Buffer Calculator
Buffer calculator
Compute buffer pH using Henderson-Hasselbalch.
InputsChemistry3 fieldsLive
Result
pH = 5.06103
Uses pH = pKa + log10([A-]/[HA]).
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Formula
pH = pKa + log10([A-]/[HA]) Symbol legend
| Symbol | Meaning | Unit | Copy |
|---|---|---|---|
\mathrm{p}K_a | Acid dissociation constant in p-scale | - | |
[A^-] | Conjugate base concentration | mol/L | |
[HA] | Weak acid concentration | mol/L |
- Enter pKa for the buffer system.
- Enter conjugate base and weak acid concentrations.
- Calculate pH from logarithm of their ratio.
Example
Worked example: acetate buffer
- 1 pKa = 4.76
- 2 [A-] = 0.20 M, [HA] = 0.10 M
- 3 pH = 4.76 + log10(0.20/0.10) = 5.06
Estimated buffer pH is about 5.06.
How
- Enter pKa for your acid system.
- Enter [A-] and [HA] concentrations.
- Read estimated buffer pH.
Avoid
- Swapping acid and base concentrations in the ratio.
- Using zero concentration for one buffer component.
- Applying the equation outside weak acid/base buffer conditions.
Ref only. Verify values. Follow lab safety.
FAQ
Is this exact for all buffers?
It is an approximation that works best for dilute weak acid/conjugate base systems.
What happens if conjugate-base concentration equals weak-acid concentration?
Then log10(1)=0 and pH equals pKa.
Can I use this for strong acids?
No, Henderson-Hasselbalch is intended for weak acid/base buffer systems.
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