Unformatted text preview: Δ G o rxn = RT lnK 48.2 kJ (1000J / kJ) = (8.314 J/molK) (298 K) lnK lnK = 19.45 so K = 3.6 x 109 5. Calculate the temperature at which this reaction changes from being spontaneous to non spontaneous: Mg(s) + O 2 (g) ' MgO(s). Is the reaction spontaneous above or below this temperature? Set Δ G to zero to find the temp at which the rxn changes between spont and not spont 0 = Δ H T Δ S 0 = (1203 kJ) – T (0.2166 kJ/K) T = 1203 kJ / 0.2166 kJ/K T = 5554 Kelvin or 5281 o C rxn is spont BELOW this temp 6. Calculate Δ G for Mg(s) + O 2 (g) ' MgO(s) at 30.5 o C if the pressure of oxygen gas is 1.33 atm. Δ G = Δ G o rxn + RT lnQ Δ G = (1139 kJ) + (8.314 J/molK) (kJ / 1000J) (303.5 K) ln 1.331 Δ G = 1140 kJ = 1.140 x 10 3 kJ...
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 Thermodynamics, #, 298 K, 2 mg, 103 KJ, 216.6 J

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