Unit 13
Acids and bases
From stomach acid to blood, pH governs chemistry and life. Starting from proton transfer, this unit uses exact equilibrium calculations to explain strong and weak acids, polyprotic speciation, buffers, and titration curves — and ends with you measuring an unknown concentration on the virtual bench.
- 1 Proton transfer: acids, bases and pH Acids donate protons, bases accept them — and water quietly does both. The logarithmic pH scale fits fourteen orders of magnitude onto one ruler. 25 min
- 2 Weak acids and bases: partial ionization At the same 0.1 M, acetic acid has one seventy-fifth of the [H₃O⁺] of hydrochloric acid. Ka tells you how much ionizes — and why dilution makes a weak acid ionize more. 25 min
- 3 Polyprotic acids and speciation Phosphoric acid, carbonic acid, and amino acids take different forms at different pH. Speciation diagrams show exactly who is present in blood, seawater, and cells. 25 min
- 4 Buffers: resisting pH change One drop of hydrochloric acid drops pure water from pH 7 to 3 but barely moves a buffer. See how a conjugate pair soaks up added acid and base, and design a buffer for a target pH. 25 min
- 5 Titration curves and indicators Strong acids, weak acids, weak bases, and polyprotic acids each leave a fingerprint on the titration curve. Learn to read the jump, the half-equivalence point, and the equivalence point — and to pick the right indicator. 30 min
- 6 What makes an acid strong Why is HI stronger than HF, HClO₄ stronger than HOCl, and an Fe³⁺ solution acidic? Bond energy, electronegativity, and charge delocalisation turn dozens of pKa values into a few rules. 20 min