Titration Curve Simulator (weak acid/base biochem context) implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t6-089

Effect

Computation or source lookup only

Input and validation requirements

The idealized formula set is not fully defined at the zero-titrant boundary, invalid negative-volume inputs produce logarithm and zero-volume failures, and unspecified volume units can change the computed pH from 4.76 to approximately 12.998.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "analyte": "0.100000 mol/L HA",
    "initial_volume": "50.0000 mL",
    "pKa": 4.75,
    "titrant": "0.100000 mol/L NaOH",
    "titrant_volume": "0.00000 mL",
    "temperature": "25 °C",
    "model": "exact weak-acid initial equilibrium"
  },
  "expected_outputs": {
    "sampled_point": {
      "titrant_volume_mL": 0,
      "pH": 2.8779
    },
    "key_curve_features": {
      "equivalence_point_mL": 50,
      "half_equivalence_point_mL": 25,
      "half_equivalence_pH": 4.75,
      "buffering_region_approximately_mL": "4.54545 to 45.4545",
      "pH_as_titrant_volume_increases": "approaches 14 from below after excess strong base dominates"
    }
  },
  "working": "Ka = 10^(-4.75) = 1.77827941e-5. For HA ⇌ H+ + A-, let x = [H+]. The exact weak-acid equation is x^2 + Ka*x - Ka*C = 0. Thus x = (-Ka + sqrt(Ka^2 + 4*Ka*C))/2 = (-1.77827941e-5 + sqrt((1.77827941e-5)^2 + 4*(1.77827941e-5)*(0.100000)))/2 = 0.00132466 mol/L. Therefore pH = -log10(0.00132466) = 2.87790."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche6/tranche6-results.json