Acid–Base Theories
What You Will Learn: Acid–Base Theories · Brønsted–Lowry Acids and Bases · The pH Scale and Acid Strength
IB Chemistry topic guide
Reactivity 3: Mechanisms of Change
Reactivity 3: Mechanisms of Change is a core part of IB Chemistry. This guide connects the syllabus ideas behind Acid–Base Theories, pH Calculations and Buffers, Oxidation States and Redox, Electrochemical Cells, Substitution Reactions and 2 more units, shows how they appear in worked problems, and points you to the formulas and full lessons needed for exam revision.
What you will learn
Reactivity 3: Mechanisms of Change syllabus outline
The units below follow the structure used in the full Study to Learn course. Use the outline to identify exactly which idea needs attention, then work through the public example before continuing to the complete lesson path.
pH Calculations and Buffers
What You Will Learn: pH Calculations and Buffers · Weak Acids, Kₐ, and Buffer Solutions · Titration Curves and Indicators
Oxidation States and Redox
What You Will Learn: Oxidation States and Redox · Oxidation and Reduction · Balancing Redox Equations
Electrochemical Cells
What You Will Learn: Electrochemical Cells · Voltaic (Galvanic) Cells · Electrolytic Cells and Applications · The Nernst Equation and Concentration Effects (AHL)
Substitution Reactions
What You Will Learn: Substitution Reactions · Free Radical Substitution · Nucleophilic Substitution: Sₙ1 and Sₙ2
Addition Reactions
What You Will Learn: Addition Reactions · Electrophilic Addition to Alkenes · Addition Polymerisation and Markovnikov’s Rule
Electron-Pair Sharing Reactions
What You Will Learn: Electron-Pair Sharing Reactions · Condensation Polymerisation · Polymer Properties and Environmental Impact
Free worked preview
What You Will Learn: Acid–Base Theories
This complete preview comes from the Acid–Base Theories unit. It introduces the core language, shows the method in context, and gives you a real example of the lesson quality before you create an account.
What You Will Learn: Acid–Base Theories
Section F examines the mechanisms of chemical change, and this opening topic establishes acid–base chemistry rigorously rather than relying on everyday intuitions like "sour taste." The first lesson introduces the Brønsted–Lowry theory, defining acids as proton donors and bases as proton acceptors, and the conjugate acid–base pairs this creates. The second lesson builds the pH scale on top of that definition, showing how pH = −log[H⁺] relates hydrogen ion concentration to a measurable, logarithmic scale, and how strong and weak acids differ in the extent to which they dissociate.
What You'll Cover
- The Brønsted–Lowry theory of acids and bases as proton donors and acceptors, and conjugate acid–base pairs.
- The pH scale, its logarithmic relationship to [H⁺], and the distinction between strong and weak acids.
By the end of this topic you will have the theoretical and quantitative foundation for buffers and titrations covered next in F1.2.
Reviewed by the Study to Learn editorial team · Updated 2026-08-04