Source: https://guthlabs.ai/docs/instruments/standard-cell-potential-e-cell-calculator/mechanism/

instrument mechanism / verified-clean

# Standard Cell Potential (E°cell) Calculator mechanism

The inspectable method record for Standard Cell Potential (E°cell) Calculator, kept separate from implementation and qualification.

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

## Model scope

The core electrochemical formulas are standard and correct, but the specification does not state how n is obtained, how half-reaction direction and electron balancing are enforced, what standard conditions apply to the lookup table, or how the E°cell = 0 case is labeled. These ambiguities require review before release.

- E°cell = E°cathode − E°anode is the standard formula when both tabulated values are standard reduction potentials and the half-cell designated as the cathode is written as a reduction.

- ΔG° = −nFE°cell is correct, but n must be the number of electrons transferred in the balanced overall reaction; it cannot be inferred safely from only two unbalanced half-reaction selections.

- The spontaneity output must include an equilibrium case: E°cell > 0 is spontaneous, E°cell < 0 is nonspontaneous for the written reaction, and E°cell = 0 indicates equilibrium under standard conditions. Reporting only spontaneous/nonspontaneous is incomplete.

## Units and conventions

- Both E° values are standard reduction potentials in volts (V), at the same stated standard conditions, conventionally 25 °C, solutes at 1 M activity, gases at 1 bar or the table's specified standard pressure, and pure solids/liquids in their standard states.

- Use F = 96485 C mol⁻¹ e⁻. With E° in volts, ΔG° is obtained in J mol⁻¹; divide by 1000 for kJ mol⁻¹.

- n is dimensionless and is the balanced number of moles of electrons transferred per mole of overall reaction as written.

- The lookup-table entries must identify the chemical species, phase, temperature, and standard-state convention; CRC values can vary slightly by source and conditions.

- If users enter millivolts, the interface must convert mV to V before calculating; otherwise ΔG° will be wrong by a factor of 1000.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "cathode_half_reaction": "Cu²⁺ + 2e⁻ → Cu(s)",
    "E°cathode_V": 0.34,
    "anode_half_reaction": "Zn²⁺ + 2e⁻ → Zn(s)",
    "E°anode_V": -0.76,
    "n": 2,
    "F_C_per_mol_e": 96485
  },
  "expected_outputs": {
    "E°cell_V": 1.1,
    "spontaneity": "spontaneous",
    "ΔG°_J_per_mol": -212267,
    "ΔG°_kJ_per_mol": -212.267
  },
  "working": "E°cell = 0.34 − (−0.76) = 0.34 + 0.76 = 1.10 V. ΔG° = −nFE°cell = −(2)(96485 C mol⁻¹)(1.10 V) = −212267 C·V mol⁻¹ = −212267 J mol⁻¹ = −212.267 kJ mol⁻¹. Since E°cell > 0, the written cell reaction is spontaneous under standard conditions."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The plain-JavaScript arithmetic can overflow for extreme entered potentials, producing Infinity and -Infinity rather than a finite result. The convention probe also shows that reversing cathode/anode interpretation reverses both E°cell and spontaneity.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/standard-cell-potential-e-cell-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/standard-cell-potential-e-cell-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/standard-cell-potential-e-cell-calculator/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`

- `BOUNDARY_HAZARD_CATALOG.json`