Source: https://guthlabs.ai/docs/instruments/molar-mass-formula-mass-calculator/mechanism/

instrument mechanism / verified-with-binding-errata

# Molar Mass / Formula Mass Calculator mechanism

The inspectable method record for Molar Mass / Formula Mass Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **verified-with-binding-errata**

## Model scope

The arithmetic algorithm is correct for the stated scope, and the four vectors cover a simple formula, a hydrate, nested parentheses, and a single-element boundary case. The verdict is NEEDS_REVIEW because the atomic-weight data source, precision/rounding policy, and exact accepted formula grammar are not specified, while the phrase 'any chemical formula string' overclaims the documented parser scope.

- The core formula M = Σ(nᵢ·Aᵢ) is the standard molar-mass method and is correct for neutral formulas with integer atom counts.

- The claim 'any chemical formula string' is too broad unless the grammar explicitly defines support for ionic charges, isotope notation, bracketed coordination complexes, fractional stoichiometric coefficients, leading coefficients, dot/middle-dot hydrate notation, and phase labels.

- 'IUPAC 2021 standard atomic weights / CODATA' is ambiguous: standard atomic weights and CODATA fundamental constants are different data sources. The instrument must identify one atomic-weight table, its revision, and its rounding policy.

- The specification does not state whether output is rounded, and to how many decimal places or significant figures. Different atomic-weight precision and rounding choices can change displayed totals.

- The parser must distinguish a hydrate separator such as '·' from unsupported punctuation and must define whether whitespace around the separator is allowed.

## Units and conventions

- Atomic weights Aᵢ are conventional relative atomic masses expressed numerically in unified atomic mass units per atom; the numerical molar-mass value is used in g/mol because 1 u per particle corresponds numerically to 1 g/mol.

- The test vectors use these conventional atomic weights in g/mol: H=1.008, O=15.999, Cu=63.546, S=32.06, Al=26.9815385, N=14.007, Ca=40.078.

- Outputs are total molar mass in g/mol and per-element contributions in g/mol.

- The formula represents one mole of formula units and contains integer, nonnegative atom counts.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "formula": "H2O",
    "atomic_weights": {
      "H": 1.008,
      "O": 15.999
    }
  },
  "expected_outputs": {
    "molar_mass_g_per_mol": 18.015,
    "element_mass_breakdown_g_per_mol": {
      "H": 2.016,
      "O": 15.999
    }
  },
  "working": "Parse counts: H₂O gives n(H)=2 and n(O)=1. H contribution = 2 × 1.008 = 2.016 g/mol. O contribution = 1 × 15.999 = 15.999 g/mol. Total = 2.016 + 15.999 = 18.015 g/mol."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The extreme-count vector exposes a precision-loss break if the parser accepts subscripts above JavaScript's safe-integer limit instead of rejecting them. The convention probe also exposes a severe interpretation hazard if element-symbol capitalization is not enforced.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/molar-mass-formula-mass-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/molar-mass-formula-mass-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/molar-mass-formula-mass-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-tranche6/tranche6-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`