Table of contents

1. Matter and Measurements4h 29m
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 35m
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. Amines38m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 46m
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

Entropy (Simplified)

GOB Chemistry

7. Energy, Rate and Equilibrium

Entropy (Simplified)

3:28 minutes

Problem 38McMurry - 8th Edition

Textbook Question

For the reaction 2 Hg(l) O2 → 2HgO(s), ∆H = -43 kcal/mol (-180 kJ/mol). Does entropy increase or decrease in this process? Explain.

Verified step by step guidance

Identify the states of matter for each substance in the reaction: Hg is a liquid, O2 is a gas, and HgO is a solid.

Consider the change in the number of moles of gas: The reaction starts with 1 mole of O2 gas and ends with no gas, indicating a decrease in the number of gas molecules.

Recall that entropy (S) is a measure of disorder or randomness in a system. Gases have higher entropy than liquids and solids due to their higher degree of freedom and movement.

Since the reaction involves the conversion of a gas (O2) to a solid (HgO), the system becomes more ordered, leading to a decrease in entropy.

Conclude that the entropy decreases in this process because the gaseous reactant is converted into a solid product, reducing the overall disorder of the system.

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Key Concepts

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

Enthalpy (∆H)

Enthalpy is a thermodynamic property that reflects the total heat content of a system. In the given reaction, the negative value of ∆H indicates that the reaction is exothermic, meaning it releases heat. This release of energy can influence the entropy of the system, as it often leads to a decrease in disorder when heat is lost.

Entropy (S)

Entropy is a measure of the disorder or randomness in a system. In chemical reactions, an increase in entropy typically occurs when the number of gas molecules increases or when solids and liquids are converted into gases. Conversely, a decrease in entropy happens when a system becomes more ordered, such as when gaseous reactants form solid products.

Gibbs Free Energy (∆G)

Gibbs Free Energy combines enthalpy and entropy to determine the spontaneity of a reaction. The relationship is given by the equation ∆G = ∆H - T∆S, where T is the temperature in Kelvin. For a reaction to be spontaneous, ∆G must be negative, which can occur if the enthalpy change is negative and the entropy change is also negative, as in the case of the formation of solid HgO from liquid Hg and O2.