A solution is prepared by dissolving 0.23 mol of butanoic acid and 0.27 mol of sodium butanoate in water sufficient to yield 1.00L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly. The pH does not decrease drastically because the HCl reacts with the present in the buffer solution. The Ka of butanoic acid is 1.36 x 10-3.