Acid dissociation constant Ka
Acid dissociation constant Ka
Formula
pKa = −log₁₀Ka
Real World
Aspirin (acetylsalicylic acid, pKa ≈ 3.5) is a stronger weak acid than ethanoic acid (pKa ≈ 4.8), which is why pharmaceutical companies formulate aspirin with buffering agents to reduce stomach irritation.
Exam Focus
When calculating [H⁺] from Ka, assume [H⁺] = [A⁻] and that dissociation is negligible compared to initial concentration.
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