Well, "lattice enthalpy is the enthalpy associated with the "
"formation of one mole of an ionic solid from equiv quantites"
"of its constituent ions, with the reactant specified to be in the"
"gas phase."
And thus, for the lattice enthalpy of "sodium chloride" we would interrogate the thermodynamics of the reaction:
Na^(+)(g) + Cl^(-)(g) rarr NaCl(s) +Delta,
where Delta-="Lattice enthalpy."
And while this is a hard measurement to make experimentally, there are enuff good thermodynamic data to allow the measurement by data from known experiments.
And "hydration enthalpy" is the "enthalpy associated with the"
"formation of one mole of hydrated ions from one mole of"
"gaseous ions that undergo hydration to give aquated ions."
M^(+)(g) + "excess water"rarr M^(+)(aq) +Delta
Again, the data are good enuff to allow recourse to tabulated measurements.
