Calculate ΔG from enthalpy, entropy, and temperature to see whether a reaction is spontaneous as written.
| ΔG (J) | – |
Use this calculator for thermo homework when you have ΔH and ΔS and a temperature and need the sign of ΔG.
ΔG = ΔH − TΔS. Type ΔH in J (or J/mol) and ΔS in J/K on the same mole basis. Enter temperature in °C or °F; the calculator converts to kelvin. Temperature must be above −273.15 °C. Negative ΔG is spontaneous as written, at that T only. This uses the two-term Gibbs equation; it does not integrate heat capacities.
ΔH (J): ΔH in joules (per mole if ΔS is per mole). −92000 for a typical combustion-scale value.
ΔS (J/K): ΔS in J/K on the same basis. Watch the sign: gases produced usually raise ΔS.
Temperature: Temperature in °C or °F. 25 °C is standard; 0 °C is ice point.
ΔG (J): Gibbs energy change on the same basis as ΔH.
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