Buffer Solution Calculation

• Buffer calculations
  
  
• Calculating the pH of a buffer - calculating amounts of salt and acid needed
  • Buffer calculation
    • A buffer solution was prepared which had a concentration of 0.20 mol dm^-3 in ethanoic acid and 0.10 mol dm^-3 in sodium ethanoate. If the K_a for ethanoic acid is 1.74 x 10^-5 mol dm^-3, calculate the theoretical hydrogen ion concentration and pH of the buffer solution.
    • K_a = [H⁺_(aq)] [salt_(aq)]_/[acid_(aq)]
    • 1.74 x 10^-5 = [H⁺_(aq)] x 0.10 / 0.20
    • [H⁺_(aq)] = 1.74 x 10^-5 x 0.20_/0.10 = 3.48 x 10^-5 mol dm^-3
    • pH = -log(3.48 x 10^-5) = 4.46