The solubility of potassium chloride KCl in water at 25C is given as 34.21 g/100 mL of water. Since you have 100 mL of water, the maximum mass of KCl that can dissolve in it is:34.21 g KCl/100 mL water 100 mL water = 34.21 g KClSo, the maximum mass of potassium chloride that can dissolve in 100 mL of water at 25C is 34.21 grams.