Chemistry Chapter 4: Acids and Bases Quiz

Chapter 4: Acids and Bases

• Key Concepts: Brønsted-Lowry acids and bases, acid dissociation constants (pKa), acidity trends (electronegativity, atom size, hybridization at carbon, resonance delocalization, inductive effects).
• Assigned Reading: All of Chapter 4 except sections 4.2B, 4.2C, 4.5, and 4.7.
• Practice Problems: From the 8th edition textbook, chapter 4, problems 4.1, 2, 5, 6, and end-of-chapter problems 4.10, 11, 13, 15, 26, 29, 38, 47 (45), 54 (48), 55 (49), 58 (52), and 59 (53).

Chapter 4.1-4.4: Acids, Bases, and pKas

• pH and Hydrangeas: pH scale relates to acidity and alkalinity, with a lower pH indicating acidity and a higher pH indicating alkalinity. Hydrangeas flower color changes based on pH levels of soil.
• Reading: Chapter 4.1, 4.2A, 4.3, and 4.4.
• Textbook Problems: 4.1, 4.2, 4.5, 4.6, 4.10, 4.11, 4.15, 4.26, and 4.29.

Brønsted-Lowry Acids and Bases

• Definitions: Acids are proton donors, bases are proton acceptors.
• Conjugate Pairs: Conjugate base formed when an acid loses a proton; conjugate acid formed when a base accepts a proton.
• Strong vs. Weak: Strong acids/bases completely donate/accept protons; weak acids/bases don't.

Acid Dissociation Constants and pKa

• pKa and Strength: pKa values measure the strength of an acid; lower pKa indicates a stronger acid.
• Equilibrium Constant (Ka): Used to express the strength of an acid, relates to concentrations of products and reactants during the acid dissociation process.
• Relationship between pKa and Ka: The lower the pKa value, the stronger the acid, and the higher its Ka value.

pKa Values for Common Acids

• A table of pKa values for various common acids. Refer to the provided table (Table 4.1).

Predicting Equilibria

• Using pKa values: Determine whether an acid-base reaction will occur by comparing the pKa of the acid to the pKa of the conjugate acid or base.

iClicker Questions (Ch4#1, #2, #3, #4)

• Question 1: Select the conjugate acid-base pair.
• Question 2: Calculate equilibrium constant (pKeq).
• Question 3: Identify the most acidic proton in a molecule.
• Question 4: Select the stronger acid from pairs.

Acidity Trends: An Overview

• Factors affecting stability: Electronegativity, atom size, hybridization, resonance, inductive effects, electrostatic stabilization influence stability of anions during acid dissociation.

Acidity Trends: Identifying Factors

• Electronegativity: More electronegative elements stabilize negative charges better (stabilizing conjugate bases, strengthening acids)
• Atom Size: Larger atoms accommodate the negative charge better (more stable, stronger acid)
• Hybridization: More s-character, more stable.
• Resonance: Delocalization of the negative charge (e.g., via resonance) stabilizes conjugate base improving acid strength.
• Inductive effects: Electron-withdrawing groups stabilize the negative charge (strengthening the acid).

Acidity Trends: Specific Examples

• Acidity based on functional groups (alcohols, thiols, carboxylic acids, etc.,): Provide details on acid strength trends for these groups based on structure considerations & the pKa values. Refer to the table and examples provided.
• Organic Acidity examples and trends: Examples and comparative details on different organic acid structures and stability trends; focus on determining the most acidic proton.
• Cyclic dipeptides: Examples provided.
• Cholic Acid: example provided

Additional notes

• Consider the provided images and tables for specific details and examples.