Why is deltaG negative and spontaneous?

[LyahFitzpatrick 2E]

If entropy and enthalpy are both spontaneous and positive values, why is deltaG spontaneous when negative?

[Ashwin Vasudevan 3A]

Reactions with a negative ∆G release energy, which means that they can proceed without an energy input (are spontaneous). In contrast, reactions with a positive ∆G need an input of energy in order to take place.

[cnyland]

delta G is spontaneous when negative, this was discussed during the lecture where professor lavelle derived the delta G = deltaH - TdeltaS equation!

[mmcqueen]

The negative value refers to the fact that energy is released when deltaG is spontaneous.

[705968973]

In the case of entropy, it is spontaneous with a positive value. However, in the case of enthalpy, reactions are usually spontaneous when it is negative because exothermic reactions do not require any input of energy to get the reaction started. Delta G refers to the difference in free energy between the products and the reactants. If the difference in free energy between the products and reactants is negative, this means that the products possess less free energy than the reactants. This means that the reaction had more free energy to begin with on the reactant side which makes the reaction spontaneous. This is why reactions are spontaneous with negative delta G.