Finding Temperature Where Reaction is Spontaneous

[Abigail Urbina 1K]

Why do we have to set delta G equal to zero when we are trying to find the temperature at which a reaction is spontaneous? I just find this a little confusing because I typically associate spontaneous reactions with negative values for delta G

[Lucian1F]

If you find it where G=0, you can figure out exactly what the temperature needs to be greater than or less than depending on the entropy for the reaction to be spontaneous

[Anna Li 2E]

You can also think about it like hypothetically what if we did set deltaG to a negative number? For example, you set deltaG=-1 and find the T value, you could set deltaG to an even smaller negative number, (ie -0.000001) and get a different temperature value. And so forth and so forth, always using a different deltaG value. We set deltaG=0 because while that in itself is not spontaneous, it is the threshold that helps us determine the range of T values where deltaG is negative.

You can view T as being ≥ or ≤ of a certain number rather than being exactly equal to a number.