Spontaneous as Written

[Catherine Bubser 2C]

A reaction is spontaneous as written if delta G is negative, correct?

[Sabina House 2A]

If the delta G of a reaction is negative, then that reaction will be spontaneous under those conditions. I'm not sure what you mean by spontaneous as written, but I hope this answers your question!

[Anh Trinh 1J]

A reaction is spontaneous as written when and , then .

[BKoh_2E]

That is correct. It is also good to understand that if ΔS_univis positive, then ΔG_rxn is negative. Therefore, the reaction would be spontaneous.

[Samudrala_Vaishnavi 3A]

Yes, this could be due to two reasons, the change in entropy being positive (which makes sense since the more chaos or entropy you get, the more spontaneously it could have happened since that's how things naturally work) or due to the enthalpy change being more negative (so less order or enthalpy occurs).

[Alexandra Salata 2L]

The negative value of ΔG° indicates that the reaction is spontaneous as written.

[LeanneBagood_2F]

wait, can someone please explain what exactly is meant when we say "as written"? has that phrasing ever been mentioned in lecture, if so when/which one?

[Brian Nguyen 2I]

Yes, that's correct. If delta G is negative, then the reaction is always considered spontaneous.

[Sheryl Ocampo 1D]

Yup, that is the way to determine if a reaction is spontaneous

[Megan Singer 3D]

What everyone said above is correct, but make sure you look at ΔG° vs ΔG. For a reaction to be spontaneous, only its ΔG has to be negative, not its ΔG° (which is the ΔG for that reaction at standard conditions). This is relevant when you're looking at reactions that aren't taking place under standard conditions. If you need to calculate the ΔG from the ΔG°, use the equation ΔG = ΔG° + RTlnQ.

[MMorcus2E]

Yes, that is correct. A negative delta G means that the reaction is spontaneous and comes from the fact that temperature*deltaS (entropy) is higher than deltaH (enthalpy). I would also like to emphasize the comment that Megan posted about the difference between deltaG0 (which is a set value that depends on what the reaction that we're looking at is at standard temperature and pressure condition) and deltaG.