98 Questions
What is the main difference between the potential energy diagrams of uncatalysed and catalysed endothermic reactions?
The uncatalysed reaction has a higher activation energy peak.
Which of the following statements about exothermic reactions is correct?
Exothermic reactions release energy, so the energy level of the products is lower than the energy level of the reactants.
What information can be determined from the difference in height between the reactants and products on the potential energy diagram?
The change in enthalpy (ΔH) of the reaction.
What is the purpose of the peak point on the potential energy diagram?
It represents the energy level of the activated complex.
How does the presence of a catalyst affect the potential energy diagram of a reaction?
The catalyst decreases the activation energy of the reaction.
What does the area under the curve from reactants to the peak point on the potential energy diagram represent?
The activation energy of the reaction.
Which of the following statements about the potential energy diagrams of uncatalysed and catalysed reactions is correct?
The uncatalysed and catalysed reactions have the same pathway on the diagram.
What does the X-axis of the potential energy diagram represent?
The progress of the reaction.
Which of the following statements about the potential energy diagram of an endothermic reaction is incorrect?
The area under the curve from reactants to the peak represents the change in enthalpy (ΔH).
How does the presence of a catalyst affect the potential energy diagram of an exothermic reaction?
The catalyst reduces the activation energy of the reaction.
What type of reaction absorbs energy, with products having higher energy than reactants?
Endothermic
Which term defines the minimum energy required for reactants to form products during a chemical reaction?
Activation energy
What represents the unstable arrangement of atoms at the peak of the activation energy barrier?
Activated complex
In which reaction is energy released, with reactants having higher energy levels than the products?
Exothermic
What is the role of catalysts in chemical reactions?
To decrease activation energy
Which represents a specific momentary mixture of reactants and products during a reaction?
Activated complex
What is the significance of activation energy in determining the rate of a reaction?
Lower activation energy leads to a faster reaction
Which term describes the energy barrier that must be overcome for a chemical reaction to proceed?
Activation energy
In which type of reaction are reactants requiring external energy to convert into products?
Endothermic
What does the activated complex represent during a chemical reaction?
An intermediate state at the peak of activation energy barrier
What is the primary function of activation energy in a chemical reaction?
To determine the rate of the reaction
How does a higher activation energy affect the reaction rate under the same conditions?
It decreases the reaction rate
What does the activated complex represent in a chemical reaction?
A midpoint where bonds are breaking and forming
Which of the following statements about the activated complex is true?
It has higher energy than the products
What is the primary function of a positive catalyst in a chemical reaction?
To lower the activation energy
How do positive catalysts increase the rate of a chemical reaction?
By allowing more reactant particles to reach the transition state
What is the primary function of a negative catalyst (inhibitor) in a chemical reaction?
To increase the activation energy
Which of the following diagrams is used to represent activation energy in a chemical reaction?
Potential energy diagrams
What is the relationship between activation energy and the energy of the activated complex?
The activation energy is higher than the energy of the activated complex
Which of the following statements about catalysts is false?
Catalysts are consumed during the reaction
What does the area under the curve from reactants to the peak point on the potential energy diagram represent?
The activation energy required for the reaction
What is the primary function of activation energy in a chemical reaction?
To determine the rate of the reaction
How does the presence of a catalyst affect the potential energy diagram of an exothermic reaction?
It decreases the activation energy and lowers the energy of the products
What term defines the minimum energy required for reactants to form products during a chemical reaction?
Activation energy
Which of the following statements about the potential energy diagram of an endothermic reaction is incorrect?
The potential energy of the products is lower than the potential energy of the reactants
What represents the unstable arrangement of atoms at the peak of the activation energy barrier?
The activated complex
How does a higher activation energy affect the reaction rate under the same conditions?
It decreases the reaction rate
What is the primary function of a negative catalyst (inhibitor) in a chemical reaction?
To increase the activation energy and slow down the reaction
Which type of reaction absorbs energy, with products having higher energy than reactants?
Endothermic reaction
What is the main difference between the potential energy diagrams of uncatalyzed and catalyzed endothermic reactions?
The activation energy is lower in the catalyzed reaction
What role do positive catalysts (catalysts) play in a chemical reaction?
Provide an alternative reaction pathway with lower activation energy
Which term best describes the activated complex in a chemical reaction?
Midpoint between reactants and products
How does a higher activation energy affect the rate of a reaction under the same conditions?
Slows down the reaction
What is the primary function of negative catalysts (inhibitors) in a chemical reaction?
Increase the activation energy
What information can be inferred from the difference in height between reactants and products on a potential energy diagram?
Activation energy value
What characteristic differentiates activated complexes from reactants and products in a chemical reaction?
Higher energy level
In a chemical reaction, what is the primary effect of a negative catalyst (inhibitor) on the rate of reaction?
Slows down the reaction
What do potential energy diagrams show in terms of chemical reactions?
$\Delta E$ values
'Isolating the activated complex is challenging due to its:' ...?
$\text{High energy level and instability}$
What is represented by the area under the curve from reactants to the peak point on a potential energy diagram?
The activation energy barrier for the reaction
In a potential energy diagram, what does the difference in height between the reactants and products represent?
The enthalpy change ($\Delta H$) of the reaction
What does the area under the curve from reactants to the peak point on the potential energy diagram represent?
The activation energy of the reaction
How does the presence of a catalyst affect the potential energy diagram of a reaction?
It lowers the activation energy peak, but the start and end points remain the same
What does the peak point on the potential energy diagram represent?
The activated complex
What is the primary function of activation energy in a chemical reaction?
To provide the energy required for the reaction to occur
How do positive catalysts increase the rate of a chemical reaction?
By lowering the activation energy barrier
What represents the unstable arrangement of atoms at the peak of the activation energy barrier?
The activated complex
Which term defines the minimum energy required for reactants to form products during a chemical reaction?
Activation energy
What is the role of catalysts in chemical reactions?
To lower the activation energy barrier
Which of the following statements about the potential energy diagrams of uncatalysed and catalysed reactions is correct?
The catalysed reaction has a lower activation energy peak than the uncatalysed reaction
What information can be determined from the difference in height between the reactants and products on the potential energy diagram?
The change in enthalpy (ΔH) of the reaction
Which of the following statements about the potential energy diagrams of uncatalysed and catalysed reactions is correct?
The catalysed reaction has a lower activation energy peak than the uncatalysed reaction.
What does the peak point on the potential energy diagram represent?
The activated complex
What is the primary function of a positive catalyst in a chemical reaction?
To decrease the activation energy of the reaction
What does the area under the curve from reactants to the peak point on the potential energy diagram represent?
The activation energy of the reaction
Which of the following statements about catalysts is false?
Catalysts are consumed during the reaction and must be replenished.
What is the main difference between the potential energy diagrams of uncatalysed and catalysed endothermic reactions?
The catalysed reaction has a lower activation energy peak.
What is the primary function of activation energy in a chemical reaction?
To determine the rate of the reaction
Which term best describes the activated complex in a chemical reaction?
The transition state
What does the X-axis of the potential energy diagram represent?
The course of the reaction, from reactants to products
What effect does a higher activation energy have on the rate of a reaction under the same conditions?
Decreases the rate of reaction
Which of the following characteristics best differentiates activated complexes from reactants and products?
Exists momentarily
What is the primary function of a positive catalyst in a chemical reaction?
Lowers the activation energy
Which term best describes the activated complex in a chemical reaction?
Midpoint between reactants and products
How do negative catalysts (inhibitors) affect a chemical reaction?
Increase the activation energy
What defines a positive catalyst (catalyst) in a chemical reaction?
Lowers the activation energy
In terms of chemical reactions, what does a negative catalyst (inhibitor) primarily do?
Stops or slows down the reaction
What is represented by a higher activation energy in a chemical reaction?
Slows down the reaction
What happens to the rate of a reaction when a negative catalyst is introduced?
Decreases
What role does a positive catalyst play in relation to activation energy?
Lowers activation energy
What is the primary characteristic that distinguishes the activated complex from the reactants and products during a chemical reaction?
It is a fleeting arrangement that quickly dissociates into products or reverts to reactants.
In the context of potential energy diagrams, what does the area under the curve from reactants to the peak point represent?
The activation energy required for the reaction to proceed.
How do positive catalysts increase the rate of a chemical reaction?
By lowering the activation energy of the reaction.
Which statement about the role of negative catalysts (inhibitors) in a chemical reaction is correct?
They increase the activation energy, thereby slowing down the reaction rate.
Which statement best describes the potential energy diagrams of uncatalyzed and catalyzed reactions?
The catalyzed reaction has a lower activation energy but the same enthalpy change.
According to the law of conservation of energy in chemical reactions, what is the relationship between energy changes and enthalpy changes?
Energy cannot be created or destroyed, and enthalpy changes account for energy transferred as heat or work.
Which statement accurately describes the characteristic of the activated complex during a chemical reaction?
It is a momentary arrangement that quickly dissociates into products or reverts to reactants.
In the context of potential energy diagrams, what does the difference in height between the reactants and products represent?
The enthalpy change $\Delta$H for the overall reaction.
Which statement accurately describes the significance of activation energy in determining the rate of a chemical reaction?
Lower activation energy results in a faster reaction rate under the same conditions.
Which statement accurately describes the role of positive catalysts in chemical reactions?
They lower the activation energy, thereby increasing the reaction rate.
What feature on a potential energy diagram represents the highest point on the curve, symbolizing the activated complex?
Peak point
In a catalysed exothermic reaction, what is the primary effect on the activation energy peak?
It decreases compared to the uncatalysed reaction
What does the X-axis represent on a potential energy diagram?
Course of the reaction
How are activated complexes different from reactants and products in a chemical reaction?
They have higher potential energy than reactants but lower than products
What aspect of a potential energy diagram highlights the difference made by the presence of a catalyst in a reaction?
Peak point
In an exothermic reaction, what does it signify if the curve ends below the initial energy level of the reactants?
The reaction is exothermic
What does the difference in height between reactants and products represent on a potential energy diagram?
Change in enthalpy of the reaction
Which term best describes the activated complex in terms of its stability during a chemical reaction?
Metastable
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