Acid-Base Chemistry & pH

Proton transfer, titration curves, and buffer systems

Acids donate protons (H⁺); bases accept protons (Brønsted-Lowry definition). Strong acids (HCl, H₂SO₄, HNO₃) dissociate completely: [H⁺] = initial acid concentration. Weak acids partially dissociate; Ka = [H⁺][A⁻]/[HA]. pH = -log[H⁺]. At 25°C, Kw = [H⁺][OH⁻] = 10⁻¹⁴; neutral pH = 7. Titration: adding strong base to acid gradually neutralizes it. The equivalence point is where moles of base = moles of acid (pH = 7 for strong/strong, > 7 for weak acid/strong base). The buffer region (±1 unit from pKa) resists pH changes. Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA]). Maximum buffer capacity when [A⁻] = [HA] (pH = pKa).