Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

6. Thermodynamics and Kinetics

Gibbs Free Energy

Organic Chemistry

6. Thermodynamics and Kinetics

Gibbs Free Energy

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6:59 minutes

Problem 24d

Textbook Question

For the following acid–base reaction, (d) calculate ∆G° at 298 K.

Verified step by step guidance

Step 1: Identify the acid and base in the reaction. Determine the conjugate acid and conjugate base formed after the reaction. This will help in understanding the equilibrium of the reaction.

Step 2: Use the pKa values of the acid and conjugate acid to calculate the equilibrium constant (K_eq) for the reaction. The relationship between pKa and K_eq is given by \( K_{eq} = 10^{\Delta pKa} \), where \( \Delta pKa = pKa_{acid} - pKa_{conjugate acid} \).

Step 3: Recall the relationship between \( \Delta G^\circ \) and \( K_{eq} \): \( \Delta G^\circ = -RT \ln K_{eq} \). Here, \( R \) is the gas constant (8.314 J/mol·K), \( T \) is the temperature in Kelvin (298 K), and \( K_{eq} \) is the equilibrium constant calculated in Step 2.

Step 4: Substitute the values of \( R \), \( T \), and \( K_{eq} \) into the equation \( \Delta G^\circ = -RT \ln K_{eq} \). Ensure that \( K_{eq} \) is expressed in a form suitable for logarithmic calculation.

Step 5: Perform the calculation to determine \( \Delta G^\circ \). The result will be in joules per mole (J/mol). If needed, convert the value to kilojoules per mole (kJ/mol) by dividing by 1000.

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Key Concepts

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

Gibbs Free Energy (∆G)

Gibbs Free Energy (∆G) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. It is a crucial concept in predicting the spontaneity of a reaction; a negative ∆G indicates a spontaneous process, while a positive ∆G suggests non-spontaneity. The standard Gibbs free energy change (∆G°) is calculated under standard conditions (1 atm, 1 M concentration, and 298 K).

Acid-Base Reactions

Acid-base reactions involve the transfer of protons (H⁺ ions) between reactants. In these reactions, acids donate protons, while bases accept them. Understanding the strength of acids and bases, as well as their dissociation constants (Ka and Kb), is essential for calculating the equilibrium position and the Gibbs free energy change associated with the reaction. The reaction's direction and extent can significantly influence the overall energy change.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction. It is related to the standard Gibbs free energy change by the equation ∆G° = -RT ln(K), where R is the universal gas constant and T is the temperature in Kelvin. Knowing K allows for the calculation of ∆G° and provides insight into the favorability of the reaction under standard conditions.

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Related Practice

Textbook Question

Calculate ∆G°, ∆H°, and ∆S° for the following acid–base reactions. Rationalize the value of ∆H° based on the structure of the conjugate bases. [Assume T = 298 K.]

(a)

Textbook Question

Calculate ∆G°, ∆H°, and ∆S° for the following acid–base reactions. Rationalize the value of ∆H° based on the structure of the conjugate bases. [Assume T = 298 K.]

(c)

Textbook Question

Write the rate law for the following reaction and identify which molecules are present in the rate-determining step. Draw a possible transition state and propose a mechanism.

Textbook Question

Third-order reactions are rare. Why do you think that is?

Textbook Question

For the following acid–base reaction, (e) calculate ∆G° at 273 K.

Textbook Question

For the following acid–base reaction, (f) calculate ∆G° at 373 K.

Textbook Question

For each of the following acid–base reactions, (iii) calculate ∆G°. If a pK_a is not one of the ten common ones we learned in Chapter 4, it will be given to you.

(a)

Textbook Question

Using the bond-dissociation energies in Table 5.6 (see Section 5.3.1), estimate the equilibrium constant of the following reaction at 298 K.

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