Polyprotic Acid Speciation Calculator
Calculate ideal protonation-state fractions, concentrations and average formal charge for one- to four-step acids.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Use supplied pH and successive macroscopic dissociation constants to partition one analytical species family.
Relative species weights: 1,Ka1/H,Ka1Ka2/H²,…; normalize using log-sum-exp
Worked example
For a monoprotic neutral acid at pH=pKa, both state fractions are 0.5 and the average formal charge is −0.5.
Assumptions and input details
Ideal concentration fractions at externally supplied pH; this does not solve electroneutrality or buffer pH. pKa values must match temperature/ionic environment. No metal binding, complexes, activity corrections or real species identification.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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