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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4:06 minutes

Problem 38b

Textbook Question

For the reaction 2 Hg(l) + O₂(g) → 2 HgO(s), ∆H = –43 kcal/mol (–180 kJ/mol).
b. Under what conditions would you expect this process to be spontaneous?

Verified step by step guidance

Determine the thermodynamic criteria for spontaneity: A process is spontaneous when the Gibbs free energy change (ΔG) is negative. The relationship is given by 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.

Analyze the given data: The reaction has a negative enthalpy change (ΔH = -43 kcal/mol or -180 kJ/mol), indicating that it is exothermic. This means the system releases heat to the surroundings.

Consider the entropy change (ΔS): The reaction involves the combination of liquid mercury (Hg) and oxygen gas (O2) to form solid mercury(II) oxide (HgO). Since gases have higher entropy than solids, the entropy of the system likely decreases (ΔS < 0).

Evaluate the temperature dependence: Since ΔH is negative and ΔS is negative, the term

- T Δ S

becomes positive as temperature increases. For the reaction to remain spontaneous (ΔG < 0), the magnitude of ΔH must outweigh the positive

- T Δ S

term, which is more likely at lower temperatures.

Conclude the conditions for spontaneity: This reaction is expected to be spontaneous at lower temperatures where the exothermic enthalpy change (ΔH) dominates over the unfavorable entropy change (ΔS).

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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 process at constant temperature and pressure. A reaction is spontaneous if the change in Gibbs Free Energy (∆G) is negative. The relationship between enthalpy (∆H), entropy (∆S), and temperature (T) is given by the equation ∆G = ∆H - T∆S, where a negative ∆G indicates a spontaneous reaction.

Enthalpy and Exothermic Reactions

Enthalpy (H) is a measure of the total energy of a thermodynamic system, and reactions that release energy, such as the given reaction with ∆H = -43 kcal/mol, are termed exothermic. Exothermic reactions tend to favor spontaneity because they result in a decrease in enthalpy, which contributes to a negative ∆G under appropriate conditions, particularly at lower temperatures.

Entropy and Disorder

Entropy (S) is a measure of the disorder or randomness in a system. In general, processes that increase the entropy of the universe are favored. For the reaction 2 Hg(l) + O2 → 2HgO(s), the formation of a solid from liquids and gases typically results in a decrease in entropy, which can affect spontaneity. Understanding the balance between enthalpy and entropy is crucial for determining the conditions under which the reaction is spontaneous.

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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?

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