Free Conjugate Acid-Base Calculator
Calculate the Ka of a conjugate acid from the Kb of its base (or vice versa) using the ion product of water Kw = Ka × Kb.
Conjugate K Value
0.0000
pK of Known4.74
pK of Conjugate9.26
Conjugate Acid-Base Relationship
Formula
Ka × Kb = Kw
Therefore:
At 25°C, Kw = 1.0 × 10⁻¹⁴. This means pKa + pKb = 14.
Example Calculation
Ammonia has Kb = 1.8 × 10⁻⁵. Find Ka of its conjugate acid NH₄⁺.
- 01Ka = Kw / Kb
- 02Ka = 1.0 × 10⁻¹⁴ / 1.8 × 10⁻⁵
- 03Ka = 5.56 × 10⁻¹⁰
- 04pKa = -log₁₀(5.56 × 10⁻¹⁰) = 9.26
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