5.1.3 Buffers OCR A Level Chemistry H432

Unit outcomes: Understand (i) a buffer solution as a system that minimises pH changes on addition of small amounts of an acid or a base (j) formation of a buffer solution from: (i) a weak acid and a salt of the weak acid, e.g. CH3COOH/CH3COONa (ii) excess of a weak acid and a strong alkali, e.g. excess CH3COOH/NaOH (k) explanation of the role of the conjugate acid–base pair in an acid buffer solution, e.g. CH3COOH/CH3COO–, in the control of pH (l) calculation of the pH of a buffer solution, from the Ka value of a weak acid and the equilibrium concentrations of the conjugate acid–base pair; calculations of related quantities (m) explanation of the control of blood pH by the carbonic acid–hydrogencarbonate buffer system