Question

Question #f0842

Answer 1

Most endothermic reactions are not spontaneous

Explanation:

Some endothermic reactions are spontaneous because of a gain in entropy that more than overcomes the gain in heat energy.

An exothermic reaction results in a loss of heat energy to the surrounding environment. This is the direction of heat in the universe. So an endothermic reaction goes against the normal direction of heat in the universe.

It is much more likely that an exothermic reaction will be spontaneous than an endothermic reaction. However the gain in entropy is the normal direction of the universe and can overcome a gain in heat energy.

Answer 2

No

Explanation:

Nature favors reactions that are exothermic and have a positive entropy change. In other words, the most favorable reaction would have `DeltaH < 0` and `DeltaS > 0`.

This is because nature favors a lower energy, and an exothermic reaction by definition is going to a lower energy. Nature also favors disorder. If `DeltaS` is positive then the reaction is going to a greater level of disorder.

An endothermic reaction (`DeltaH >0`) may be spontaneous if the `DeltaS` is very positive. In this case, the reaction is said to be driven by entropy. These reactions are usually spontaneous at higher temperatures.

If `DeltaH >0` and `DeltaS < 0`, then the reaction will not be spontaneous because neither is favorable.