Difference Between Phosphate and Orthophosphate

Main Difference – Phosphate vs Orthophosphate

Phosphates are compounds composed of PO₄ units. They are salts or esters of phosphoric acid. Orthophosphate is the simplest among other phosphates. It is composed of only one phosphate unit. Thus, it is also known monophosphate. Phosphates are naturally occurring minerals. These minerals are mined to get phosphorous required for the production of fertilizers. The main difference between phosphate and orthophosphate is that phosphate is any compound composed of phosphate units whereas orthophosphate is composed of one phosphate unit.

Key Areas Covered

1. What is Phosphate
     – Definition, Chemical Properties, Examples
2. What is Orthophosphate
     – Definition, Different Terms
3. What is the Difference Between Phosphate and Orthophosphate
      – Comparison of Key Differences

Key Terms: Apatite, Fertilizers, Minerals, Orthophosphate, Phosphate, Salts

What is Phosphate

The term phosphate is used to name any salt or ester of phosphoric acid or the anion of the phosphoric acid. The chemical formula for phosphate is –PO₄^-3. Phosphate ion has the molar mass 94.97 g/mol.

Figure 1: Ball-and-Stick Model of Phosphate

The structure of phosphate anion includes a phosphate atom at the center, bonded to four oxygen atoms. The geometry of this anion is tetrahedral. The phosphate anion has -3 charge. When this anion is bound to a hydrogen atom, it is known as phosphoric acid (H₃PO₄).

Phosphate salts are ionic compounds. Here, a positively charged ion or a cation is bonded to a phosphate ion via ionic bonds. Many phosphates are not water soluble. But phosphates of group 1 elements and ammonium phosphate are water-soluble ionic compounds.

Phosphate minerals are the major natural source of obtaining phosphorous. The most common phosphate minerals include apatite, phosphorite, fluorapatite, etc. These mineral deposits are mined to get phosphorous required for the production of fertilizers.

What is Orthophosphate

Orthophosphate is any salt or ester of orthophosphoric acid. When H+ ions are lost from orthophosphoric acid, orthophosphate anion is formed. The chemical formula of orthophosphate anion is –PO₄^-3 and the molar mass is 94.97 g/mol.

Figure 2: Phosphoric Acid Series

This is also called phosphate anion in common since orthophosphate is the simplest among the members of the phosphate series. It is also called monophosphate because it is composed of one phosphate unit. Other members of the phosphate series have two or more phosphate units.

Difference Between Phosphate and Orthophosphate

Definition

Phosphate: Phosphate refers to any salt or ester of phosphoric acid or the anion of the phosphoric acid.

Orthophosphate: Orthophosphate refers to any salt or ester of orthophosphoric acid.

Usage

Phosphate: The term phosphate is used to name any compound having one or more PO₄ units.

Orthophosphate: The term orthophosphate is used to name phosphates with only one PO₄ unit.

Conclusion

Phosphates are very important in fertilizer production. Orthophosphates are normal phosphates which are composed of one phosphate unit per molecule. The main difference between phosphate and orthophosphate is that phosphate is any compound composed of phosphate units whereas orthophosphate is composed of one phosphate unit.

References:

1. “Phosphoric acids and phosphates.” Wikipedia, Wikimedia Foundation, 18 Aug. 2017, Available here.
2. “Phosphate minerals.” Wikipedia, Wikimedia Foundation, 18 Nov. 2017, Available here.

Image Courtesy:

1. “Phosphate-3D-balls” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia
2. “Various Phosphoric Acids” By . H Padleckas – Own work assumed (based on copyright claims) (Public Domain) via Commons Wikimedia