AP Chem Ch. 18: Principles of Reactivity: Reactions Between Acids & Bases

common ion effect
describes phenomenon in which titration is halted at some intermediate stage before the equivalence point & the ionization of the remaining lactic acid is affected by the lactate ion present - before the equivalence point, the weak acid is present along with some amount of its conjugate base; called this because an ion "common" to the ionization of the acid is present in an amount greater than that produced by simple acid ionization
buffer solution
in general, 2 species are required in a _____, one (an acid) capable of reacting w/ added OH⁻ ions & another (a base) that can consume added H₃O⁺ ions & the acid & base can't react w/ each other ∴ the _____ is usually prepared from roughly equal quantities of a conjugate acid-base pair: (a) a weak acid & its conjugate base (acetic acid & acetate ion, for example), or (b) a weak base & its conjugate acid (ammonia & ammonium ion, for example)
Henderson-Hasselbach equation
pH = pK(subscript a) + log [(conjugatebase)/(acid)]; shows clearly that the pH of the solution of a weak acid & its conjugate base is controlled primarily by the strength of the acid (as expressed by pK[subscript a])