Henderson–Hasselbalch Buffer Calculator 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

t4-051

Effect

Computation or source lookup only

Input and validation requirements

• log10([A−]/[HA]) is undefined for a zero or negative ratio; both concentrations must be strictly positive.
• Division by zero occurs if [HA] = 0.
• The inverse calculation can overflow or produce impractically large or small ratios for extreme target pH − pKa values.
• Using mismatched concentration units without conversion produces an incorrect ratio.
• The Henderson–Hasselbalch approximation can be inaccurate for concentrated, highly nonideal, very dilute, or strongly reacting solutions.
• A single known concentration is insufficient to determine both individual concentrations from only a target pH; an additional amount or concentration constraint is required.

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": {
    "pKa": 4.76,
    "A_minus_concentration_M": 0.1,
    "HA_concentration_M": 0.2
  },
  "expected_outputs": {
    "pH": 4.45897
  },
  "working": "[A−]/[HA] = 0.100 M / 0.200 M = 0.500. log10(0.500) = −0.30103. pH = 4.76 + (−0.30103) = 4.45897."
}

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-tranche4/tranche4-results.json