Question

Why are nitrates always soluble?

Answer 1

This is largely an entropy phenomenon. The nitrate ion is not very charge dense, and the negative charge is distributed over 4 centres.

Explanation:

Because the nitrate is not charge dense, the species in solution is less polarizing (as the nitrate ion, `NO_3^-`), and causes less solvent order upon dissolution. For this reason, many nitrate salts have solubility in non-aqueous solvents. Inorganic chemists generally do not exploit this solubility, because the nitrate ion is still a potent oxidant, although in the aqueous phase this reactivity is somewhat masked.