Spontaneity of Exo and Endo reactions

[AditiSax]

Are exothermic reactions more likely to be spontaneous than endothermic reactions?

[Cienna Henry 1J]

Yes but not all spontaneous reactions are exothermic.

[Anjali_Kumar1F]

Why aren't all exothermic reaction spontaneous?

[kateminden]

Generally, exothermic reactions are more likely to be spontaneous than endothermic, but there are some instances when endothermic reactions are spontaneous. If the change in entropy at a given temperature is sufficient to overcome the unfavorable change in enthalpy, then the reaction will spontaneously occur, therefore making it a spontaneous endothermic reaction.

[ran2000]

Yes. But spontaneity is largely dependent on the 3 factors: enthalpy change, entropy change and temperature. Based on the values of each, the gibbs free energy is either positive or negative. Usually, however, exothermic reactions are more likely to be spontaneous because is H is less than 0, and since S is usually positive for exothermic reactions- G= negative. G= H-TS where H is negative and S is positive. Thus, G is usually negative and the reaction is spontaneous.