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Henderson-Hasselbalch buffer calculator

A buffer sits at its pKa when acid and base are equal, and shifts by one pH unit for each factor of ten in the ratio.

mol/L
mol/L
Buffer pH
4.760
≈ Rounded Henderson-Hasselbalch
Base to acid ratio
1
Show the working
  1. pKa of the acid = 4.76
  2. Concentration of conjugate base = 0.1
  3. Concentration of the acid = 0.1
  4. Base to acid ratio = 0.1 / 0.1 = 1
  5. Buffer pH = 4.76 + log10(1) = 4.76

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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    The formula

    • pH = pKa + log10([A-] / [HA])

    The equation assumes the acid is weak and the ratio is between about 1:10 and 10:1; outside that range a buffer barely buffers.

    Acetic acid has a pKa of 4.76, which is the default here.

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