Exercise 2 | Chemical Thermodynamics

Give the signs of ΔH and ΔS for the following observations:


- the reaction is never spontaneous

- the reaction is spontaneous only at low temperatures

- the reaction is spontaneous only at high temperatures

ΔG = ΔH – TΔS

Spontaneity of reaction if ΔG < 0


- the reaction is never spontaneous:

⇒ ΔG < 0 ⇒ ΔH: (+) and ΔS: (-)

- the reaction is spontaneous only at low temperatures (ΔG ≈ ΔH):

⇒ ΔG > 0 ⇒ ΔH: (-) and ΔS: (-)

- the reaction is spontaneous only at high temperatures (ΔG ≈ – TΔS):

⇒ ΔG > 0 ⇒ ΔS: (+) and ΔH: (+)