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Other order of reaction will be a curve with a non-constant half-life, this means only first order reactions have a constant half-life.
Half life formula
- k = ln 2/ t1/2 which can be expressed as k = 0.693 / t1/2
- t1/2 = 0.693 / k
Example calculation
- Example 1: In the context of a first-order reaction, if the half-life is determined to be 300 seconds, this measurement indicates the time taken for the concentration of the reactant to decrease to half of its initial value. To find the rate constant (k) for this reaction, the equation k = (0.693/half-life) is utilized. Thus, k = (0.693/300) results in a rate constant of 0.00231 s-1, illustrating the relationship between half-life and the speed of the reaction.
- Example 2: Similarly, for a first-order reaction where the rate constant is given as 7.70 x 10-4 s-1, the half-life can be calculated using the same equation. Here, t1/2 = 0.693 / (7.70 x 10-4) yields a half-life of 900 seconds, indicating how long it takes for half of the reactants to be converted into products in this reaction.
- Rate= k[A][B]^2 can be deduced by keeping [B] concentration constant between experiments to find out how concentration of A affects the rate
- By keeping [A] concentration constant between experiments concentration of B can be deduced
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Description
Understand rate constants, reaction orders, and reaction rate measurements. Learn how to measure reaction rates by monitoring gas production or reactant concentration changes and calculating rate constants. Explore the empirical determination of reaction orders and their relationship to reactant concentrations.
