What is the Difference Between KH2PO4 and K2HPO4

The key difference between KH2PO4 and K2HPO4 is that KH2PO4 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. In other words, a monobasic compound can take up only one hydrogen ion or proton, while a dibasic compound can take up to two hydrogen ions or protons.

CONTENTS

1. Overview and Key Difference
2. What is KH2PO4 
3. What is K2HPO4
4. Similarities – KH2PO4 and K2HPO4 
5. KH2PO4 vs K2HPO4 in Tabular Form
6. Summary

What is KH2PO4?

KH2PO4 is monopotassium phosphate. It is also known as MKP, potassium dihydrogenphosphate, KDP, or monobasic potassium phosphate. 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, we can observe that this salt undergoes cocrystallization with dipotassium salt and also with phosphoric acid. However, we can see there are single crystals of KH2PO4 that are paraelectric at room temperature. They can become ferroelectric at low temperatures. In its commercially available form, KH2PO4 is a white powder that is deliquescent.

KH2PO4 can exist in different polymorphic structures. At room temperature, KH2PO4 occurs in paraelectric crystal form having tetragonal symmetry. At low temperatures, it can convert into ferroelectric crystal forms having orthorhombic symmetry. Besides, heating the substance to a high temperature can cause the formation of monoclinic KH2PO4. Upon further heating, this substance can convert into potassium metaphosphate KPO3 through the decomposition of KH2PO4.

When considering the production of KH2PO4, we can produce it by the reaction of phosphoric acid on potassium carbonate.

What is K2HPO4?

K2HPO4 is dipotassium phosphate. The other names for this compound are dipotassium hydrogen orthophosphate and potassium phosphate dibasic. It is an inorganic compound that is useful in fertilizer production, as a food additive and as a buffering agent. This substance appears as a white or colourless solid, which is water-soluble.

On a commercial scale, we can produce K2HPO4 by partial neutralization of phosphoric acid using two equivalents of potassium chloride compound.

We can use K2HPO4 as a food additive in imitation of dairy creamers, dry powder beverages, mineral supplements, and starter cultures. In addition, it can function as an emulsifier, a stabilizer, and as a texturizer, a buffering agent, chelating agents specifically for calcium in milk products, etc.

What are the Similarities Between KH2PO4 and K2HPO4?

1. KH2PO4 and K2HPO4 are useful in fertilizer production.
2. Both appear as a white powder that is deliquescent.
3. They are water-soluble.

What is the Difference Between KH2PO4 and K2HPO4?

The terms monobasic and dibasic refer to the number of potassium cations bound to the phosphate molecule. The key difference between KH2PO4 and K2HPO4 is that KH2PO4 is monobasic, so it can release a low amount of potassium, whereas K2HPO4 is dibasic, so it can release a high amount of potassium when used in fertilizer. Moreover, 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 to two hydrogen ions or protons.

The following infographic presents the differences between KH2PO4 and K2HPO4 in tabular form.

Summary – KH2PO4 vs K2HPO4

The terms monobasic and dibasic refers to the number of potassium cations bound to the phosphate molecule. The key difference between KH2PO4 and K2HPO4 is that KH2PO4 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.

Reference:

1. “Why Is KH2PO4 Monobasic and K2HPO4 Dibasic?” Answers, Answers Corporation.

Image Courtesy:

1. “Kaliumdihydrogenphosphat” By Bahmtec – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Hydrogenfosforečnan draselný” By Ondřej Mangl – Own work (Public Domain) via Commons Wikimedia