Source: https://guthlabs.ai/docs/instruments/ph-poh-calculator/

instrument / verified-clean

# pH / pOH Calculator

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

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/ph-poh-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/ph-poh-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/ph-poh-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/ph-poh-calculator/qualification/>)

## Ledger state

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

**Area**: Chemistry & Materials

**Tranche**: tranche-6

**Evidence ID**: t6-038

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The core arithmetic is correct for ideal dilute aqueous solutions at approximately 25 °C with concentrations expressed in mol/L. NEEDS_REVIEW is required because the specification leaves concentration units and the concentration-versus-activity convention implicit, and the fixed pH+pOH=14 relationship is temperature-dependent. The honest label appropriately mentions the 25 °C assumption but should also explicitly state the mol/L and ideal-solution assumptions.

### Formula and scope findings

- The formulas are standard under the stated 25 °C approximation, but pH and pOH are rigorously defined from activities rather than raw concentrations; using [H+] and [OH-] requires an ideal-dilute-solution assumption.

- pH+pOH=14 is valid only when pKw=14.000, approximately at 25 °C under the selected activity/concentration convention. It is not generally valid at other temperatures.

- The specification does not state the required units for [H+] and [OH-]. They must be supplied consistently, conventionally in mol/L, or the logarithms and Kw calculation are ambiguous.

### Unit assumptions

- [H+] and [OH-] are aqueous concentrations in mol/L (M), not mmol/L or mol/m³.

- Kw=1.0×10^-14 has units of (mol/L)^2 under the concentration approximation.

- All calculations use base-10 logarithms.

- The solution is sufficiently dilute that activities can be approximated by concentrations.

- The default temperature is 25 °C; for other temperatures, a supplied Kw(T) must replace 1.0×10^-14 and pH+pOH=14 must be replaced by pH+pOH=pKw(T).

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The specification does not define validation or rejection behavior for zero or negative concentrations, although these inputs cause division by zero or logarithms outside the real domain. It also leaves concentration units implicit, allowing a 3-pH-unit discrepancy for the same displayed numeric input.

## 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": {
    "pH": "0.00"
  },
  "expected_outputs": {
    "pOH": "14.000000",
    "[H+]_mol_per_L": "1.000000×10^0",
    "[OH-]_mol_per_L": "1.000000×10^-14"
  },
  "working": "pOH = 14.000000 - pH = 14.000000 - 0.000000 = 14.000000.\n[H+] = 10^(-pH) = 10^0 = 1.000000 mol/L.\n[OH-] = Kw/[H+] = (1.000000×10^-14)/(1.000000) = 1.000000×10^-14 mol/L.\nThis is a boundary-like case: pH=0 is valid mathematically, but represents an idealized 1 mol/L hydrogen-ion concentration."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## 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-tranche6/tranche6-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`