How do you know if a reaction is spontaneous or Nonspontaneous?

A spontaneous reaction is a reaction that occurs in a given set of conditions without intervention. Spontaneous reactions are accompanied by an increase in overall entropy, or disorder. … If the Gibbs Free Energy is negative, then the reaction is spontaneous, and if it is positive, then it is nonspontaneous.

What makes a reaction spontaneous?

Spontaneous Reactions. Reactions are favorable when they result in a decrease in enthalpy and an increase in entropy of the system. When both of these conditions are met, the reaction occurs naturally. … The combination of energy decrease and entropy increase dictates that combustion reactions are spontaneous reactions.

Under what conditions will a reaction be spontaneous?

When ΔS > 0 and ΔH < 0, the exothermic process is spontaneous as written, at any temperature. When ΔS < 0 and ΔH > 0, the process is never spontaneous, but the reverse process is always spontaneous.