What makes something spontaneous chemistry

A spontaneous reaction is one in which product formation is favored, even if the reaction is extremely slow. You do not have to worry about a piece of paper on your desk suddenly bursting into flames, although its combustion is a spontaneous reaction. What is missing is the required activation energy to get the reaction started. If the paper were to be heated to a high enough temperature, it would begin to burn, at which point the reaction would proceed spontaneously until completion.

In a reversible reaction, one reaction direction may be favored over the other. Carbonic acid is present in carbonated beverages. It decomposes spontaneously to carbon dioxide and water according to the following reaction. The forward reaction is spontaneous because the products of the forward reaction are favored at equilibrium.

In the reverse reaction, carbon dioxide and water are the reactants, and carbonic acid is the product. The reverse of the above reaction is not spontaneous. This illustrates another important point about spontaneity. Just because a reaction is not spontaneous does not mean that it does not occur at all.

Rather, it means that the reactants will be favored over the products at equilibrium, even though some products may indeed form. The rate of a reaction is independent of its spontaneity, and instead depends on the chemical kinetics of the reaction.

Every reactant in a spontaneous process has a tendency to form the corresponding product. This tendency is related to stability. An endergonic reaction also called a nonspontaneous reaction or an unfavorable reaction is a chemical reaction in which the standard change in free energy is positive, and energy is absorbed.

The total amount of energy is a loss it takes more energy to start the reaction than what is gotten out of it so the total energy is a negative net result. Endergonic reactions can also be pushed by coupling them to another reaction, which is strongly exergonic, through a shared intermediate.

Saul Steinberg from The New Yorker illustrates a nonspontaneous process here. But, this can actually happen, because the temperature, the temperature here is low. But, you have heat being released. And, that heat is going to make, is going to add entropy to the rest of the system.

So, still, The Second Law of Thermodynamics holds that the entropy of the universe is going to increase, because of this released heat. But, if you just look at the constituents here, the entropy went down. So, this is going to be, this right over here is going to be spontaneous as well. And, we're always wanting to back to the formula. If this is negative and this is negative, well, this is going to be a positive term. But, if 'T' low enough, this term isn't going to matter.

So, if 'T' is low, the entropy doesn't matter as much. Then, enthalpy really takes over. And, this is going to be spontaneous. Now, if you took that same scenario, but you had a high temperature, well now, you have these same two molecules. Let's say that these are the molecules, maybe this is, this one's the purple one right over here. You have the same two molecules here. Hey, they could get to a more kind of a, they could release energy.

But over here, you're saying, "Well, look, they could. But, they're buzzing past each other so fast that they're not gonna have a chance. Their electrons aren't gonna have a chance to actually interact in the right way for the reaction to actually go on. And so, this is a situation where it won't be spontaneous, because they're just gonna buzz past each other.

They're not gonna have a chance to interact properly. And so, you can imagine if 'T' is high, if 'T' is high, this term's going to matter a lot. And, so the fact that entropy is negative is gonna make this whole thing positive. And, this is gonna be more positive than this is going to be negative.

So, this is a situation where our Delta G is greater than zero. So, once again, not spontaneous. And, everything I'm doing is just to get an intuition for why this formula for Gibbs Free Energy makes sense.

And, remember, this is true under constant pressure and temperature. But, those are reasonable assumptions if we're dealing with, you know, things in a test tube, or if we're dealing with a lot of biological systems. Fortunately, this reaction is nonspontaneous at normal temperatures and pressures. Nitrogen monoxide is capable of being produced at very high temperatures and has been observed to form as a result of lightning strikes.

One must be careful not to confuse the term spontaneous with the notion that a reaction occurs rapidly. A spontaneous reaction is one in which product formation is favored, even if the reaction is extremely slow.

A piece of paper will not suddenly burst into flames, although its combustion is a spontaneous reaction. What is missing is the required activation energy to get the reaction started. If the paper were to be heated to a high enough temperature, it would begin to burn, at which point the reaction would proceed spontaneously until completion.

In a reversible reaction, one reaction direction may be favored over the other.