Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

7. Energy, Rate and Equilibrium

Gibbs Free Energy (Simplified)

GOB Chemistry

7. Energy, Rate and Equilibrium

Gibbs Free Energy (Simplified)

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2:27 minutes

Problem 33

Textbook Question

What two factors affect the spontaneity of a reaction?

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The spontaneity of a reaction is determined by the Gibbs free energy change (ΔG), which is calculated using the equation:

Δ G = Δ H - T Δ S

, where ΔH is the enthalpy change, T is the temperature in Kelvin, and ΔS is the entropy change.

The first factor is the enthalpy change (ΔH). A reaction tends to be spontaneous if it releases energy (exothermic, ΔH < 0). If the reaction absorbs energy (endothermic, ΔH > 0), it may still be spontaneous depending on the other factors.

The second factor is the entropy change (ΔS). A reaction tends to be spontaneous if it increases the disorder of the system (ΔS > 0). A decrease in entropy (ΔS < 0) may still allow spontaneity if other conditions are favorable.

Temperature (T) plays a critical role in determining spontaneity because it affects the relative importance of the entropy term (

T Δ S

) in the Gibbs free energy equation. At higher temperatures, the entropy term becomes more significant.

In summary, the two main factors affecting the spontaneity of a reaction are the enthalpy change (ΔH) and the entropy change (ΔS), with temperature (T) influencing their relative contributions to the Gibbs free energy (ΔG).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Gibbs Free Energy

Gibbs Free Energy (G) is a thermodynamic potential that helps predict the spontaneity of a reaction. A reaction is spontaneous if the change in Gibbs Free Energy (ΔG) is negative, indicating that the process can occur without external energy input. The relationship between enthalpy, entropy, and temperature is crucial in determining ΔG, making it a central concept in thermodynamics.

Enthalpy

Enthalpy (H) is a measure of the total heat content of a system and is crucial in understanding the energy changes during a reaction. A reaction can be exothermic (releases heat, ΔH < 0) or endothermic (absorbs heat, ΔH > 0). The change in enthalpy affects the spontaneity of a reaction, as exothermic reactions tend to favor spontaneity under constant pressure.

Entropy

Entropy (S) is a measure of the disorder or randomness in a system. According to the second law of thermodynamics, the total entropy of an isolated system can never decrease over time. For a reaction to be spontaneous, the change in entropy (ΔS) must be positive, which often occurs when products are more disordered than reactants, contributing to the overall spontaneity when combined with enthalpy changes.

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Related Practice

Textbook Question

The change of state from liquid H₂O to gaseous H₂O has ∆H = +9.72 kcal/mol(+40.7 kJ/mol) and ∆S = -26.1 cal/(mol • K) [-109 J/(mol •K)].

b. What are the values of ∆H and ∆S (in kcal/mol and kJ/mol) for the change from gaseous to liquid H2O?

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Textbook Question

Two curves are shown in the following energy diagram:

b. Which curve represents the spontaneous reaction, and which the nonspontaneous?

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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).

b. Is the reaction likely to be spontaneous at all temperatures, nonspontaneous at all temperatures, or spontaneous at some but nonspontaneous at others?

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Textbook Question

a. What is the sign of ∆S for the reaction?

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Textbook Question

What is the difference between an exothermic reaction and an exergonic reaction?

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Textbook Question

Under what conditions might a reaction be endothermic but exergonic? Explain.