Ka/Kb ⇄ pKa/pKb Converter

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Chemistry & Materials

Tranche

tranche-4

Evidence ID

t4-039

Ledger rows

1

No ledger note is attached.

Review findings

The core relationships are conditionally standard, but the instrument cannot be labeled an unqualified converter until it specifies base-10 logarithms, inverse formulas, conjugate-pair semantics, the Kw value or temperature input, and valid positive input constraints.

Formula and scope findings

• The p-value formula must explicitly use base-10 logarithms: pKa=-log10(Ka) and pKb=-log10(Kb); an unspecified log base is ambiguous.
• The inverse formulas are missing: Ka=10^(-pKa) and Kb=10^(-pKb).
• Ka·Kb=Kw is valid only for a conjugate acid/base pair using consistent activity conventions and the same temperature; it is not a general relation between arbitrary Ka and Kb values.
• The specification does not define the Kw value or temperature. At 25 °C, a common approximation is Kw=1.00×10^-14, but Kw varies with temperature and convention.

Unit assumptions

• Ka, Kb, and Kw are treated as dimensionless equilibrium constants based on activities; dimensional concentration-based constants cannot be used without a defined standard-state convention.
• The test vectors assume Kw=1.00×10^-14 at 25 °C.
• All Ka, Kb, pKa, and pKb values are positive-domain values except that p-values may be zero; logarithms are base 10.

Boundary hardening

Recorded hazards

• Ka=0 or Kb=0 causes division by zero when deriving the conjugate constant and makes the logarithm undefined.
• Negative Ka, Kb, or Kw values are invalid for these logarithms and equilibrium-constant calculations.
• The implementation must reject missing, nonnumeric, NaN, infinite, zero, or negative equilibrium constants when logarithms or reciprocal conversions are required.
• Using a default Kw without displaying or documenting its temperature can produce materially incorrect results.
• Inputs with concentration units are an ambiguity or unit-conversion trap unless the standard-state convention is explicitly defined.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "Ka": 0.00001
  },
  "expected_outputs": {
    "Ka": 0.00001,
    "pKa": 5,
    "Kb": 1e-9,
    "pKb": 9
  },
  "working": "1. pKa=-log10(1×10^-5)=5. 2. Kb=Kw/Ka=(1×10^-14)/(1×10^-5)=1×10^(-14+5)=1×10^-9. 3. pKb=-log10(1×10^-9)=9."
}

Related workflows

Sources and evidence

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

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche4/tranche4-results.json