Final answer:
The energy released per ion pair for the reaction Na(g) + Br(g) → NaBr(g) is calculated considering three processes. The dissociation energy, or the energy required to separate the NaBr unit into its ions, is calculated to be 4.26 eV. Thus, this is the energy released per ion pair in the reaction.
Step-by-step explanation:
The energy released per ion pair for the reaction Na(g) + Br(g) → NaBr(g) is calculated by considering three processes. First, the ionization of Na which requires 0.824 aJ of energy. Second, the natural affinity of Br for electrons, which releases 0.540 aJ of energy when it gains an electron. Lastly, the formation of the ionic bond between Na+ and Br- which releases more energy, referred to as lattice energy. The enthalpy change can be calculated using the equation Eform = Exfr + Ucoul + Uex. Here, Exfr represents the energy associated with the transfer of an electron from Na to Br, Ucoul represents the energy associated with the Coulomb attraction between the ions and Uex represents the energy associated with repulsion due to the exclusion principle.
The total energy change thus calculated is -4.26 eV considering the values quoted above. Therefore, the formation of a NaBr unit by ionic bonding is energetically favorable and contributes to the stability of the compound. The dissociation energy, which is the energy required to separate the NaBr unit into Na+ and Br- ions, is 4.26 eV. Thus, the energy released per ion pair of the given reaction is 4.26 eV.
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