Why is KH2PO4 called monobasic?

KH2PO4 is monopotassium phosphate. It is also known as MKP, potassium dihydrogenphosphate, KDP, or Potassium Phosphate Monobasic. It is an inorganic compound that is often used as a fertilizer along with dipotassium phosphate. The three major uses of KH2PO4 are the production of fertilizers, as a food additive in the food industry, and as a buffering agent. Moreover, this salt undergoes cocrystallization with dipotassium salt and phosphoric acid. They can become ferroelectric at low temperatures. In its commercially available form, KH2PO4 is a deliquescent white powder.

K2HPO4 is dipotassium phosphate. The other names for this compound are dipotassium hydrogen orthophosphate and potassium phosphate dibasic. This substance appears as a white or colorless solid, which is water-soluble. Dipotassium phosphate is a highly water-soluble salt often used as a fertilizer and food additive as a source of phosphorus and potassium as well as a buffering agent.

The key difference between KH2PO4 and K2HPO4 is that Potassium Phosphate Monobasic is monobasic and can release a low amount of potassium, whereas K2HPO4 is dibasic and can release a high amount of potassium when used in fertilizer. The terms monobasic and dibasic refer to the number of potassium cations bound to the phosphate molecule. Monobasic KH2PO4 compound can take only one hydrogen ion or proton from its solution, whereas dibasic K2HPO4 compound has two potassium ions that can be exchanged for two hydrogen ions or protons.