AP Chemistry Unit 8 Review: Acids and Bases

Introduction

• Presented by Jeremy Krug
• Focus on pH, pOH, and ion concentrations
• Importance of sharing and subscribing to content

Key Concepts

pH and pOH

• pH = -log[H₃O⁺]
• pOH = -log[OH⁻]
• At 25°C: [H₃O⁺][OH⁻] = 1 x 10⁻¹⁴ (Kw)
• pH + pOH = 14
• Neutral solution: pH = pOH = 7.00
• Temperature impacts Kw and pH

Strong Acids and Bases

• Six strong acids; their pH = -log[acid concentration]
• Strong bases (Group I and II hydroxides); pOH = -log[OH⁻], then pH = 14 - pOH
• Group Two hydroxides have a 2:1 ratio

Weak Acids and Bases

• Weak acids dissociate reversibly; have equilibrium constant (Ka)
• pKa = -log(Ka)
• Weak bases form conjugate acid and OH⁻; equilibrium constant (Kb)
• pKb = -log(Kb)
• Use ICE box for equilibrium calculations

Mixing Acids and Bases

• Strong acid + strong base = neutral (pH 7), if moles are equal
• Weak acid + strong base = buffer if weak acid is excess
• Strong acid + weak base = buffer if weak base is excess
• Compare Ka and Kb for weak acid + weak base

Titration

• Titration curve: volume of titrant vs. pH
• Inflection point = equivalence point (moles acid = moles base)
• Halfway point = pH = pKa of weak acid
• Polyprotic acids: multiple inflection points

Strength of Acids and Bases

• Stronger acids dissociate more; weaker conjugate base
• Organic acids: electronegative atoms (fluorine) and oxygens increase strength
• Strong bases have weak conjugate acids
• Common weak bases contain N and H

Acid-Base Indicators

• Indicators are weak acids that change color at specific pH
• Select indicator based on equivalence point pH

Buffers

• Mixture of weak acid and conjugate base; resist pH change
• Henderson-Hasselbalch Equation for pH calculation
• Buffer capacity: affects how much acid/base can be absorbed without pH change

Conclusion

• Overview of Unit 8 Acids and Bases
• Teaser for Unit 9 on Thermodynamics and Electrochemistry

Additional Notes

• Understanding these concepts is crucial for AP Chemistry success
• Practice with titrations and buffer calculations helpful for mastery