Acid–base chemistry

Acid–base chemistry describes how acids donate protons and bases accept them, and how these transfers shape the acidity and basicity of chemical systems.

Brønsted–Lowry acid–base theory: A theory defining acids as proton donors and bases as proton acceptors. It supplies the proton-transfer definition used to describe most reactions in this field.
Chemical equilibrium: A state in which forward and reverse reaction rates are equal. Acid dissociation and proton transfer are governed by equilibrium constants.
Buffer solution: A solution that resists pH change through a weak acid–base pair. Buffers use conjugate partners to absorb added acid or base.
Arrhenius acid–base theory: A theory defining acids as substances that increase hydrogen-ion concentration in water and bases as substances that increase hydroxide-ion concentration. Its aqueous, ion-based definitions are narrower than proton-transfer theory.
Conjugate acid–base pair: Two species related by the gain or loss of a proton. Every Brønsted–Lowry proton transfer converts reactants into conjugate partners.
Autoionization of water: The transfer of a proton between two water molecules, producing hydronium and hydroxide. This equilibrium establishes water’s baseline ion concentrations and the pH scale.
Acid–base titration: A quantitative method that determines an analyte’s concentration by adding a reacting solution of known concentration. The titration curve reveals neutralization progress and equivalence points.
Solvent-system definition of acids and bases: A definition classifying acids and bases by their effects on a solvent’s characteristic cation and anion. It describes acid–base behavior through solvent ions rather than proton exchange.
Acid dissociation constant: An equilibrium constant measuring how extensively an acid donates protons in solution. Its value quantifies acid strength and predicts proton-transfer direction.
Hydronium ion: The H₃O⁺ ion formed when a water molecule accepts a proton. Hydronium represents solvated acidic protons in aqueous chemistry.

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