Why are ionic compounds easily soluble in water?
1 Answer
Not all of them are!
Explanation:
Because water is polar the partially positive charged hydrogen atoms in the water molecule are attracted to the anions on the surface of the solid ionic lattice. At the same time, the partial negatively charged oxygen atom in water molecules is attracted to the cations. This means that water can associate with both the anions and the cations. When these attractive bonds are formed, energy is released and transfers to the cations and anions resulting in their vibrations becoming faster. The increased motion allows them to ultimately break from the lattice and form solutions.
In some cases, however, the energy released is not enough to break the ionic bonds between ions and cations in the lattice. So some ionic compounds are easily water soluble (e.g. NaCl) but others are not (e.g. MgO).
It is a classic school chemistry error to assume that "ionic compounds are soluble in polar solvents like water, but covalent compounds are soluble in non-polar solvents". There are two very well known covalent compounds that are soluble in water - sugar and ethanol.
