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Example Calculate Δ G m for water melting at -10ºC, +10ºC and 0ºC and predict which is / are spontaneous. Assume Δ H fusion (= 6.01kJ/mol) and Δ S fusion ( = 22.0 J/K.mol) are independent of temperature. Δ G = Δ H - T Δ S: Δ G (+10ºC ) = 6.01 kJ/mol - [283K x 0.022 kJ/K.mol] = - 0.22kJ/mol = SPONTANEOUS Δ G (0ºC ) = 6.01 kJ/mol - [273K x 0.022 kJ/K.mol] = 0 kJ/mol = AT EQUILIBRIUM Δ G (-10ºC ) = 6.01 kJ/mol - [263K x 0.022 kJ/K.mol] = + 0.22kJ/mol = NOT SPONTANEOUS ice below zero doesn’t suddenly melt. Water above zero doesn’t suddenly freeze! example: Here’s a chemical reaction: Calculate Δ G: 2Na (s) + 2H 2 O (l) --> 2NaOH (aq) + H 2(g) Δ G = [(2 x -470.11kJ/mol )+ 0] - [(2x0)+(2x-237.13kJ/mol)] = -940.22kJ/mol - (-474.26kJ/mol) = - 465.96kJ/mol ie spontaneous… and as we saw, also happens to be fast! o reactants n o products n o 298 G n G n G = Δ

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example2: Here’s a famous chemical reaction:Haber-Bosch Process: N 2(g)
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