Reaction Stoichiometry / Limiting Reagent Solver mechanism

Model scope

The stated limiting-reagent method is chemically standard, but the specification needs an explicit input-unit schema, atomic-weight-table/version policy, parser grammar, validation rules, reaction-extent and excess formulas, and a clear definition of whether theoretical yield means moles, mass, or both. These unresolved ambiguities require review before implementation.

• The core method is standard only when the supplied equation is already correctly balanced: convert each reactant amount to moles, compute n_i/coefficient_i, and select the smallest value as the reaction extent.
• The specification does not explicitly state the reaction-extent formula or the excess formula: extent = min(n_i/a_i), reactant remaining = n_i - a_i*extent.
• The output 'theoretical yield' is ambiguous unless the product is identified and the product amount is reported both in moles and, when requested, mass using the product molar mass.
• Input validation constraints are missing: all supplied masses and moles should be nonnegative, stoichiometric coefficients should be positive, and at least one reactant and one product should be present.
• The equation parser and coefficient-balancer helper need defined syntax and validation for formulas, parentheses, charges, fractional coefficients, duplicate species, and already-balanced versus unbalanced equations.
• The atomic-weights table version and rounding policy are unspecified, so mass results may differ between implementations.

Units and conventions

• Mass inputs are in grams unless a row explicitly declares another mass unit; all masses must be converted to one consistent unit before division by molar mass.
• Molar masses use the same atomic-weight table as the displayed calculations; example values include H=1.008, O=16.00 or 16.015 as explicitly stated, N=14.01, Ca=40.08, C=12.01, Cl=35.45, Ag=107.87, and Na=22.99.
• Mole inputs are in mol and do not require conversion.
• Balanced coefficients are dimensionless mole ratios.
• Theoretical yield assumes pure reactants, complete conversion, no side reactions, and no experimental recovery or percent-yield factor.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "balanced_equation": "2 H2 + O2 -> 2 H2O",
    "reactants": {
      "H2": {
        "amount": 4.032,
        "unit": "g",
        "molar_mass_g_per_mol": 2.016
      },
      "O2": {
        "amount": 32,
        "unit": "g",
        "molar_mass_g_per_mol": 32
      }
    },
    "requested_products": [
      "H2O"
    ],
    "product_molar_masses_g_per_mol": {
      "H2O": 18.015
    }
  },
  "expected_outputs": {
    "limiting_reagent": "none; stoichiometric mixture",
    "reaction_extent_mol": 1,
    "products": {
      "H2O": {
        "amount_mol": 2,
        "theoretical_yield_g": 36.03
      }
    },
    "reactants_remaining": {
      "H2": {
        "amount_mol": 0,
        "mass_g": 0
      },
      "O2": {
        "amount_mol": 0,
        "mass_g": 0
      }
    }
  },
  "working": "n(H2) = 4.032 g / 2.016 g/mol = 2.000 mol. n(O2) = 32.00 g / 32.00 g/mol = 1.000 mol. Ratio for H2 = 2.000/2 = 1.000 mol reaction; ratio for O2 = 1.000/1 = 1.000 mol reaction. Both ratios are equal, so neither reagent is limiting. Extent = 1.000 mol. n(H2O) = 2*1.000 = 2.000 mol. Theoretical mass H2O = 2.000 mol * 18.015 g/mol = 36.030 g. H2 remaining = 2.000 - 2*1.000 = 0 mol; O2 remaining = 1.000 - 1*1.000 = 0 mol."
}

Failure boundary

• Division by zero occurs if a parsed stoichiometric coefficient is zero or if a molar mass is zero or missing.
• Negative masses or moles produce chemically invalid results unless rejected.
• If every reactant amount is zero, the limiting reagent is mathematically tied or undefined; the UI needs an explicit policy.
• Mass and mole units can be mixed incorrectly if each reactant row does not carry an explicit unit and conversion path.
• A product mass cannot be computed without a valid product formula and molar mass.
• Unbalanced equations, malformed formulas, unknown elements, and coefficients rounded during balancing can silently produce incorrect limiting-reagent and yield results.
• Real samples may contain impurities, hydrates, solutions with concentration/volume, or percent yield; treating entered sample mass as pure compound should be clearly labeled as an assumption.

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-tranche6/tranche6-results.json