1. The problem statement, all variables and given/known data How many moles of base would be needed to titrate one mole of this fully protonated peptide to a pH of 4.00? This polypeptide is V-A-Y-K-H. 2. Relevant equations Henderson-Hasselbalch: pH= pKa + log[A]/[HA] pKa of alpha COOH = 2.4 The alpha COOH (at the C-Terminus) is the only portion of the molecule that is deprotonated (basic) at pH 4.00, so we use its pKa for the calculation. 3. The attempt at a solution pH = pKa + log [A]/[HA] 4.0 = 2.4 + log [A]/[HA] 1.6= log [A]/[HA] 39.8 = A/HA I'm not sure how to go from the ratio of A/HA to the moles of base needed.