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cookiebookie
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Homework Statement
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.
Homework 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.
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.