Question

A reaction has a ΔH value of +120 kJ and a ΔS value of -42 J/K. At which of the following temperatures is the reaction spontaneous (meaning ΔG is negative)?

Answer 1

the reaction is spontaneous at T > 2900 K

Step-by-step explanation:

• ΔG = ΔH - TΔS

∴ ΔH = +120 KJ

∴ ΔS = (-42 J/K)*(KJ/1000 J) = -0.042 KJ/K

∴ ΔG < 0 ⇒ the reaction is spontaneous

⇒ at T = 2900 K:

⇒ ΔG = 120 - (2900)(-0.042) = 120 - 121.8 = - 1.8 KJ < 0