Buffer solutions

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  1. What is a buffer solution?
  2. Definition and uses.
  3. Adding acid to buffer solution: pH change
  4. Adding base to buffer solution: pH change
  5. Worked example of pH change to buffer.
  6. Buffers and change in concentration.
  7. The buffer region of a titration curve.
  1. Calculate the pH change that takes place when acid or base is added to buffer solutions.
    A 1L buffer solution is made from 0.4 mol ethanoic acid (CH3COOH) and 0.4 mol of its conjugate base, ethanoate (CH3COO-). The Ka of ethanoic acid is 1.4*10-5.
    What would be the pH change if 0.1 mol of H3O+ was added to this buffer?
    1. Show the effect of a buffer using a titration curve and find Ka of a weak acid in a buffer.
      Below is the titration curve of a weak acid by a strong base:
      1. At which point in the titration is a buffer effect occurring? Mark the region on the graph.
      2. pH1/2 during this titration was 3.82. Find the Ka of the weak acid in the buffer using the Henderson-Hasselbach equation.
        1. Calculate the concentration of solutions needed to prepare a buffer of a given pH.
          Ethanoic acid has a Ka of 1.4*10-5. What amounts are required to prepare a 100mL buffer with pH 4.25 using ethanoic acid, CH3COOH and sodium hydroxide, NaOH?

          1 Source for acidity constant (Ka) data: ATKINS, P. W., & DE PAULA, J. (2006). Atkins' Physical chemistry. Oxford, Oxford University Press.