Equations · Chemistry and biology
Henderson–Hasselbalch equation
The pH of a buffer from the acid's pKa and the ratio of base to acid.
pH = pKa + log₁₀([A⁻] / [HA])
Aethel says
pH equals pKa plus log base 10 of the quantity the concentration of A minus, over the concentration of H A
What it says
A buffer holds a weak acid HA and its conjugate base A⁻. When they are present in equal amounts the log term is zero and the pH equals the pKa; each tenfold excess of base raises the pH by one.
Symbol by symbol
| Symbol | Say it | Means |
|---|---|---|
| pH | p H | minus the base-10 log of the hydrogen-ion concentration |
| pKa | p K a | minus the base-10 log of the acid dissociation constant |
| [A⁻] | the concentration of A minus | the concentration of the conjugate base |
| [HA] | the concentration of H A | the concentration of the acid |
More onlogLogarithm
Where you meet it
Chemistry, biochemistry and physiology.
Questions
How do you say Henderson–Hasselbalch equation out loud?
pH = pKa + log₁₀([A⁻] / [HA]) is read: “pH equals pKa plus log base 10 of the quantity the concentration of A minus, over the concentration of H A.” That is exactly what Aethel says when it meets the formula in a book.
What does pH mean in Henderson–Hasselbalch equation?
pH (said “p H”) is minus the base-10 log of the hydrogen-ion concentration.
What does pKa mean in Henderson–Hasselbalch equation?
pKa (said “p K a”) is minus the base-10 log of the acid dissociation constant.
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