Watch the pH jump at equivalence.
Titration curves, ideal gas isotherms and dilutions, each with physically bounded inputs and a live marker for the current state.
Strong acid / strong base
- Live
- pH
- 1.477
- pOH
- 12.523
- Equivalence
- 25 mL
- Total volume
- 37.5 mL
Before equivalence: excess H3O+ from the analyte controls pH.
What the model includes
Titration: strong monoprotic acid (HCl) with strong base (NaOH), both fully dissociated, at 25 C with Kw = 1.0 x 10^-14. pH comes from the charge balance [H+] - [OH-] = D, solved exactly, so water's own ions are included and the equivalence point is exactly pH 7.00. Volumes are assumed additive; activity effects are ignored.
Gas law: ideal gas, R = 8.314 L kPa/(mol K), absolute temperature in kelvin.
Dilution: moles of solute are conserved, and the final volume must be at least the stock volume.
25 mL of 0.100 M HCl + 0.100 M NaOH
Equivalence: V = (0.100 x 25.0) / 0.100 = 25.0 mL.
After 12.5 mL: excess H+ = 2.50 - 1.25 = 1.25 mmol in 37.5 mL = 0.0333 M, so pH = 1.48.
After 30.0 mL: excess OH- = 0.50 mmol in 55.0 mL = 0.00909 M, pOH = 2.04, pH = 11.96.