A 500 mg dietary supplement of L-lysine (an amino acid, 146.2 g/mol) required 68.4 mL of 0.100 M NaOH to reach the end point. How many protons were removed for each L-lysine molecule in this titration?

Question

Quizplus · Accepted Answer

In the titration, NaOH is the titrant and L-lysine is the analyte. The balanced chemical equation between NaOH and L-lysine is:

NaOH + H₂N(CH₂)₄CH(NH₂)COOH → H₂O + Na⁺ + H₂N(CH₂)₄CH(Na)COO⁻

From this equation, we can see that each L-lysine molecule has two acidic protons that can react with NaOH. Therefore, 68.4 mL of 0.100 M NaOH is enough to remove two protons from each L-lysine molecule. Hence, the answer is (B) 2.

A 500 Mg Dietary Supplement of L-Lysine (An Amino Acid