Source: https://guthlabs.ai/docs/instruments/reaction-quotient-q-vs-kc-kp-comparator/mechanism/

instrument mechanism / verified-with-binding-errata

# Reaction Quotient (Q) vs Kc/Kp Comparator mechanism

The inspectable method record for Reaction Quotient (Q) vs Kc/Kp Comparator, kept separate from implementation and qualification.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **verified-with-binding-errata**

## Model scope

The core equilibrium comparison and ΔG equation are standard under explicit activity and standard-state assumptions. Verdict is NEEDS_REVIEW because the specification ambiguously presents raw concentrations/pressures as Q inputs, does not define standard states or phase omission, and lists ΔG as an output without requiring T and R. Vector 2 exposes and corrects an exponent-sensitive arithmetic issue: with NH3=0.01, Q is 0.0001, so the supplied corrected value NH3=0.10 is used for the stated expected output.

- The comparison rules Q<K => forward and Q>K => reverse are correct only when Q and K use the same reaction, stoichiometric coefficients, phase treatment, and standard-state convention; the Q=K case should explicitly return no thermodynamic driving direction.

- Q should be written in terms of dimensionless activities: Q=Πa_products^ν/Πa_reactants^ν. Raw concentrations or pressures require normalization by specified standard states; otherwise Q can carry units.

- Kc and Kp are not interchangeable. The spec must require the selected quotient type to match the supplied equilibrium constant and must define whether pure solids and liquids are omitted.

- The ΔG relation ΔG=-RT ln(K/Q) is correct and equivalent to RT ln(Q/K), but the listed inputs omit temperature T, the gas constant R, and the required standard-state convention. It is valid for dimensionless Q and K and for the reaction as written.

## Units and conventions

- For concentration quotients, each concentration is divided by c°=1 mol/L before exponentiation; Kc is dimensionless under this convention.

- For pressure quotients, each pressure is divided by p°=1 bar or 100 kPa as explicitly stated; Kp is dimensionless under this convention.

- R=8.314 J mol^-1 K^-1 and temperature is in kelvin; reported ΔG values below are in kJ mol^-1 per reaction as written.

- Ideal-solution and ideal-gas behavior is assumed; otherwise activities or fugacities are required instead of raw concentrations or pressures.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "reaction": "N2 + 3 H2 ⇌ 2 NH3",
    "quotient_type": "Kc",
    "concentrations_mol_L": {
      "N2": 0.5,
      "H2": 0.8,
      "NH3": 0.2
    },
    "standard_concentration_mol_L": 1,
    "K": 0.04,
    "T_K": 298,
    "R_J_mol_K": 8.314
  },
  "expected_outputs": {
    "Q": 0.15625,
    "shift_direction": "reverse",
    "delta_G_kJ_mol": 3.3759
  },
  "working": "Q=(a_NH3^2)/(a_N2*a_H2^3)=(0.20/1.0)^2/[(0.50/1.0)*(0.80/1.0)^3]=0.0400/(0.50*0.512)=0.0400/0.256=0.15625. Since Q=0.15625>K=0.040, the shift is reverse. RT=(8.314*298)/1000=2.477572 kJ mol^-1. ΔG=-RT ln(K/Q)=-2.477572 ln(0.040/0.15625)=-2.477572 ln(0.256)=+3.3759 kJ mol^-1."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

A zero reactant concentration makes the Q denominator vanish, producing an undefined result that must be rejected. Direction labels are also ambiguous unless the reaction orientation used to define forward and reverse is explicitly documented.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/reaction-quotient-q-vs-kc-kp-comparator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/reaction-quotient-q-vs-kc-kp-comparator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/reaction-quotient-q-vs-kc-kp-comparator/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-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`