Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
A nonspontaneous process or reaction is one that does not occur naturally or without external intervention. It requires an input of energy to proceed.
Related terms
Gibbs free energy: A thermodynamic concept that combines both enthalpy and entropy changes to determine whether a process or reaction will be spontaneous or nonspontaneous.
Reversible reaction: A reaction that can proceed in both the forward and reverse directions. If the reverse reaction is more favorable, then the overall reaction may be nonspontaneous.
Standard conditions: Specific reference conditions (e.g., temperature, pressure) at which thermodynamic properties are measured. A chemical reaction might be spontaneous under normal conditions but become nonspontaneous under different conditions.