Source: https://guthlabs.ai/docs/instruments/reaction-stoichiometry-limiting-reagent-solver/mechanism/

instrument mechanism / verified-clean

# Reaction Stoichiometry / Limiting Reagent Solver mechanism

The inspectable method record for Reaction Stoichiometry / Limiting Reagent Solver, kept separate from implementation and qualification.

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

## 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

[01**Overview**](<https://guthlabs.ai/docs/instruments/reaction-stoichiometry-limiting-reagent-solver/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/reaction-stoichiometry-limiting-reagent-solver/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/reaction-stoichiometry-limiting-reagent-solver/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`