The curve below shows the titration of a diprotic acid H₂A with NaOH. Estimate the pKa values for the diprotic acid.

• A. pKa₁ = 2.0; pKa₂ = 5.3
• B. pKa₁ = 4.2; pKa₂ = 9.4
• C. pKa₁ = 2.5; pKa₂ = 6.5
• D. pKa₁ = 3.5; pKa₂ = 7.0

Answer: (C)