PH of acidic buffer = pKa + log [CH₃COONa - HCl] / [CH₃COOH + HCl] pKa of CH₃COOH = 4.74 Concentration of acetic acid in buffer = 2.0 M Concentration of sodium acetate = 1.0 M Concentration of HCl must add = x pH = 4.74 + log (1-x) / (2+x) = 4.11 x = concentration of HCl must be added = 0.43 M number of moles of HCl = M * V = 0.43 * 1 = 0.43 mol mass of HCl must be added = 0.43 * 36.5 = 15.7 g