Textbook Question
Is the total enthalpy (H) of the reactants for an endothermic reaction greater than or less than the total enthalpy of the products?
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Ch.7 Chemical Reactions: Energy, Rate and Equilibrium
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 7, Problem 21b
Two curves are shown in the following energy diagram:
b. Which curve represents the spontaneous reaction, and which the nonspontaneous?
Verified step by step guidance1
Examine the energy diagram. The y-axis represents free energy, and the x-axis represents the progress of the reaction. The two curves (blue and yellow) show the energy changes during two different reactions.
Identify the starting and ending points of each curve. The starting point represents the reactants' free energy, and the ending point represents the products' free energy.
Determine the change in free energy (ΔG) for each curve. ΔG is calculated as the difference between the free energy of the products and the reactants. If ΔG < 0 (negative), the reaction is spontaneous. If ΔG > 0 (positive), the reaction is nonspontaneous.
Analyze the blue curve: The products' free energy is lower than the reactants' free energy, indicating a negative ΔG. This means the blue curve represents a spontaneous reaction.
Analyze the yellow curve: The products' free energy is higher than the reactants' free energy, indicating a positive ΔG. This means the yellow curve represents a nonspontaneous reaction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Free Energy
Free energy, often represented as Gibbs free energy (G), is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. A decrease in free energy indicates a spontaneous reaction, while an increase suggests nonspontaneity. Understanding free energy is crucial for predicting the direction of chemical reactions.
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Gibbs Free Energy (Simplified) Concept 3
Spontaneous Reactions
A spontaneous reaction is one that occurs without the need for external energy input once initiated. In an energy diagram, spontaneous reactions typically show a decrease in free energy as reactants convert to products. This is represented by a curve that ends at a lower free energy level than it started, indicating that the reaction can proceed naturally.
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Energy Diagrams
Energy diagrams graphically represent the energy changes during a chemical reaction. They plot free energy against the progress of the reaction, illustrating the energy of reactants, products, and the activation energy barrier. The shape of the curves in the diagram helps identify whether a reaction is spontaneous or nonspontaneous based on the relative positions of the reactants and products.
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Related Practice
Textbook Question
The following diagram portrays a reaction of the type A(s) → B(g) + C(g), where the different-colored spheres represent different molecular structures. Assume that the reaction has ∆H = +9.1 kcal/mol (+38.1 kJ/mol).
b. Is the reaction likely to be spontaneous at all temperatures, nonspontaneous at all temperatures, or spontaneous at some but nonspontaneous at others?
Textbook Question
What effect do the listed changes have on the position of the equilibrium in the reaction of carbon with hydrogen?
C(s) + 2 H2(g) ⇌ CH4(g) ∆H = -18 kcal/mol (-75kJ/mol)
b. Increasing pressure by decreasing volume
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Textbook Question
What effect do the listed changes have on the position of the equilibrium in the reaction of carbon with hydrogen?
C(s) + 2 H2(g) ⇌ CH4(g) ∆H = -18 kcal/mol (-75kJ/mol)
c. Allowing CH4 to escape continuously from the reaction vessel
1
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Textbook Question
What effect do the listed changes have on the position of the equilibrium in the reaction of carbon with hydrogen?
C(s) + 2 H2(g) ⇌ CH4(g) ∆H = -18 kcal/mol (-75kJ/mol)
a. Increasing temperature
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Textbook Question
The following diagram portrays a reaction of the type A(s) → B(g) + C(g), where the different-colored spheres represent different molecular structures. Assume that the reaction has ∆H = +9.1 kcal/mol (+38.1 kJ/mol).
a. What is the sign of ∆S for the reaction?