# Temperature dependence of ΔS°, ΔG° and ΔH°

Homework Helper
Gold Member
2020 Award
I was taught that standard ΔS°, ΔG° and ΔH° are the corresponding quantities measured under standard conditions which I was told was 0.1M for solutions, 1 bar for gases, but importantly also at 298K.

On many places on the internet, however, I have read that 298K is not actually a standard condition. Instead, we can find values for ΔS°, ΔG° and ΔH° for all temperatures.

This makes sense, since considering the definition of ΔG°, for instance,

ΔG° = ΔH° - TΔS°

it would be silly for ΔG° to be fixed at 298K considering that we can choose T to be whatever we want. I thought it should be read more like "The standard change Gibbs energy at e.g. 500K is ΔH° (at 500K) subtract 500K x ΔS° (at 500K).

A common approximation at my level is that ΔH° and ΔS° don't change with temperature, so when calculating ΔG° we can still use the values of ΔH° and ΔS° for 298K. However, this ΔG° would correspond to the reaction under standard conditions at the specified temperature.

I was wondering if anyone could check if I am understanding this correctly? Thank you :)