Strong and weak acid/base pH
Ideal strong/weak monoprotic acid or base with water ionization and charge balance.
- Runs in your browser
- No upload
- Check before download
Ideal strong/weak monoprotic acid or base with water ionization and charge balance. Supply Ka/Kb and Kw valid at your temperature. Temperature never adjusts them automatically; activities and polyprotic systems are excluded.
Model, grammar and limits
Kₐ=[H⁺][A⁻]/[HA]; Kᵦ=[BH⁺][OH⁻]/[B]; Kw=[H⁺][OH⁻]; Σzᵢcᵢ=0
Examples: H2O, K4[Fe(CN)6], CuSO4·5H2O; charges: Fe^2+, Cl^-, electron e^-. Element symbols are case-sensitive (118 symbols); a formula can have up to 256 characters, nesting up to 6, hydrate parts up to 8, subscripts up to 100000 and up to 1e9 atoms per element. Isotopes, leading formula coefficients and automatic reaction species are not supported.
Reactions: up to 12 species. ICE: up to 8 species, with coefficients from −12 to 12 and concentrations from 0 to 100 mol/L; K and Q from 1e−200 to 1e200. Aqueous temperature 273.15 to 373.15 K; Kw 1e−18 to 1e−10; Ka and Kb 1e−30 to 1e6; concentration up to 10 mol/L (titration and buffer parts up to 5). Titration: up to 1001 points; steps and end up to 100000 mL. Dilution: up to 100 stages, volumes up to 1e6 L. Nernst: n from 1 to 100, up to 12 activities, E° within ±100 V; gas inputs must be positive and up to 1e15, T up to 1e5 K. Numeric text up to 48 characters, no thousands separators.
Atom and charge coefficients and decimal dilution accounting are exact. Other results are numerical, shown with 10 significant digits, and the CSV has raw numeric values plus units. Roots take at most 180 iterations, and results whose residual can't be certified because resolution was lost are rejected. This is an educational model of your chosen setup, not a dosing or engineering instruction.
CIAAW abridged2024; CODATA2022 R=8.31446261815324 J/(mol K), F=96485.33212331002 C/mol
Runs in a local worker in your browser with a 15-second deadline; editing, resetting or canceling closes pending work. Inputs are never uploaded or saved automatically. Backup up to 1 MiB; original files stay unchanged. Input data, formulas and filenames are never sent. Only with your optional consent, Refentra sends aggregate counts of actions and outcomes, without input content.
Use this model
- Own inputs
Choose strong acid, strong base, weak acid or weak base. Enter the concentration in mol/L. Weak modes also need your Ka or Kb, plus your Kw and the temperature.
- Model, grammar and limits
A strong acid at 0.01 mol/L with Kw = 1e-14 at 25 °C gives approximately pH 2. The solver includes the water equilibrium instead of always using −log10(C).
- Download CSV report
Check the hydrogen, hydroxide and charge/mass residuals together with the pH. Keep the constants you supplied with the report. Changing the temperature does not update them automatically.
Questions and model limits
What does this result mean?
Ka and Kb describe weak dissociation, and Kw links hydrogen and hydroxide. Very dilute solutions need the water term, so the concentration alone is not enough.
How do I resolve rejected or missing input?
Use a positive Kw within 1e-18…1e-10, a concentration of 0…10 mol/L and a valid weak constant. Correct the units or rejected values before you run it again.
What are the limits of this tool?
An ideal monoprotic aqueous model. It has no activity corrections or mixtures and is not a lab measurement. The temperature must be 273.15…373.15 K, so supply constants that fit your case.