General Chemistry: Acids, Bases & Solutions
Free MCAT study guide — Chemical and Physical Foundations of Biological Systems
Acid-Base Chemistry
| Definition | Acid | Base |
|---|---|---|
| Arrhenius | Produces H⁺ in water | Produces OH⁻ in water |
| Brønsted-Lowry | Proton (H⁺) donor | Proton (H⁺) acceptor |
| Lewis | Electron pair acceptor | Electron pair donor |
pH = −log[H⁺] | pOH = −log[OH⁻] | pH + pOH = 14
Ka × Kb = Kw = 1.0 × 10⁻¹⁴ | pKa + pKb = 14
Buffers
Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA])
Key Point: Buffers work best within ±1 pH unit of pKa. Maximum capacity when [HA] = [A⁻].
Solutions
Colligative Properties
Depend on number of solute particles, not identity:
| Property | Equation | Effect of solute |
|---|---|---|
| Boiling point elevation | ΔTb = iKbm | BP increases |
| Freezing point depression | ΔTf = iKfm | FP decreases |
| Osmotic pressure | Π = iMRT | Creates osmotic pressure |
| Vapor pressure lowering | P = χ_solvent × P° | VP decreases (Raoult's law) |
Key Point: van't Hoff factor (i): NaCl → i ≈ 2, CaCl₂ → i ≈ 3, glucose → i = 1
Electrochemistry
E°cell = E°cathode − E°anode | ΔG° = −nFE°
Key Point: AN OX, RED CAT. Anode = oxidation (−), Cathode = reduction (+) in galvanic cells.
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