The heat of combustion of graphite to CO2(g) is -393.5 kJ/mole. The heat released in the formation of 35.2 g of CO2(g) from graphite and oxygen gas will be (approximately):
Correct answer: D. 315 kJ
- A. 379 kJ
- B. 215 kJ
- C. 208 kJ
- D. 315 kJ
Explanation
First, convert the mass of CO₂ to moles: 35.2 g / 44 g/mol = 0.8 mol. The heat released is then the number of moles multiplied by the molar heat of combustion: 0.8 mol × 393.5 kJ/mol ≈ 315 kJ.
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About Enthalpy
Enthalpy is the heat content of a system measured at constant pressure, and its change indicates whether a reaction or physical process is endothermic or exothermic. The topic covers state functions, enthalpy diagrams, standard enthalpy of formation, combustion and neutralisation, and the relationship between ΔH and internal energy change.
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