Source: https://guthlabs.ai/docs/instruments/standard-entropy-of-reaction-calculator/mechanism/

instrument mechanism / verified-clean

# Standard Entropy of Reaction Calculator mechanism

The inspectable method record for Standard Entropy of Reaction Calculator, kept separate from implementation and qualification.

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

## Model scope

The summation formula is correct: ΔS°rxn = ΣνiS°i(products) − ΣνiS°i(reactants). Verdict is NEEDS_REVIEW because the specification does not define the temperature, standard-state pressure, or required phase/state metadata. The claim should not imply a uniquely determined value until those conditions are explicit. The declared data source is also not implemented because already_built is false.

No additional formula finding is recorded.

## Units and conventions

- S° values must all use the same temperature, normally 298.15 K unless another temperature is explicitly selected.

- All S° values must be standard molar entropies in the same units; the reported output is J·mol⁻¹·K⁻¹ per mole of reaction as written.

- Stoichiometric coefficients are dimensionless, and fractional coefficients are permitted for a balanced equation.

- Standard states and phases must be specified consistently, typically 1 bar with explicit phases such as (s), (l), (g), or (aq).

- If input entropies are supplied in kJ·mol⁻¹·K⁻¹, they must be converted to J·mol⁻¹·K⁻¹ before reporting the output.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "balanced_equation": "CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(l)",
    "S_standard": {
      "CH4(g)": 186.3,
      "O2(g)": 205,
      "CO2(g)": 213.7,
      "H2O(l)": 69.9
    },
    "S_unit": "J mol^-1 K^-1",
    "temperature_K": 298.15
  },
  "expected_outputs": {
    "delta_S_rxn": -242.8,
    "unit": "J mol^-1 K^-1"
  },
  "working": "Products = (1 × 213.7) + (2 × 69.9) = 213.7 + 139.8 = 353.5 J mol^-1 K^-1. Reactants = (1 × 186.3) + (2 × 205.0) = 186.3 + 410.0 = 596.3 J mol^-1 K^-1. ΔS°rxn = 353.5 − 596.3 = −242.8 J mol^-1 K^-1."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The extreme-magnitude vector produces Infinity in IEEE-754 JavaScript arithmetic because the product entropy sum overflows; the calculator should reject non-finite inputs or outputs. The specification also contains no genuine multi-regime formula branch, so the branch test is necessarily a zero-crossing probe.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/standard-entropy-of-reaction-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/standard-entropy-of-reaction-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/standard-entropy-of-reaction-calculator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`