Standard Reduction Potential / Activity Series Lookup mechanism

Model scope

The core ranking rule is chemically standard, but the specification is incomplete for an instrument that claims reaction prediction and spontaneity analysis. Define the exact lookup dataset and standard-state metadata, expose E°cell and its sign criterion, and state that predictions are thermodynamic standard-state predictions rather than unconditional kinetic reactivity claims.

• The comparison rule is correct for standard reduction potentials: the more positive E° half-reaction is the cathodic reduction and its reactant is the stronger oxidizing agent. However, predicting a reaction requires computing E°cell = E°cathode − E°anode, reversing the less-positive half-reaction, and balancing electrons and atoms.
• The instrument claims to predict spontaneity but does not state the required criterion E°cell > 0 for standard-state spontaneity, nor the equivalent relation ΔG° = −nFE°cell.
• A lookup of reduction potentials alone predicts standard-state thermodynamic direction, not actual reactivity under arbitrary concentrations, pressures, pH, complexation, passivation, or kinetic conditions.
• The phrase “metal/halogen reduction potentials” is narrower than the requested outputs, which may require nonmetal ions and polyatomic redox couples such as Fe3+/Fe2+ or Sn4+/Sn2+.

Units and conventions

• All listed E° values are standard reduction potentials in volts relative to the standard hydrogen electrode, whose E° is defined as 0.00 V.
• Standard conditions are assumed: approximately 25 °C, solutes at unit activity (often approximated as 1 M), gases at unit fugacity or approximately 1 bar, and pure solids or liquids in their standard states.
• Potential differences must be calculated in volts; values entered in millivolts must be divided by 1000 before comparison.
• The lookup table should identify phase, stoichiometry, solvent, temperature, and source-table convention because tabulated rounded values can vary slightly.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "cathode_candidate": "Cu2+ + 2e− ⇌ Cu(s)",
    "cathode_E0_V": 0.34,
    "anode_candidate": "Zn2+ + 2e− ⇌ Zn(s)",
    "anode_E0_V": -0.76
  },
  "expected_outputs": {
    "E0_values_V": {
      "Cu2+/Cu": 0.34,
      "Zn2+/Zn": -0.76
    },
    "reduced_species": "Cu2+",
    "oxidized_species": "Zn(s)",
    "balanced_reaction": "Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)",
    "E0_cell_V": 1.1,
    "standard_spontaneity": "spontaneous in the written direction"
  },
  "working": "Compare 0.34 V and −0.76 V: 0.34 V is more positive, so Cu2+ is reduced. Reverse the zinc reduction: Zn(s) → Zn2+ + 2e−. Add the half-reactions: Zn(s) + Cu2+ → Zn2+ + Cu(s). E°cell = E°cathode − E°anode = 0.34 − (−0.76) = 0.34 + 0.76 = 1.10 V. Since 1.10 V > 0, the reaction is standard-state spontaneous."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

An unrecognized species such as X3+/X produces an undefined lookup result. The instrument must explicitly reject it; otherwise downstream comparison and reaction prediction can propagate undefined or fabricated values.

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
• BOUNDARY_HAZARD_CATALOG.json