Buffer solutionsEdexcel A-Level Chemistry: Mind map

Exam questions on Buffer solutions

1. A food scientist wants to keep the pH of a sauce steady during storage. She uses a mixture of ethanoic acid, CH₃COOH, and sodium ethanoate, CH₃COONa, in water. For ethanoic acid, $K_a$ = 1.74 × 10⁻⁵ mol dm⁻³ at 298 K.
   Explain how this mixture resists a change in pH when a small amount of hydrochloric acid is added.2 marks
2. A technician prepares a buffer solution by dissolving sodium ethanoate in ethanoic acid. The final solution contains ethanoic acid at 0.250 mol dm⁻³ and sodium ethanoate at 0.150 mol dm⁻³. For ethanoic acid, $K_a$ = 1.74 × 10⁻⁵ mol dm⁻³ at 298 K.
   Calculate the pH of the buffer solution.2 marks
3. A student prepares 100 cm³ of a buffer solution containing 0.0500 mol of ethanoic acid and 0.0500 mol of sodium ethanoate at 298 K. For ethanoic acid, $K_a$ = 1.74 × 10⁻⁵ mol dm⁻³. She then adds 0.00500 mol of solid sodium hydroxide. Assume that adding the solid does not change the volume.
   Calculate the pH of the solution after the sodium hydroxide has been added.3 marks