Chem Spontaneity

What does a negative ΔG mean?

A process is spontaneous.

What does a positive ΔG mean?

A process is nonspontaneous.

If ΔH is negative and ΔS is positive, when is the reaction spontaneous?

Spontaneous at all temperatures

If ΔH is positive and ΔS is negative, when is the reaction spontaneous?

Never spontaneous

If ΔH is negative and ΔS is negative, when is the reaction spontaneous?

Spontaneous at low temperatures
Nonspontaneous at high temperatures

If ΔH is positive and ΔS is positive, when is the reaction spontaneous?

Spontaneous at high temperatures
Nonspontaneous at low temperatures

What equation determines spontaneity?

ΔG = ΔH − TΔS

How does temperature affect reactions with positive ΔS?

Higher temperature makes −TΔS more negative, favoring spontaneity.

How does temperature affect reactions with negative ΔS?

Higher temperature makes −TΔS more positive, reducing spontaneity.