K2HPO4 vs. KH2PO4

What's the Difference?

K2HPO4 and KH2PO4 are both phosphate salts that contain phosphorus, hydrogen, oxygen, and potassium ions. The main difference between the two compounds lies in their ratio of potassium ions to phosphate ions. K2HPO4 has two potassium ions for every phosphate ion, while KH2PO4 has only one potassium ion for every phosphate ion. This difference in composition leads to variations in their properties and applications. K2HPO4 is often used as a buffering agent in the food industry, while KH2PO4 is commonly employed as a fertilizer due to its high phosphorus content.


SynonymsPotassium phosphate dibasicPotassium phosphate monobasic
Chemical FormulaK2HPO4KH2PO4
Molar Mass174.18 g/mol136.09 g/mol
AppearanceWhite crystalline powderWhite crystalline powder
SolubilitySoluble in waterSoluble in water
pH8.2 - 9.2 (1% solution)4.5 - 5.5 (1% solution)
UsesBuffering agent, fertilizerBuffering agent, food additive

Further Detail


When it comes to chemical compounds, understanding their attributes and differences is crucial for various applications. In this article, we will compare the attributes of two important compounds: K2HPO4 and KH2PO4. Both compounds belong to the phosphate family and have distinct characteristics that make them suitable for different purposes. By exploring their properties, solubility, uses, and potential applications, we can gain a comprehensive understanding of these compounds.


K2HPO4, also known as dipotassium phosphate, is an inorganic salt with the chemical formula K2HPO4. It appears as a white crystalline powder with a molecular weight of 174.18 g/mol. The compound has a melting point of approximately 340°C and a density of 2.44 g/cm³. On the other hand, KH2PO4, or monopotassium phosphate, has the chemical formula KH2PO4 and appears as colorless crystals. It has a molecular weight of 136.09 g/mol, a melting point of around 253°C, and a density of 2.338 g/cm³.

Both compounds are highly soluble in water, which makes them suitable for various applications. K2HPO4 has a solubility of approximately 110 g/100 mL at 20°C, while KH2PO4 has a solubility of about 22 g/100 mL at the same temperature. This difference in solubility can be attributed to the presence of different ions in each compound.


K2HPO4 and KH2PO4 have distinct uses due to their unique properties. K2HPO4 is commonly used as a buffering agent in the food industry, where it helps regulate the pH of processed foods. It is also utilized as a fertilizer additive to provide essential nutrients to plants. Additionally, K2HPO4 finds applications in the pharmaceutical industry as a source of phosphorus and potassium in various medications.

On the other hand, KH2PO4 is widely used as a food additive, particularly in the production of soft drinks and baking powders. It acts as a pH regulator and stabilizer, ensuring the desired taste and texture of the final product. KH2PO4 is also utilized in the cultivation of microorganisms in laboratories and as a buffering agent in biochemical research.


As mentioned earlier, both K2HPO4 and KH2PO4 are highly soluble in water. However, their solubility varies due to the different ions present in each compound. K2HPO4 dissociates into two potassium ions (K+) and one phosphate ion (HPO4²⁻) in solution. On the other hand, KH2PO4 dissociates into one potassium ion (K+) and one phosphate ion (H2PO4⁻). The presence of an additional potassium ion in K2HPO4 increases its solubility compared to KH2PO4.

The solubility of K2HPO4 and KH2PO4 can also be affected by temperature. Generally, the solubility of most salts increases with temperature. However, the solubility of KH2PO4 decreases slightly with increasing temperature, while the solubility of K2HPO4 remains relatively constant. This difference in solubility behavior can be attributed to the different crystal structures and intermolecular forces present in each compound.

Potential Applications

Due to their unique properties, K2HPO4 and KH2PO4 have potential applications in various fields. K2HPO4, with its higher solubility and additional potassium ion, can be used as a nutrient supplement in hydroponic systems for plant growth. It provides essential macronutrients to plants, promoting healthy development and increased crop yields.

On the other hand, KH2PO4's pH-regulating properties make it suitable for use in the cosmetics industry. It can be incorporated into skincare products to adjust the pH levels, ensuring optimal skin compatibility and stability of the formulations. Additionally, KH2PO4's buffering capacity makes it useful in the formulation of pharmaceuticals, where it helps maintain the desired pH of medications.


In conclusion, K2HPO4 and KH2PO4 are two important compounds with distinct attributes and applications. K2HPO4, with its higher solubility and additional potassium ion, finds uses in the food, pharmaceutical, and agricultural industries. On the other hand, KH2PO4's pH-regulating properties make it suitable for applications in the food, cosmetics, and pharmaceutical industries. Understanding the properties and potential applications of these compounds allows us to harness their benefits in various fields, contributing to advancements in science, technology, and everyday life.

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