PROBLEM: Heating some metal carbonates, among them magnesium carbonate, leads to their decomposition. MgCO3(g) → MgO(s) + CO2(g) (a) Calculate.

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PROBLEM: Heating some metal carbonates, among them magnesium carbonate, leads to their decomposition. MgCO3(g) → MgO(s) + CO2(g) (a) Calculate DrH° and DrS° for the reaction. (b) Is the reaction spontaneous under standard conditions at 298 K? (c) Is the reaction predicted to be spontaneous at higher temperatures? rHº = fHº[MgO(s)] + fHº[CO2(g)] – fHº[MgCO3(s)] rHº = 1 mol (–601.24 kJ/mol) + 1 mol (–393.509 kJ/mol) – 1 mol (–1111.69 kJ/mol) rHº = 116.94 kJ/mol-rxn rSº = Sº[MgO(s)] + Sº[CO2(g)] – Sº[MgCO3(s)] rSº = 1 mol (26.85 J/K·mol) + 1 mol (213.74 J/K·mol) – 1 mol (65.84 J/K·mol) rSº = 174.75 J/K·mol-rxn

(b) rGº = rHº – TrSº = 116.94 kJ/mol-rxn – (298 K)(174.75 J/K·mol-rxn)(1 kJ/103 J) rGº = 64.87 kJ/mol-rxn The reaction is predicted to be non-spontaneous at 298 K (rGº > 0) (c) The reaction is predicted to be spontaneous at higher temperatures.