Question

when is a subtance solube in water, what happens to lattice enthalpy and ionization enthalpy

Answer 1

During the dissolution of an ionic compound in water, the individual ions are surrounded by water molecule and there is decrease in overall energy. To pull the ions, the energy should be increased to overcome the lattice energy. If the lattice energy is larger than the energy of solvation of the ions the compound does not separate and becomes insoluble. Lattice enthalpy depends on the ionisation energy so the value of IE should be low for the compound to get soluble.