Here's why:

* General solubility rules: Most salts containing potassium (K⁺) are soluble in water.

* Specific to phosphates: While some phosphates are insoluble, potassium phosphate is an exception due to the high solubility of potassium salts.

Note: While KPO₄ is soluble, its solubility is not unlimited. You can dissolve a certain amount in water, but beyond that point, the solution becomes saturated.