Calculateur de pH Tampon Gratuit
Calculez le pH d'un tampon avec l'équation de Henderson-Hasselbalch.
Buffer pH
4.76
Buffer pH vs pKa of Weak Acid
Formule
## Henderson-Hasselbalch Equation ### Formula **pH = pKa + log₁₀([A⁻] / [HA])** Where: - **pH** = hydrogen ion activity - **pKa** = acid dissociation constant (log scale) - **[A⁻]** = concentration of conjugate base - **[HA]** = concentration of weak acid When [A⁻] = [HA], pH = pKa. Buffers resist pH changes best within ±1 of the pKa.
Exemple Résolu
An acetate buffer with pKa = 4.76, [CH₃COO⁻] = 0.1 M, [CH₃COOH] = 0.1 M.
- 01pH = pKa + log₁₀([A⁻]/[HA])
- 02pH = 4.76 + log₁₀(0.1/0.1)
- 03pH = 4.76 + log₁₀(1)
- 04pH = 4.76 + 0
- 05pH = 4.76
Questions Fréquentes
What is the Henderson-Hasselbalch equation?
It relates the pH of a buffer solution to the pKa of the acid and the ratio of conjugate base to acid concentrations. It is derived from the Ka expression by taking logarithms.
When is this equation most accurate?
It works best when the buffer ratio [A⁻]/[HA] is between 0.1 and 10, i.e., within ±1 pH unit of the pKa.
Can I use this for basic buffers?
Yes. Use pKa of the conjugate acid, [A⁻] as the base form, and [HA] as the acid form of the buffer pair.
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