For a reaction given below C(s) + O2 (g) -> CO2 (g) + 394 kJ / mol The enthalpy of reaction is
Correct answer: B. -394 kJ / mol
- A. 394 kJ / mol
- B. -394 kJ / mol
- C. 197 kJ / mol
- D. -197 kJ / mol
Explanation
Formation of Carbon dioxide from Carbon and Oxygen is an exothermic reaction. Almost 394kJ of heat is produced or given off.From the equation it is seen that since it is an exothermic reaction-1 mole of CO2 releases 394kJ of heat and when energy is released enthalpy change is negative.(Please note that the"+394" in the question is NOT enthalpy change. It is simply the energy released with the reaction. The question requires us to determine the enthalpy change based on this information).
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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