About this site
This site explains acids, bases and pH with figures you can operate, and with an equilibrium engine that solves the full charge balance instead of the textbook shortcuts. It is free, has no ads and needs no sign-up.
How the figures compute§
Every pH on the site comes from one small, tested program. It writes down what must be true at equilibrium (each acid’s dissociation constants, the ion product of water, conservation of mass and the balance of positive and negative charge) and solves for the hydrogen-ion concentration numerically. Titration curves use the same balance, or Robert de Levie’s explicit form of it. No figure interpolates between textbook formulas, and where a figure shows a textbook shortcut it labels it and shows how far it is from the exact answer.
The constants are from reference sources: every pKa is the value selected by Goldberg, Kishore and Lennen (NIST, 2002), and the ion product of water at each temperature comes from the IAPWS formulation as tabulated by Arcis and Harvey for the CRC Handbook. Measured pH values of foods, rain, blood and seawater come from the FDA, the EPA, NOAA and the clinical and research literature, and are labelled as measurements. Values computed by the engine are labelled as computed.
What is simplified§
The engine treats activities as concentrations, which is accurate for dilute solutions and increasingly wrong for concentrated or salty ones. It works at 25 °C except where temperature is the subject. Each figure says what it idealizes next to it, and the sources page collects every such note.
How the science is checked§
The engine is tested twice: by its author against worked examples (including the titration tables in Harvey’s Analytical Chemistry 2.1) and invariants, and by an independent test suite written from the published equations and reference values, without reading the engine’s code. Every factual claim is recorded in a claims register with its source and checked by a reviewer who did not write it.
Found an error?§
Please open an issue on the source repository. Corrections are welcome and are credited.
Reuse§
Text and figures are licensed CC BY 4.0; code is MIT. Teachers may use and adapt any of it, with attribution.