Percent Composition Calculator mechanism

Model scope

The core mass-percent equation is correct under the stated unit and parsing assumptions. Verdict is NEEDS_REVIEW because the exact ambiguity is unspecified formula-language support and the undefined meanings of n, Aᵢ, M, atomic-weight standard, and rounding policy.

• The formula %element=(n·Aᵢ/M)×100 is standard only when n is the integer count of the element in one formula unit and M is explicitly defined as Σ(nⱼ·Aⱼ), the formula-unit molar mass.
• The specification does not define how chemical formula notation is parsed, including parentheses, nested groups, hydrates, dot notation, charges, isotope labels, or fractional stoichiometry.
• The atomic-weights table is unspecified; results depend on the selected standard atomic weights and rounding policy.
• The pie breakdown has no separate mathematical formula stated; it should use the same normalized per-element percentages and therefore sum to 100% within rounding tolerance.

Units and conventions

• Aᵢ is the atomic weight in g/mol, or any consistent mass-per-mole unit; M is in the same mass-per-mole unit, so the units cancel.
• n is dimensionless and represents the number of atoms of element i in one formula unit.
• Percentages are mass percentages, not mole percentages or volume percentages.
• The test calculations use these atomic weights: H=1.008, O=15.999, C=12.011, Na=22.990, Cl=35.45, Cu=63.546, S=32.06.
• For CuSO4·5H2O, the hydrate dot is assumed to mean CuSO4 plus five H2O units, with the resulting composition Cu1S1O9H10.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "formula": "H2O",
    "atomic_weights": {
      "H": 1.008,
      "O": 15.999
    }
  },
  "expected_outputs": {
    "per_element_percent": {
      "H": 11.190674,
      "O": 88.809326
    },
    "total_percent": 100
  },
  "working": "M = (2×1.008) + (1×15.999) = 2.016 + 15.999 = 18.015 g/mol. H% = (2×1.008 ÷ 18.015)×100 = (2.016 ÷ 18.015)×100 = 11.190674%. O% = (1×15.999 ÷ 18.015)×100 = 88.809326%. Check: 11.190674 + 88.809326 = 100.000000%."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The zero-count input H0 produces an undefined 0/0 calculation unless explicitly rejected. Parenthesis handling and hydrate-dot interpretation also create materially different results if parser conventions are not enforced.

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-tranche2/tranche2-results.json
• BOUNDARY_HAZARD_CATALOG.json