At 25°C,when 1.00 g of sulfur is burned at constant pressure in excess oxygen to give SO₂(g),9.28 kJ of heat is liberated.What is the enthalpy of formation of SO₂(g)?

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Quizplus · Accepted Answer

The enthalpy change given is for burning 1.00 g of sulfur. To find the enthalpy of formation per mole of SO₂, convert 1.00 g of sulfur to moles (1.00 g / 32.07 g/mol = 0.0312 mol) and then divide the heat released by the moles of sulfur: 9.28 kJ / 0.0312 mol = 297.44 kJ/mol, which rounds to -298 kJ/mol. The negative sign indicates that the reaction is exothermic.