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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1:48 minutes

Problem 1b

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?

Verified step by step guidance

Step 1: Understand the problem. The given values of ∆H and ∆S are for the phase change from liquid H2O to gaseous H2O. To find the values for the reverse process (gaseous to liquid H2O), we need to reverse the signs of both ∆H and ∆S because the direction of the process is reversed.

Step 2: Reverse the sign of ∆H. The given ∆H for liquid to gas is +9.72 kcal/mol (or +40.7 kJ/mol). For the reverse process (gas to liquid), ∆H will be -9.72 kcal/mol (or -40.7 kJ/mol).

Step 3: Reverse the sign of ∆S. The given ∆S for liquid to gas is -26.1 cal/(mol • K) (or -109 J/(mol • K)). For the reverse process (gas to liquid), ∆S will be +26.1 cal/(mol • K) (or +109 J/(mol • K)).

Step 4: Ensure unit consistency. The values for ∆H and ∆S are already provided in both kcal/mol and kJ/mol, so no further unit conversion is necessary.

Step 5: Summarize the results. For the change from gaseous to liquid H2O, ∆H = -9.72 kcal/mol (-40.7 kJ/mol) and ∆S = +26.1 cal/(mol • K) [+109 J/(mol • K)].

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Key Concepts

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

Enthalpy Change (∆H)

Enthalpy change (∆H) refers to the heat content change of a system during a process at constant pressure. In the context of phase changes, a positive ∆H indicates that heat is absorbed when a substance transitions from a liquid to a gas, while a negative ∆H indicates heat is released during the reverse process. For the transition from gas to liquid, ∆H will be the negative of the value given for the liquid to gas transition.

Entropy Change (∆S)

Entropy change (∆S) measures the degree of disorder or randomness in a system. A negative ∆S value, as seen in the transition from liquid to gas, indicates a decrease in disorder when moving from a gaseous state to a liquid state. Thus, for the reverse transition from gas to liquid, ∆S will be the negative of the value provided for the liquid to gas transition, reflecting the increase in order.

Thermodynamic Relationships

Thermodynamic relationships, particularly the principles of reversibility, dictate that the values of ∆H and ∆S for a process are equal in magnitude but opposite in sign when the process is reversed. This means that to find the values for the transition from gaseous to liquid H2O, one simply takes the negative of the given values for the liquid to gas transition, allowing for straightforward calculations in thermodynamic problems.

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Multiple Choice

Consider the combustion of butane gas and predict the signs of ΔS, ΔH and ∆G.

C₄H₁₀(g) + 13/2 O₂(g) ⟶ 4 CO₂(g) + 5 H₂O(g)

A particular reaction has ΔG = –350 kJ and ΔS = –350 J/K at 24°C. How much heat will be released/absorbed?

For a reaction in which ΔH = 125 kJ and ΔS = 325 J/K, determine the temperature in Celsius above which the reaction is spontaneous.

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)].

a. Is the change from liquid to gaseous H2O favored or unfavored by ∆H? By ∆S?

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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 two factors affect the spontaneity of a reaction?

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