{
  "capability_id": "chemistry.acid_base.ph",
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  "passed": 14,
  "failed": 0,
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    "boundary": {
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  "review_kind": null,
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  "reviewer_role": null,
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    "reviewer": null,
    "scope": [
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      "assumptions",
      "limitations",
      "sources",
      "tests"
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  "assumptions": [
    "pH = −log10[H+]",
    "pOH = −log10[OH−]",
    "Kw = 1e-14 at 25 °C",
    "Not Henderson–Hasselbalch",
    "Not ICE or activity coefficients"
  ],
  "limitations": [
    "Kw = 1e-14 at 25 °C (not temperature-dependent)",
    "Not Henderson–Hasselbalch buffer pH",
    "Not ICE, activity coefficients, or polyprotic"
  ],
  "boundary_conditions": [
    "ph_from_h missing h → MISSING_REQUIRED_INPUT",
    "h ≤ 0 or oh ≤ 0 → VALUE_MUST_BE_POSITIVE",
    "unknown mode → INVALID_MODE",
    "hh_ph is not a mode on this page"
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  "sources": [
    {
      "title": "OpenStax Chemistry 2e — pH and pOH",
      "section": "pH and pOH",
      "url": "https://openstax.org/books/chemistry-2e/pages/14-2-ph-and-poh",
      "supports": "pH = −log10[H3O+]; pOH = −log10[OH−]; pH + pOH = 14 at 25 °C",
      "kind": "reference"
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    {
      "title": "IUPAC Gold Book — pH",
      "section": "pH",
      "url": "https://goldbook.iupac.org/terms/view/P04524",
      "supports": "pH is defined from hydrogen-ion activity; dilute water uses −log10[H+]",
      "kind": "standard"
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        "h": 0.001
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        "pOH": 11,
        "model": "water_ion_product"
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        "pH": 3,
        "h": 0.001,
        "pOH": 11,
        "oh": 1e-11,
        "Kw": 1e-14,
        "pKw": 14,
        "T_C": 25,
        "model": "water_ion_product"
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      "tol": 1e-12
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      "ok": true,
      "kind": "boundary",
      "inputs": {
        "mode": "h_from_ph",
        "pH": 3
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      "expect": {
        "pH": 3
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      "expectWarning": null,
      "actual": {
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        "h": 0.001,
        "pOH": 11,
        "oh": 1e-11,
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        "pKw": 14,
        "T_C": 25,
        "model": "water_ion_product"
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      "tol": 1e-12
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      "kind": "boundary",
      "inputs": {
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        "oh": 0.001
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      "expect": {
        "pOH": 3,
        "pH": 11
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        "oh": 1e-11,
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        "pKw": 14,
        "T_C": 25,
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      "tol": 1e-12
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      "ok": true,
      "kind": "boundary",
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        "mode": "poh_from_ph",
        "pH": 3
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      "expect": {
        "pOH": 11
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      "expectWarning": null,
      "actual": {
        "mode": "poh_from_ph",
        "pH": 3,
        "h": 0.001,
        "pOH": 11,
        "oh": 1e-11,
        "Kw": 1e-14,
        "pKw": 14,
        "T_C": 25,
        "model": "water_ion_product"
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      "tol": 1e-12
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    {
      "id": "boundary-ph-zero",
      "ok": true,
      "kind": "boundary",
      "inputs": {
        "h": 0
      },
      "expectError": "VALUE_MUST_BE_POSITIVE",
      "code": "VALUE_MUST_BE_POSITIVE",
      "error": "h must be greater than zero"
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    {
      "id": "boundary-ph-missing",
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      "kind": "boundary",
      "inputs": {
        "mode": "ph_from_h"
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      "expectError": "MISSING_REQUIRED_INPUT",
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      "error": "h is required"
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      "inputs": {
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        "pKa": 5,
        "HA": 0.1,
        "A": 0.1
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      "code": "INVALID_MODE",
      "error": "mode must be ph_from_h|h_from_ph|poh_from_oh|oh_from_poh|ph_from_poh|poh_from_ph"
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