exothermic reactions

[Cristina Subratie 1C]

why aren't all exothermic reactions spontaneous if they do not require energy? is there a real life example of an exothermic reaction that is not spontaneous

[Annaleese Ramos 1E]

Not all exothermic reactions are spontaneous because spontaneity depends on the release of energy as well as the change in entropy and temperature. If the temperature is low or there is a significant decrease, it might not be spontaneous.

[Adithi Nayak 2G]

Not all exothermic reactions are spontaneous because spontaneity depends on entropy and temperature, in addition to enthalpy. Even though enthalpy is negative in exothermic reactions, if entropy is negative the TdeltaS term in the deltaG = deltaH - T*deltaS equation also becomes negative. Two negative make a positive, so this could create an overall positive deltaG value. That would make the reaction not spontaneous.

[106268412]

It really relies on the temperature and the entropy value. Because of the G = H - TdeltaS equation, a high temperature and negative entropy can override the favorable exothermic conditions. This is pretty rare though, I would assume, because often exothermic reactions have an increase in entropy.

[KevinG_1G]

Hi!

Not all exothermic reactions are spontaneous because spontaneity depends on both enthalpy and entropy as the equation ∆Gº=∆Hº-T∆Sº shows. Some exothermic reactions might have a negative entropy change, making them non-spontaneous when T is increased.

An example is the conversion of diamond to graphite, which releases heat but requires an increase in entropy, making it non-spontaneous at low temperatures.

[206190205]

Hello,
Not all exothermic reactions are spontaneous because they rely on other conditions such as how much energy is being released and the temperature. Another condition that you would have to look at is the change in entropy.
Hope this helps.