The solubility of potassium nitrate KNO3 at 25C in water is given as the maximum amount of solute that can dissolve in a given amount of solvent. In this case, the maximum amount of KNO3 that can dissolve is 31.6 g in 100 mL of water.To express the solubility, we can use the unit grams per 100 milliliters g/100 mL . Therefore, the solubility of potassium nitrate KNO3 at 25C in water is 31.6 g/100 mL.