Question: why is potassium nitrate soluble in water?
Answer: Nitrates are soluble in water, so the nitrate in the potassium nitrate is soluble. This is possible because the solubility product constant (Ksp) of the potassium is such that solvation is possible, and solvation of the nitrate is possible because the Ksp of nitrate ion is favorable. ... This makes the ions solvated.