Verified calculation capability

pH Calculation Capability

Water-ion pH and pOH identities at 25 °C: pH = −log10[H+], pOH = −log10[OH−], pH + pOH = 14. Not Henderson–Hasselbalch and not ICE. · Chemistry · Acid Base

Capability ID chemistry.acid_base.ph · version 1.0.0

Open calculator REST API MCP Evidence Evidence JSON Review policy

Model

pH: pH = −log₁₀[H⁺]
Water ion product: pH + pOH = 14

Solve modes: ph from h · h from ph · poh from oh · oh from poh · ph from poh · poh from ph

Inputs / Outputs

Canonical symbols for this capability. Agent schemas remain the contract.

Symbol	Quantity	Unit	Role
`h`	[H+] in mol/L. Required for ph_from_h. REST/MCP alias. Share uses h_mol_L.	—	input / output
`pH`	pH. Required for h_from_ph and poh_from_ph.	—	input / output
`oh`	[OH−] in mol/L. Required for poh_from_oh. Share uses oh_mol_L.	—	input / output
`pOH`	pOH. Required for oh_from_poh and ph_from_poh.	—	input / output
`Kw`	—	—	output
`pKw`	—	—	output
`T`	temperature	°C	output
`model`	—	—	output

Assumptions / Validity

Declared scope for this capability. Do not use it outside this domain.

Assumptions

pH = −log10[H+]
pOH = −log10[OH−]
Kw = 1e-14 at 25 °C
Not Henderson–Hasselbalch
Not ICE or activity coefficients

Not supported

Henderson–Hasselbalch
ICE tables
activity coefficients
polyprotic
temperature-dependent Kw

Example

One numerical check. The calculator page holds worked steps and FAQ.

h=1e-3 → pH=3

Open this example in the calculator

Trust

Review-policy: engine tested — automated tests, sources, version lock, and evidence published. Supplemental to CVP; not Domain Expert Review. See CVP and Review policy.

Tier: Engine tested — catalog token engine_tested
Calculation version: 1.0.0
Evidence tests: 14/14 calculation tests · golden 1/1 · boundary 7/7 · property 6/6
Engine tested: Yes
Source checked: Yes
Supplemental domain review: Not performed
Named expert review: Not performed
Version lock: Supported (409 VERSION_MISMATCH)
Artifact consistency: Build verified · 1.0.0 (workspace artifacts agree)

Production attestation: Embedded snapshot: unpublished · Build schema 1.0.0 ready · Semantic contract ✓ · Attestation report not published on origin · Live production status PASS (0 stale; 164 CURRENT) @ 2026-09-16T06:44:24.909Z
Semantic contract: PASS
Evidence attested at: 2026-09-16T06:44:24.203Z
Last production check: 2026-09-16T06:44:24.203Z
Public / cache: —
Origin: —

Call this capability

Human page, REST, and MCP share the same engine and calculation_version. Build verified hashes workspace artifacts only. After deploy, attest:production GETs canonical URLs twice — the public/cached view an Agent actually hits, and origin — including every /capabilities/{id} HTML page. Public Capability HTML version must match catalog before production attestation passes. Live Trust rows above fetch /.well-known/calculatorx-production-attestation.json and the output schema const. Build hashes: release integrity. That proves currently published page / engine / schema / evidence / MCP agree — not that a historical version is independently immutable. Reference Calculation Standard — Production surface contract 3/3.

Tool id: ph
Engine: ph
REST: POST /api/v1/calc/ph
MCP: execute_calculation with capability_id: "chemistry.acid_base.ph"
Agent input schema: Canonical (MCP / Agent)
Output schema: JSON Schema (latest)
Versioned input schema: Immutable pin (1.0.0)
Versioned output schema: Immutable pin (1.0.0)

References

Human-readable sources plus CVP reference evidence classes.

Sources

Try with an agent

Inspect this capability via same-origin MCP, then call execute_calculation.

curl -sS -X POST 'https://www.calculatorx.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/call' \
  -H 'Mcp-Name: inspect_capability' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"inspect_capability","arguments":{"capability_id":"chemistry.acid_base.ph"}}}'

Inspect the trust tier and required assurance level before execution. Pin calculation_version (1.0.0) when reproducibility matters. Full protocol notes: MCP docs.