Redox Half-Reaction Balancer

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Chemistry & Materials

Tranche

tranche-8

Evidence ID

t8-005

Ledger rows

1

No ledger note is attached.

Review findings

The core half-reaction rules and integer null-space approach are standard for single-step ionic redox balancing. The product contract and input contract need clarification for half-reaction-only inputs: the instrument should either return only the balanced supplied half-reaction or require a full redox pair before producing an overall equation and transferred-electron count. The basic-medium algorithm should explicitly specify equal OH^- addition to both sides followed by cancellation.

Formula and scope findings

• The listed half-reaction procedure is standard, but the basic-medium instruction is incomplete: a correctly balanced acidic form must be converted by adding equal OH- to both sides, then canceling H2O and any excess OH-; adding OH- without this constraint can produce incorrect results.
• For a full redox equation, the engine must identify oxidation and reduction halves and equalize electron counts before addition. The specification does not explicitly state this required step.
• The input contract is ambiguous: a single half-reaction cannot by itself determine a balanced overall equation or electrons transferred for the complete redox process, although those are listed as universal outputs.

Unit assumptions

• Chemical formulas and charges are interpreted literally; coefficients are dimensionless stoichiometric integers.
• H+, OH-, H2O, and e- are explicit balancing species, with acidic conditions permitting H+ and basic conditions permitting OH-.
• Electrons are counted as transferred per balanced overall reaction, with the oxidation and reduction electron counts equal after scaling.
• No physical units are applicable; concentrations, activities, temperature, and pressure are not part of this stoichiometric balancer.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The identical-species input Fe2+ -> Fe2+ forces an electron coefficient of exactly zero. Any implementation that normalizes by electrons transferred can divide by zero or produce an undefined result instead of rejecting the non-redox input. The slash-form convention probe also exposes a direction ambiguity that can reverse the reported half-reaction.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "equation": "MnO4^- + Fe^2+ -> Mn^2+ + Fe^3+",
    "medium": "acidic",
    "input_type": "full_redox"
  },
  "expected_outputs": {
    "balanced_half_reactions": [
      "MnO4^- + 8H^+ + 5e^- -> Mn^2+ + 4H2O",
      "Fe^2+ -> Fe^3+ + e^-"
    ],
    "balanced_overall_equation": "MnO4^- + 8H^+ + 5Fe^2+ -> Mn^2+ + 4H2O + 5Fe^3+",
    "electrons_transferred": 5,
    "residual": {
      "Mn": 0,
      "Fe": 0,
      "O": 0,
      "H": 0,
      "charge": 0
    }
  },
  "reference_data": {
    "standard_method": "acidic half-reaction method",
    "oxidation_half": "Fe^2+ -> Fe^3+ + e^-",
    "reduction_half": "MnO4^- + 8H^+ + 5e^- -> Mn^2+ + 4H2O"
  },
  "working": "Reduction half: Mn is already balanced. Put 4H2O on the product side to balance 4 O. Put 8H+ on the reactant side to balance 8 H. Charges are reactants -1 + 8 = +7 and products +2, so add 5e^- to the reactant side: +7 - 5 = +2. Oxidation half: Fe is balanced; charge changes from +2 to +3, so add 1e^- to products. Multiply the iron half by 5. Add: MnO4^- + 8H^+ + 5e^- + 5Fe^2+ -> Mn^2+ + 4H2O + 5Fe^3+ + 5e^-. Cancel 5e^- from both sides. Element arithmetic: Mn 1=1, Fe 5=5, O 4=4, H 8=8. Charge: left -1 + 8 + 10 = +17; right +2 + 15 = +17; residuals are all zero."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche8/tranche8-results.json
• BOUNDARY_HAZARD_CATALOG.json