Weak Acid and Base Equilibria

Sophie Anderson
7 min read
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Study Guide Overview
This study guide covers acids and bases, focusing on weak acids and bases. It reviews acid-base definitions (Arrhenius, Bronsted-Lowry), strong/weak acid/base identification, and the concept of equilibrium. It explains Ka and Kb expressions and calculations, including the use of ICE tables for determining pH. Finally, it provides practice questions and exam tips covering common question types, time management strategies, and high-priority topics for the AP Chemistry exam.
#AP Chemistry: Acids and Bases - The Night Before 🌙
Hey, future chemist! Let's get you prepped and confident for your AP Chemistry exam. We're diving into the world of acids and bases, focusing on those tricky weak ones. Buckle up, and let's make this stick!
#Acid-Base Basics: Strong vs. Weak
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Defining Acids and Bases
- Arrhenius Definition: Acids produce H⁺ ions in water, and bases produce OH⁻ ions.
- Bronsted-Lowry Definition: Acids are proton (H⁺) donors, and bases are proton acceptors.
- For our purposes, we'll primarily use the Arrhenius definition to keep things simple.
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Strong Acids and Bases
- Strong Acids: Completely dissociate in water (virtually 100% ionization).
- Memorize these 7: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₃, HClO₄
- They break down into H⁺ and their conjugate base (e.g., HCl → H⁺ + Cl⁻).
- Strong Bases: Also completely dissociate in water.
- Alkali and alkaline earth metal hydroxides: NaOH, KOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂
- They break down into metal cation and OH⁻ (e.g., NaOH → Na⁺ + OH⁻).
Conjugates of Strong Acids/Bases: Their conjugates (like Cl⁻ from HCl) are so weak they're practically neutral. They don't contribute to the pH.
Image: Visual representation of strong acids fully dissociating and weak acids partially dissociating.
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Weak Acids and Bases
- Weak Acids/Bases: Incompletely dissociate in water. They exist in equilibrium between the undissociated and dissociated forms.
- Weak Acid Example: Acetic acid (CH₃COOH) is a classic weak acid.
- Only some of it breaks down into H⁺ and CH₃COO⁻.
- Weak Base Example: Ammonia (NH₃) is the most common weak base.
- Reacts with water to form NH₄⁺ and OH⁻.
- **Key...

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