Propanoic acid (C2H5COOH\text{C}_2\text{H}_5\text{COOH}C2H5COOH) is a weak acid.
The acid dissociation constant (KaK_aKa) for propanoic acid is 1.35 × 10-5 mol dm-3 at 25 ∘C25\text{ }^\circ\text{C}25 ∘C.
State the meaning of the term weak acid.
Give an expression for the acid dissociation constant for propanoic acid.
A student dilutes 15.0 cm3 of 0.600 mol dm-3 propanoic acid by adding water until the total volume is 250.0 cm3.
Calculate the pH of this diluted solution of propanoic acid.
Give your answer to 2 decimal places.
A buffer solution with a pH of 4.85 is made by dissolving x gx\text{ g}x g of sodium propanoate (C2H5COONa\text{C}_2\text{H}_5\text{COONa}C2H5COONa) in a solution of propanoic acid. The final volume of buffer solution is 500 cm3 and the final concentration of the propanoic acid is 0.120 mol dm-3.
Calculate x x\,x in g\text{g}g.
77 exam-style questions on AQA A Level Chemistry Acids and bases (A-level only), covering Brønsted–Lowry acid–base equilibria in aqueous solution (A-level only), Definition and determination of pH (A-level only), The ionic product of water, $K_w$ (A-level only), Weak acids and bases $K_a$ for weak acids (A-level only), pH curves, titrations and indicators (A-level only), and Buffer action (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.