Which enthalpy change is relevant in the following processNa(s) -> Na (g) ΔH = +107
Correct answer: A. Enthalpy of atomization
- A. Enthalpy of atomization
- B. Enthalpy of fusion
- C. Enthalpy of vaporization
- D. Enthalpy of formation
Explanation
Option A, enthalpy of atomization, is the energy required to completely separate all the atoms in a chemical substance. The separated atoms are in a gaseous state and get separated from the corresponding substance in its standard state. Sodium is solid in its standard state, and after atomization, the atoms are in their gaseous state. Hence, this is the correct answer. Option B is the enthalpy change when a solid substance melts into a liquid. Here, the state change is from a solid to a gas, no liquid state involved.Option C is the enthalpy change when a liquid is vaporized into a gas. Here, a solid is atomized to its gaseous state so, vaporization does not apply here.Option D is the enthalpy change when one mole of a substance is formed from its constituent elements. This does not describe the given reaction.
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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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