Factors Affecting Reaction Rate - MCAT Chemical and Physical Foundations of Biological Systems
Card 1 of 56
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
What factors, not depicted in the reaction diagram, are most likely to influence reaction rate?
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
What factors, not depicted in the reaction diagram, are most likely to influence reaction rate?
Tap to reveal answer
Reactant concentration, along with activation energy and temperature, is a major determinant in reaction rate, as demonstrated in Le Chatlier's principle.
Reactant concentration, along with activation energy and temperature, is a major determinant in reaction rate, as demonstrated in Le Chatlier's principle.
← Didn't Know|Knew It →
Given the above equation for a reaction, which statement must ALWAYS be true?
Given the above equation for a reaction, which statement must ALWAYS be true?
Tap to reveal answer
This question can be approached two different ways. One way is by looking at the equation, and the other is understanding what the variables in the equation represent.
-
The first method is understanding the equation. Because we must understand basic log and natural log functions, we know that the natural log of a fraction is a negative number. Additionally, because we know that a reaction is spontaneous when 
is negative, we can conclude that a reaction will be spontaneous when Q is less than Keq. R is a positive constant, and T cannot be negative.
-
A second approach to this question is understanding the variables in the equation. Keq is the ratio of product to reactant at equilibrium. Q is the reaction quotient, and represents the ratio of product to reactant at a given point in time. If Q is less than Keq, the reaction is still too far to the left, and is still reacting to reach equilibrium. Because the reaction is trying to reach equilibrium, it will continue to spontaneously react until it reaches that point.
This question can be approached two different ways. One way is by looking at the equation, and the other is understanding what the variables in the equation represent.
-
The first method is understanding the equation. Because we must understand basic log and natural log functions, we know that the natural log of a fraction is a negative number. Additionally, because we know that a reaction is spontaneous when
-
A second approach to this question is understanding the variables in the equation. Keq is the ratio of product to reactant at equilibrium. Q is the reaction quotient, and represents the ratio of product to reactant at a given point in time. If Q is less than Keq, the reaction is still too far to the left, and is still reacting to reach equilibrium. Because the reaction is trying to reach equilibrium, it will continue to spontaneously react until it reaches that point.
← Didn't Know|Knew It →
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
Reaction rates depend on reaction concentrations, as well as the reaction constant 
. The Arrhenius equation is used to calculate this constant. Which of the following factors is used in the Arrhenius equation?
I. Temperature
II. Activation energy
III. Reactant concentrations
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
Reaction rates depend on reaction concentrations, as well as the reaction constant
I. Temperature
II. Activation energy
III. Reactant concentrations
Tap to reveal answer
If you thought all of these factors are used in the Arrhenius equation, consider that the rate constant is independent of the reactant concentrations. The concentration effect is considered in the rate law by multiplying the concentrations by the constant, but the concentrations themselves are independent of the actual Arrhenius calculation.
The calculation shows that 
. In this equation, 
is the activation energy and 
is the temperature.
If you thought all of these factors are used in the Arrhenius equation, consider that the rate constant is independent of the reactant concentrations. The concentration effect is considered in the rate law by multiplying the concentrations by the constant, but the concentrations themselves are independent of the actual Arrhenius calculation.
The calculation shows that
← Didn't Know|Knew It →
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
The scientist in the passage calculates that, under experimental conditions, the gievn reaction releases 
before it comes to equilibrium.
Under the exact same conditions, another unknown reaction is studied. This second reaction releases 
before it comes to equilibrium.
Which of the following must be true?
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
The scientist in the passage calculates that, under experimental conditions, the gievn reaction releases
Under the exact same conditions, another unknown reaction is studied. This second reaction releases
Which of the following must be true?
Tap to reveal answer
The amount of energy released or absorbed by a reaction is independent of its rate. Rate is principally determined by the activation energy, while the inherent bond energies of reactants and products dictate thermodynamic changes. One cannot be used to predict the other.
The amount of energy released or absorbed by a reaction is independent of its rate. Rate is principally determined by the activation energy, while the inherent bond energies of reactants and products dictate thermodynamic changes. One cannot be used to predict the other.
← Didn't Know|Knew It →
Consider the energy diagram of a three-step chemical process shown below. Which step would have the fastest rate?
Consider the energy diagram of a three-step chemical process shown below. Which step would have the fastest rate?
Tap to reveal answer
The reaction with the fastest rate will have the lowest activation energy; the energy difference between the starting compound and the top of the energy barrier that must be overcome to proceed to the product should be the smallest. Of the given choices, the reaction proceeding from C to D has the lowest energy barrier, and hence will have the lowest activation energy and fastest reaction rate.
In contrast, the energy required to move from point A to point B has the largest energy barrier, and can be assumed to be the rate-limiting step.
The reaction with the fastest rate will have the lowest activation energy; the energy difference between the starting compound and the top of the energy barrier that must be overcome to proceed to the product should be the smallest. Of the given choices, the reaction proceeding from C to D has the lowest energy barrier, and hence will have the lowest activation energy and fastest reaction rate.
In contrast, the energy required to move from point A to point B has the largest energy barrier, and can be assumed to be the rate-limiting step.
← Didn't Know|Knew It →
In any given reaction, the rate-determining step .
In any given reaction, the rate-determining step .
Tap to reveal answer
Reaction rates, including the rate-determining step, can be altered with a change in conditions. This includes a change in temperature, a change in pressure, or the addition of a catalyst.
Reaction rates, including the rate-determining step, can be altered with a change in conditions. This includes a change in temperature, a change in pressure, or the addition of a catalyst.
← Didn't Know|Knew It →
For a multi-step chemical reaction, which of the following will reduce the reaction rate?
For a multi-step chemical reaction, which of the following will reduce the reaction rate?
Tap to reveal answer
For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.
For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.
← Didn't Know|Knew It →
What is the role of a catalyst in an reaction?
What is the role of a catalyst in an reaction?
Tap to reveal answer
A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.
A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.
← Didn't Know|Knew It →
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
What factors, not depicted in the reaction diagram, are most likely to influence reaction rate?
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
What factors, not depicted in the reaction diagram, are most likely to influence reaction rate?
Tap to reveal answer
Reactant concentration, along with activation energy and temperature, is a major determinant in reaction rate, as demonstrated in Le Chatlier's principle.
Reactant concentration, along with activation energy and temperature, is a major determinant in reaction rate, as demonstrated in Le Chatlier's principle.
← Didn't Know|Knew It →
Given the above equation for a reaction, which statement must ALWAYS be true?
Given the above equation for a reaction, which statement must ALWAYS be true?
Tap to reveal answer
This question can be approached two different ways. One way is by looking at the equation, and the other is understanding what the variables in the equation represent.
-
The first method is understanding the equation. Because we must understand basic log and natural log functions, we know that the natural log of a fraction is a negative number. Additionally, because we know that a reaction is spontaneous when is negative, we can conclude that a reaction will be spontaneous when Q is less than Keq. R is a positive constant, and T cannot be negative.
-
A second approach to this question is understanding the variables in the equation. Keq is the ratio of product to reactant at equilibrium. Q is the reaction quotient, and represents the ratio of product to reactant at a given point in time. If Q is less than Keq, the reaction is still too far to the left, and is still reacting to reach equilibrium. Because the reaction is trying to reach equilibrium, it will continue to spontaneously react until it reaches that point.
This question can be approached two different ways. One way is by looking at the equation, and the other is understanding what the variables in the equation represent.
-
The first method is understanding the equation. Because we must understand basic log and natural log functions, we know that the natural log of a fraction is a negative number. Additionally, because we know that a reaction is spontaneous when
-
A second approach to this question is understanding the variables in the equation. Keq is the ratio of product to reactant at equilibrium. Q is the reaction quotient, and represents the ratio of product to reactant at a given point in time. If Q is less than Keq, the reaction is still too far to the left, and is still reacting to reach equilibrium. Because the reaction is trying to reach equilibrium, it will continue to spontaneously react until it reaches that point.
← Didn't Know|Knew It →
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
Reaction rates depend on reaction concentrations, as well as the reaction constant . The Arrhenius equation is used to calculate this constant. Which of the following factors is used in the Arrhenius equation?
I. Temperature
II. Activation energy
III. Reactant concentrations
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
Reaction rates depend on reaction concentrations, as well as the reaction constant
I. Temperature
II. Activation energy
III. Reactant concentrations
Tap to reveal answer
If you thought all of these factors are used in the Arrhenius equation, consider that the rate constant is independent of the reactant concentrations. The concentration effect is considered in the rate law by multiplying the concentrations by the constant, but the concentrations themselves are independent of the actual Arrhenius calculation.
The calculation shows that . In this equation, is the activation energy and is the temperature.
If you thought all of these factors are used in the Arrhenius equation, consider that the rate constant is independent of the reactant concentrations. The concentration effect is considered in the rate law by multiplying the concentrations by the constant, but the concentrations themselves are independent of the actual Arrhenius calculation.
The calculation shows that
← Didn't Know|Knew It →
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
The scientist in the passage calculates that, under experimental conditions, the gievn reaction releases before it comes to equilibrium.
Under the exact same conditions, another unknown reaction is studied. This second reaction releases before it comes to equilibrium.
Which of the following must be true?
A scientist is studying a reaction, and places the reactants in a beaker at room temperature. The reaction progresses, and she analyzes the products via NMR. Based on the NMR readout, she determines the reaction proceeds as follows:
In an attempt to better understand the reaction process, she varies the concentrations of the reactants and studies how the rate of the reaction changes. The table below shows the reaction concentrations as she makes modifications in three experimental trials.
The scientist in the passage calculates that, under experimental conditions, the gievn reaction releases
Under the exact same conditions, another unknown reaction is studied. This second reaction releases
Which of the following must be true?
Tap to reveal answer
The amount of energy released or absorbed by a reaction is independent of its rate. Rate is principally determined by the activation energy, while the inherent bond energies of reactants and products dictate thermodynamic changes. One cannot be used to predict the other.
The amount of energy released or absorbed by a reaction is independent of its rate. Rate is principally determined by the activation energy, while the inherent bond energies of reactants and products dictate thermodynamic changes. One cannot be used to predict the other.
← Didn't Know|Knew It →
Consider the energy diagram of a three-step chemical process shown below. Which step would have the fastest rate?
Consider the energy diagram of a three-step chemical process shown below. Which step would have the fastest rate?
Tap to reveal answer
The reaction with the fastest rate will have the lowest activation energy; the energy difference between the starting compound and the top of the energy barrier that must be overcome to proceed to the product should be the smallest. Of the given choices, the reaction proceeding from C to D has the lowest energy barrier, and hence will have the lowest activation energy and fastest reaction rate.
In contrast, the energy required to move from point A to point B has the largest energy barrier, and can be assumed to be the rate-limiting step.
The reaction with the fastest rate will have the lowest activation energy; the energy difference between the starting compound and the top of the energy barrier that must be overcome to proceed to the product should be the smallest. Of the given choices, the reaction proceeding from C to D has the lowest energy barrier, and hence will have the lowest activation energy and fastest reaction rate.
In contrast, the energy required to move from point A to point B has the largest energy barrier, and can be assumed to be the rate-limiting step.
← Didn't Know|Knew It →
In any given reaction, the rate-determining step .
In any given reaction, the rate-determining step .
Tap to reveal answer
Reaction rates, including the rate-determining step, can be altered with a change in conditions. This includes a change in temperature, a change in pressure, or the addition of a catalyst.
Reaction rates, including the rate-determining step, can be altered with a change in conditions. This includes a change in temperature, a change in pressure, or the addition of a catalyst.
← Didn't Know|Knew It →
For a multi-step chemical reaction, which of the following will reduce the reaction rate?
For a multi-step chemical reaction, which of the following will reduce the reaction rate?
Tap to reveal answer
For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.
For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.
← Didn't Know|Knew It →
What is the role of a catalyst in an reaction?
What is the role of a catalyst in an reaction?
Tap to reveal answer
A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.
A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.
← Didn't Know|Knew It →
In any given reaction, the rate-determining step .
In any given reaction, the rate-determining step .
Tap to reveal answer
Reaction rates, including the rate-determining step, can be altered with a change in conditions. This includes a change in temperature, a change in pressure, or the addition of a catalyst.
Reaction rates, including the rate-determining step, can be altered with a change in conditions. This includes a change in temperature, a change in pressure, or the addition of a catalyst.
← Didn't Know|Knew It →
For a multi-step chemical reaction, which of the following will reduce the reaction rate?
For a multi-step chemical reaction, which of the following will reduce the reaction rate?
Tap to reveal answer
For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.
For a multi-step reaction, the rate-determining step is the step with the highest activation energy. Be careful not to confuse this with the energy transition state.
← Didn't Know|Knew It →
What is the role of a catalyst in an reaction?
What is the role of a catalyst in an reaction?
Tap to reveal answer
A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.
A catalyst is used to increase the rate of a reaction. By definition, it does so without being consumed during the reaction. Thus the choices that talk about decreasing the rate of reaction are wrong. Catalysts decrease the activation energy of a reaction.
← Didn't Know|Knew It →
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
What factors, not depicted in the reaction diagram, are most likely to influence reaction rate?
For any given chemical reaction, one can draw an energy diagram. Energy diagrams depict the energy levels of the different steps in a reaction, while also indicating the net change in energy and giving clues to relative reaction rate.
Below, a reaction diagram is shown for a reaction that a scientist is studying in a lab. A student began the reaction the evening before, but the scientist is unsure as to the type of the reaction. He cannot find the student’s notes, except for the reaction diagram below.
What factors, not depicted in the reaction diagram, are most likely to influence reaction rate?
Tap to reveal answer
Reactant concentration, along with activation energy and temperature, is a major determinant in reaction rate, as demonstrated in Le Chatlier's principle.
Reactant concentration, along with activation energy and temperature, is a major determinant in reaction rate, as demonstrated in Le Chatlier's principle.
← Didn't Know|Knew It →