CHEMISTRY COMMUNITY

What is most important in deciding if a reaction is spontaneous (ex enthalpy, entropy, Gibbs free energy)?

Gibbs Free Energy. If delta G is negative you know that the forward reaction is spontaneous.

Gibbs free energy change determines if a reaction is spontaneous under the conditions of constant pressure and constant temperature

Gibbs Free Energy (delta G) gives information about the spontaneity of a reaction. If deltaG<0, then the reaction is spontaneous.

If delta G (Gibbs free energy) is negative then you know that it was spontaneous.

Gibbs free energy will allow you to determine if the reaction is spontaneous or not (based on the sign). Also enthalpy can be used, as negative enthalpy means the reaction is exothermic since it is releasing heat.

Definitely Gibbs Free energy (delta G)! If delta G is negative then the reaction is spontaneous, but if it’s positive it is not.

Gibbs Free Energy is definitely the best indicator of spontaneity as it takes into account entropy and enthalpy.

Gibbs free energy is one of the easiest ways to determine whether a reaction is spontaneous or not. A negative delta G is spontaneous (exergonic) and a positive delta G is not spontaneous (endergonic).

annikaying wrote:What is most important in deciding if a reaction is spontaneous (ex enthalpy, entropy, Gibbs free energy)?

Personally, I think that Gibbs free energy is the best indicator because it combines enthalpy and entropy. Moreover, it's extremely clear cut: if delta G is negative, it is spontaneous; if delta G is positive, it is not spontaneous. However, this does not mean that you can't estimate if a reaction is spontaneous or not using enthalpy or entropy. It's just that Gibbs free energy is much more clear cut.

A negative delta G means that the reaction is spontaneous.

As everyone above said, Gibbs free energy is how you determine if a reaction is spontaneous or not. However, it might be important to remember that the reason Gibbs free energy is so clear cut is that it’s because it’s based off total entropy which is always increasing.

Delta G is the greatest determiner of whether a reaction will be spontaneous or not. If delta G is negative, then the reaction is spontaneous. You could also use the equation DeltaG= DeltaH- T*DeltaS, given either DeltaH or DeltaS, to see what values need to be in order to produce a spontaneous reaction.

Aside from delta G, a reaction is spontaneous if delta H is negative and delta S is positive.

jisulee1C wrote:Gibbs Free Energy. If delta G is negative you know that the forward reaction is spontaneous.

Why is it Gibbs Free Energy vs, using enthalpy or entropy.

Gibbs free energy, which is determined by enthalpy and entropy.

If a reaction has an increase in entropy or a decrease in enthalpy, then it is more likely to be spontaneous. To compute the actual value you need to check if the Gibbs free energy of a reaction is negative and to do that you use the equation delta G=deltaH-T*deltaS

Why exactly does delta G have to be negative to be considered spontaneous?

Gibbs free energy has to be negative. B/c delta G= Delta H - T*DeltaS the others contribute to delta G

Natalie Benitez 1E wrote:Why exactly does delta G have to be negative to be considered spontaneous?

If delta G is negative that means it is going from higher energy(reactants) to lower energy (products). If it is going from high to low, you need very little (if any input of energy) so it will happen spontaneously.
On the other hand when Delta G is positive, it is going from lower energy of reactants to higher energy of products. Because it is going from low to high, it needs an input of energy. The reaction will not take place unless there is this input which. is why it is not spontaneous

Gibbs free energy is usually a delta, so final minus initial. When delta G is negative the products have less gibbs free energy, making the reation spontaneous

If delta g, gibbs free energy, is a negative value, then the reaction in question can be determined to be spontaneous

To add on, when Gibbs free energy is negative that means that according the equation for gibbs free energy, delta S or change in entropy is positive and if change in entropy is positive, it means that a process is spontaneous.

If the delta g value is negative then the reaction is considered spontaneous.

when delta g is negative, the reaction is spontaneous and vice versa with positivity.

Gibbs free energy! If the delta g is negative then it is going to be spontaneous.

gibbs free energy!!

delta G is the most forward way to determine if the reaction is spontaneous or not.

Gibbs free energy is the best and most accurate way to tell whether a reaction is spontaneous, but using the equation delta G= delta H- T*delta S, it is possible to see what values of delta H and delta S gives a a negative delta G value.

Gibbs free energy is the best determinant. I think it's best since it includes both entropy and enthalpy in its formula. If it's negative it is spontaneous

Gibbs free energy can help determine spontaneity.

Gibbs free energy under conditions of constant temperature and pressure! your delta G must be negative because that is the energy free to do work!

the spontaneity does depend on the enthalpy and entropy as seen in the equation

Gibbs free energy is defined by a combination of enthalpy, temperature, and entropy. If Gibbs free energy is negative, that means the reaction is spontaneous, and if it is positive, the reaction will not be spontaneous. Note, spontaneity does NOT mean that the reaction will just proceed quickly, just that it is thermodynamically favorable. The largest factor is definitely enthalpy. Entropy can play a small role, but enthalpy usually dominates the spontaneity of a reaction.

gibbs free energy!!!!

Gibbs free energy determines whether a reaction is spontaneous or not. It is dependent on both delta H and delta S.

Hope it helps!

Gibs free energy is most important when determining if a reaction is spontaneous, when delta g is negative then the reaction is spontaneous.

Gibbs free energy would determine spontaneity because it measures the conditions under constant temperature and pressure.

DeltaG = DeltaH - DeltaS * T, when Delta G is negative, it is spontaneous, it can be negative when delta H is negative and Delta S is positive or high negative delta H and small negative deltaS or small positive deltaH and high positive DeltaS

The most important part when deciding if the reaction is spontaneous is determining Gibbs Free Energy. When delta G is negative that means the products have less free energy, hence making the reaction spontaneous.