Gibbs Free Energy Calculator

Calcolatore dell’Energia Libera di Gibbs

Unità predefinite: ΔH in kJ/mol, ΔS in J/(mol·K), T in K.
Costanti: R = 8.314462618 J/(mol·K) = 0.008314462618 kJ/(mol·K).

Impostazioni
Se usi °C, convertiamo a K: T(K)=t(°C)+273.15
A) ΔG = ΔH − TΔS
Conversione automatica: ΔS (J→kJ) prima di moltiplicare per T.
B) ΔG° ↔ K (a T nota)
Formule: ΔG° = −RT ln K ; K = exp( −ΔG° / RT ) (R in kJ/(mol·K), T in K).
C) ΔG da ΔG° e Q
Se Q = K allora ΔG = 0 (condizione d’equilibrio).
D) Temperatura di equilibrio (ΔG = 0)
\( T_{eq} = \dfrac{\Delta H}{\Delta S} \) con ΔS convertito in kJ/(mol·K). Se ΔH e ΔS hanno segni opposti, l’equilibrio non è ottenibile con T reale costante.
Segno di ΔG: ΔG<0 spontanea (a T,P costanti), ΔG>0 non spontanea, ΔG=0 equilibrio. Attenzione alle unità e alla temperatura: K dipende da T.

Gibbs Free Energy Calculator (ΔG, ΔG°, K, Q, T Relationships)

The Gibbs Free Energy Calculator by UtileApp lets you quickly compute ΔG, ΔG°, the equilibrium constant (K), and their dependence on reaction quotient (Q) and temperature (T). It integrates the main thermodynamic relationships, with consistent units and automatic conversions (e.g., ΔS from J to kJ).

Main features

  • Gibbs equation:
    ΔG = ΔH − TΔS, with ΔH in kJ/mol, ΔS in J/(mol·K), and T in K (°C values are automatically converted).
  • Equilibrium relationship:
    ΔG° ⇄ K at the selected temperature, using
    ΔG° = −RT ln K and K = e^(−ΔG° / (RT)).
  • Reaction quotient adjustment:
    ΔG = ΔG° + RT ln Q, with automatic evaluation of the reaction direction (forward or reverse).
  • Equilibrium temperature:
    When ΔG = 0, T_eq = ΔH / ΔS.
  • Additional controls:
    Adjustable precision (decimal places) and customizable gas constant R (in kJ·mol⁻¹·K⁻¹).

Use and benefits

Perfect for students, teachers, and laboratory professionals, this calculator helps you:

  • Verify reaction spontaneity (ΔG < 0);
  • Derive K from tabulated ΔG° data;
  • Analyze how concentration (Q) and temperature affect equilibrium position.

The interface provides clear, immediate results with standardized scientific units — ideal for both learning and lab verification.

Example calculations

  1. ΔH = −92.2 kJ/mol; ΔS = −198 J/(mol·K); T = 298.15 K → compute ΔG.
  2. At T = 298 K, ΔG° = −5.7 kJ/mol → K ≈ e^(5.7 / (RT)).
  3. With known ΔG° and Q = 0.10 or 10 → evaluate the sign of ΔG and the reaction direction.

Notes

  • Always use temperature in Kelvin; the app automatically converts °C to K.
  • K values depend on temperature — ensure ΔH, ΔS, and T refer to the same thermodynamic state or conditions.