Percent Solution / Concentration-Unit Converter mechanism

Model scope

The specification needs explicit formulas and required inputs for every conversion path, especially %w/w↔%w/v↔%v/v, ppm/ppb, molarity↔molality, and mole fraction. The honest label should state that ppm↔molarity also requires solute molar mass and that density supplied alone does not resolve the distinction between mass-based and volume-based ppm conventions.

• The %w/v formula is correct only when solute mass is in grams and solution volume is in milliliters: (g/100 mL)×100 simplifies to g solute per 100 mL solution.
• ppm=mg/L is not a universal ppm definition; it is a dilute aqueous mass/volume approximation. ppm may instead mean mg/kg by mass, and the approximation requires an explicit density assumption.
• The molarity↔molality relationship is not specified. With density rho in g/mL, solute molar mass MW in g/mol, molarity C in mol/L, and molality b in mol/kg, the formulas are b=(1000C)/(1000rho−C×MW) and C=(1000rho×b)/(1000+b×MW).
• Conversions among %w/w, %w/v, and %v/v require additional quantities that are not listed, including solution density and, for %v/v conversions involving solute mass, solute density.
• Mole-fraction conversion requires the solvent identity or solvent molar mass and the relevant solute/solvent amounts; solute molar mass alone is insufficient.
• An atomic weights table is insufficient for arbitrary solute molar mass unless a molecular formula and a molecular-weight calculation are also supported.

Units and conventions

• %w/v uses grams of solute and milliliters of final solution.
• Molarity is mol solute per liter of final solution.
• Molality is mol solute per kilogram of solvent, not per kilogram of solution.
• The molarity↔molality formulas assume solution density is in g/mL and solute molar mass is in g/mol.
• The ppm and ppb test conversions use the dilute aqueous approximation: 1 ppm=1 mg/L and 1 ppb=1 microgram/L.
• For mole fraction in the applicable test vector, the solvent is water with molar mass 18.015 g/mol.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "solute_mass_g": 5,
    "solution_volume_mL": 100,
    "solute_molar_mass_g_per_mol": 58.44,
    "medium": "dilute aqueous"
  },
  "expected_outputs": {
    "percent_w_v": 5,
    "solute_mass_g_per_L": 50,
    "molarity_mol_per_L": 0.855578
  },
  "working": "%w/v=(5 g/100 mL)×100=5% w/v. 100 mL=0.100 L, so 5 g/0.100 L=50 g/L. Molarity=50 g/L ÷ 58.44 g/mol=0.855578 mol/L. Under the dilute-aqueous assumption, ppm=50 g/L×1000 mg/g=50000 mg/L=50000 ppm."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The specification exposes two concrete failure hazards: 100% w/w causes division by zero in molality, and several requested conversions, especially %v/v, are underdetermined without solute density. ppm-to-molarity also changes from an approximate dilute-aqueous branch to a density-corrected branch when density is supplied.

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-tranche3/tranche3-results.json
• BOUNDARY_HAZARD_CATALOG.json