AP Chemistry Unit 8 - Acids and Bases Review

Introduction

• Presenter: Jeremy Krug
• Focus: Acids and Bases
• Additional resources available at UltimateReviewPacket.com

pH and pOH

• pH: negative log of the hydronium ion concentration
• pOH: negative log of the hydroxide ion concentration
• Interchangeable terms: H+ and hydronium

Ion Product Constant of Water (Kw)

• At 25°C, [H3O+] × [OH-] = 1 × 10⁻¹⁴
• Equation: pH + pOH = 14
• Neutral Solution: pH = pOH = 7
• Temperature dependence: Kw increases with temperature, affecting neutral pH

Strong Acids and Bases

• Strong Acids: Ionize completely, pH = -log[acid concentration]
• Example: 0.010 M nitric acid → pH = 2.00
• Strong Bases: Typically Group 1 and 2 hydroxides, pOH = -log[OH- concentration]
• Example: 0.010 M calcium hydroxide → pH = 12.30

Weak Acids and Bases

• Weak Acids: Reversible dissociation, equilibrium constant Ka
• pKa: negative log of Ka
• Weak Bases: React with water, equilibrium constant Kb
• pKb: negative log of Kb

Calculating pH for Weak Acids

• Use ICE Box method for equilibrium
• Percent Dissociation: (x/initial concentration) × 100

Acid-Base Reactions

• Strong Acid + Strong Base: pH = 7 if equal moles
• Weak Acid + Strong Base: Produces water and conjugate base (buffer)
• Mixing Strategies: Handle as strong acid/base if excess

Titrations

• Titration Curve: Volume of titrant vs. pH
• Equivalence Point: Moles of acid = moles of base
• Half Equivalence Point: pH = pKa of weak acid
• Polyprotic Acids: Multiple inflection points

Acid/Base Strength

• Strong acids have weak conjugate bases
• Bronsted-Lowry Concept: Base strength related to proton attraction
• Organic acid strength: Influenced by electronegative atoms like F or O

Indicators in Titrations

• Match indicator pKa to equivalence point pH

Buffers

• Consist of weak acid and conjugate base
• Henderson-Hasselbalch Equation: For buffer pH
• Buffer Capacity: Higher concentrations withstand more pH change

Solubility and pH

• pH affects solubility of ionic compounds (e.g., magnesium carbonate)
• Le Chatelier’s Principle: System responds to changes by shifting equilibrium

Conclusion

• Next Unit: Thermodynamics and Electrochemistry
• Encouragement to continue AP Chem studies with Jeremy Krug