Reaction Quotient (Q) vs Kc/Kp Comparator

Inspectable records

Ledger state

The current ledger marks this instrument verified with errata that must be applied at binding time.

Area

Chemistry & Materials

Tranche

tranche-4

Evidence ID

t4-099

Ledger rows

1

No ledger note is attached.

Review findings

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.

Formula and scope findings

• 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.

Unit assumptions

• 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.

Boundary hardening

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.

Errata and corrections

Tranche errata

Inspectable example

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

{
  "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."
}

Related workflows

Sources and evidence

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

• VERIFIED_LEDGER.json · VERIFIED_WITH_ERRATA
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json