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Questions and Answers
Which represent a base and its conjugate acid (listed in that order)?
Which represent a base and its conjugate acid (listed in that order)?
A strong acid completely donates H+ to a base.
A strong acid completely donates H+ to a base.
True
A low pKa value indicates a strong acid.
A low pKa value indicates a strong acid.
True
What is the equilibrium constant (pKeq) of the following reaction?
What is the equilibrium constant (pKeq) of the following reaction?
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Which group will lose a proton first (i.e. is most acidic)?
Which group will lose a proton first (i.e. is most acidic)?
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Which pair has the stronger acid listed first (on left)? Select all that apply.
Which pair has the stronger acid listed first (on left)? Select all that apply.
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What is the general trend of acidity across a row in the periodic table?
What is the general trend of acidity across a row in the periodic table?
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What is the general trend of acidity down a column in the periodic table?
What is the general trend of acidity down a column in the periodic table?
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Which carbon atom is most acidic in the molecule below?
Which carbon atom is most acidic in the molecule below?
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Study Notes
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.
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Description
Test your understanding of Chapter 4 on Acids and Bases, focusing on key concepts like Brønsted-Lowry definitions, acid dissociation constants, and pH levels. This quiz covers the assigned readings and practice problems to enhance your grasp of acidity trends and their implications in chemistry.
