Final answer:
The Born-Haber cycle is a thermochemical cycle used to estimate lattice energies by breaking down the formation of an ionic solid into individual steps such as sublimation, ionization, and electron affinity, and combining these values using Hess's law.
Step-by-step explanation:
The Born-Haber Cycle
The Born-Haber cycle is a thermochemical cycle that facilitates the calculation of lattice energies for ionic compounds. To explain this concept, let's consider the formation of sodium chloride (NaCl) from its elements.
-
- First, sodium (Na) must be converted from its solid form to a gaseous atom, which is called sublimation.
-
- Next, chlorine (Cl2) gas is converted to two chlorine atoms.
-
- Then, the sodium atom in the gas phase loses an electron to form a sodium cation (Na+), a process which is referred to as ionization.
-
- Meanwhile, chlorine atoms gain an electron to become chloride anions (Cl-), known as electron affinity.
-
- Finally, Na+ and Cl- combine to form the ionic solid NaCl, releasing energy known as the lattice energy.
By using the individual enthalpy changes of these steps and applying Hess's law, one can estimate the lattice energy of NaCl even though this energy cannot be measured directly.