Module 5 Acids, Bases, and Solubility Equilibrium
This lesson establishes the theoretical foundation of acid-base chemistry using the Brønsted-Lowry model. You'll learn to identify acids and bases by tracking proton (H⁺) transfer, recognize conjugate acid-base pairs, and understand why some species can act as both acids and bases. These fundamental concepts are essential before moving to pH calculations and equilibrium systems in the next lessons.
In this lesson, you'll master the following learning objective:
We begin with Brønsted-Lowry theory—the proton transfer model that explains most aqueous acid-base reactions. You'll learn to identify conjugate acid-base pairs, understand amphoteric substances like water, and work with the relationship between conjugate acid and base strengths.
Why This Matters: Understanding acid-base theories is the foundation for all subsequent work in this module. These concepts are essential for biochemical processes (enzyme function, protein structure), environmental science (acid rain, ocean chemistry), and pharmaceutical applications. Mastering conjugate pairs and proton transfer mechanisms prepares you for pH calculations, buffer systems, and titrations in later lessons.
How to Succeed: Watch the introductory video segments carefully, focus on identifying proton transfer in reactions, and practice recognizing conjugate acid-base pairs. Work through the interactive activities to reinforce pattern recognition.
Overby/Chang: Chemistry, 14th Ed. - Chapter 15: Complete Chapter (15.1-15.12)
Foundation Theory
The tabs to the left indicate you have two videos to watch.
Apply LO5.1.1: Use your understanding of Brønsted-Lowry acid-base theory from the videos above to identify conjugate acid-base pairs. Remember: a conjugate acid-base pair differs by exactly one proton (H⁺). Note: You'll practice Lewis acid-base pairs later in this lesson after learning Lewis theory.
Click to match each acid with its conjugate base. Each pair differs by exactly one H⁺ ion.
PROBLEM 1 - BASIC The concentration of H₃O⁺ ions in a lemon juice sample is 6.3 × 10⁻³ M at 25°C. Calculate the concentration of OH⁻ ions in this solution.
Given: [H₃O⁺] = 6.3 × 10⁻³ M, Temperature = 25°C, Kw = 1.0 × 10⁻¹⁴
Click to View Solution
Answer: [OH⁻] = 1.6 × 10⁻¹² M
Not what you got? Study this walk-through to understand the process.
Step 1: Identify the relationship we need to use: Kw = [H₃O⁺][OH⁻] = 1.0 × 10⁻¹⁴
Step 2: Rearrange to solve for [OH⁻]: [OH⁻] = Kw/[H₃O⁺]
Step 3: Substitute the known values: [OH⁻] = (1.0 × 10⁻¹⁴)/(6.3 × 10⁻³)
Step 4: Calculate: [OH⁻] = 1.6 × 10⁻¹² M
Step 5: Check reasonableness: Since [H₃O⁺] > [OH⁻], this confirms an acidic solution, which makes sense for lemon juice!
You now understand the theoretical foundation of acid-base chemistry through the Brønsted-Lowry model. You can identify acids, bases, and conjugate pairs by tracking proton transfer. This conceptual foundation prepares you for quantitative pH calculations in the next lesson.