Hess's Law Enthalpy 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

t8-013

Effect

Computation or source lookup only

Input and validation requirements

• Division by zero or singular-system hazards can occur if the reaction matrix is rank-deficient; the solver must report underdetermined or inconsistent inputs.
• A supplied reaction may be unbalanced in atoms or charge; this must be rejected before solving.
• Missing or inconsistent phase labels can silently produce an incorrect enthalpy.
• Mixing J, kJ, cal, kcal, or values reported per mole of different reference species can produce errors unless units and reaction extent are explicit.
• A zero or near-zero pivot requires numerical tolerance handling; exact rational stoichiometry is preferable where possible.
• The instrument should not claim a unique answer when multiple valid step combinations exist.
• Negative multipliers must be displayed clearly as reaction reversals, and fractional multipliers must be displayed without rounding that changes the target equation.

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": {
    "target_equation": "CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(l)",
    "known_reactions": [
      {
        "id": "R1",
        "equation": "C(graphite) + O2(g) -> CO2(g)",
        "delta_H": "-393.51 kJ"
      },
      {
        "id": "R2",
        "equation": "H2(g) + 1/2 O2(g) -> H2O(l)",
        "delta_H": "-285.83 kJ"
      },
      {
        "id": "R3",
        "equation": "CH4(g) -> C(graphite) + 2 H2(g)",
        "delta_H": "+74.85 kJ"
      }
    ]
  },
  "expected_outputs": {
    "overall_delta_H": "-890.32 kJ",
    "step_multipliers": {
      "R1": "1",
      "R2": "2",
      "R3": "1"
    },
    "oriented_steps": [
      "R1 as written",
      "2 × R2 as written",
      "R3 as written"
    ]
  },
  "reference_data": {
    "combined_equation": "R1 + 2R2 + R3 = CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(l)",
    "method": "Signed stoichiometric linear combination"
  },
  "working": "R1 + 2R2 + R3: C + O2 -> CO2; 2H2 + O2 -> 2H2O; CH4 -> C + 2H2. Cancel C and 2H2 from opposite sides. Remaining equation: CH4 + 2O2 -> CO2 + 2H2O. Arithmetic: ΔH = 1(-393.51) + 2(-285.83) + 1(+74.85) = -393.51 - 571.66 + 74.85 = -965.17 + 74.85 = -890.32 kJ."
}

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-tranche8/tranche8-results.json