spontaneous reactions

[Jasleen Kahlon]

What exactly does a reaction being spontaneous mean in terms of thermodynamics, and what occurs when ∆S and ∆H are either both negative or both positive?

[Ashley Wang 4G]

A spontaneous reaction means it will tend to occur under the given conditions without an outside source of energy. Note that it says nothing about the speed of the reaction!

When ∆S and ∆H are either both negative or both positive, that is when the temperature dependence of the reaction becomes very important, as the magnitude of T will determine whether the reaction will be spontaneous.

Hope this helps!

[saigorijavolu2k]

A negative delta S means that the reverse reaction is spontaneous. A positive delta S means that the forward reaction is spontaneous. A negative delta H means that it is exothermic and usually exothermic reactions are associated with being spontaneous because they release energy.