(a) In Equation 13.1 which of the enthalpy terms for dissolving an ionic solid would correspond to the lattice energy? (b) Which energy term in this equation is always exothermic?

Short Answer

Expert verified
(a) In Equation 13.1, the lattice energy term corresponds to ΔH_1. (b) The energy term in Equation 13.1 that is always exothermic is ΔH_3 (solvation energy).

Step by step solution

01

Recall Equation 13.1

Equation 13.1 represents the dissolving of an ionic solid, and it is given as follows: ΔH = ΔH_1 + ΔH_2 + ΔH_3 ΔH_1: Represents the energy required to break the ionic solid into its constituent ions (Lattice energy) ΔH_2: Represents the energy required to overcome the forces holding the solvent molecules together (Solvent separation energy) ΔH_3: Represents the energy released when the ions are solvated, i.e., the energy change upon the interaction between solute ions and solvent molecules (Solvation energy)
02

Identify the lattice energy term

Given the components of Equation 13.1, we can now identify the lattice energy term. The lattice energy corresponds to the energy required to break the ionic solid into its constituent ions. In Equation 13.1, this is represented by ΔH_1. (a) The lattice energy term in Equation 13.1 is ΔH_1.
03

Determine the exothermic energy term

Next, we need to identify which energy term in Equation 13.1 is always exothermic. An exothermic process is one in which energy is released. Among the terms in Equation 13.1: - ΔH_1 (lattice energy) is endothermic since energy is required to break the ionic solid. - ΔH_2 (solvent separation energy) is also endothermic since energy is needed to overcome the forces holding the solvent molecules together. Since energy is released when the ions are solvated (when solute ions interact with the solvent molecules), we can conclude that: (b) The energy term in Equation 13.1 that is always exothermic is ΔH_3 (solvation energy).

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