Buffer solutionsEdexcel International A Level Chemistry: Flashcards
What these 13 flashcards ask
- What is a buffer solution?
- What does an acidic buffer contain?
- How does an ethanoic acid buffer remove added H⁺?
- How does it remove added OH⁻?
- Write the formula for [H⁺] in a buffer.
- What is the pH of a buffer with [HA] = [A⁻]?
- How do you find the ratio needed for a buffer of given pH?
- Why can amounts replace concentrations in buffer calculations?
- What is the half-neutralisation point?
- How is Ka found from a titration curve?
- Which buffer keeps blood at about pH 7.4?
- Why must the pH of blood stay constant?
- Why are buffers used in foods?
Exam questions on Buffer solutions
- A technician prepares solutions containing ethanoic acid and sodium ethanoate. The Ka of ethanoic acid is 1.74 × 10⁻⁵ mol dm⁻³, so its pKa is 4.76.Explain how a buffer made from ethanoic acid and sodium ethanoate resists a change in pH when a small amount of hydrochloric acid is added.2 marks
- Human blood is kept at a pH of about 7.4. This is maintained largely by a buffer system based on carbonic acid, H₂CO₃, and hydrogencarbonate ions, HCO₃⁻.Explain why it is important that the pH of blood remains almost constant, and how the buffer achieves this.2 marks
- A technician needs 500 cm³ of a buffer solution of pH 5.00. The final buffer must contain ethanoic acid at a concentration of 0.500 mol dm⁻³, and the conjugate base is supplied by solid sodium ethanoate, CH₃COONa (M = 82.0 g mol⁻¹). The Ka of ethanoic acid is 1.74 × 10⁻⁵ mol dm⁻³.Calculate the mass of sodium ethanoate needed.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).