A buffer solution consists of 6.00 g of ethanoic acid (CH₃COOH) and 12.3 g of sodium ethanoate (CH₃COONa) in 200 cm³ of aqueous solution.

(A_r values: H = 1.0, C = 12.0, O = 16.0, Na = 23.0; Ka for CH₃COOH = 1.74 × 10^–5 mol dm^–3)

a. What is the concentration of ethanoic acid in the buffer?

b. What is the concentration of sodium ethanoate in the buffer?

c. Calculate the pH of the buffer solution.

d. Using this solution as an example, explain why the pH of a buffer solution changes very little when small amounts of hydrogen ions or hydroxide ions are added to it.

e. Explain how the carbon dioxide/hydrogencarbonate buffer helps control blood pH.