The exact chemical formula for ammonium dihydrogen orthophosphate is (NH₄)(H₂PO₄).
This compound, often recognized by its more common names such as monoammonium phosphate (MAP) or ammonium dihydrogen phosphate (ADP), is a key chemical used in various industries. The term "orthophosphate" specifically refers to the phosphate ion derived from orthophosphoric acid (H₃PO₄), which in this case is the dihydrogen phosphate ion (H₂PO₄⁻).
Understanding the Chemical Composition
Ammonium dihydrogen orthophosphate is an ionic compound formed from two distinct ions:
- Ammonium ion (NH₄⁺): A polyatomic cation formed when ammonia (NH₃) accepts a proton.
- Dihydrogen phosphate ion (H₂PO₄⁻): A polyatomic anion derived from orthophosphoric acid (H₃PO₄) after losing one proton. It's the "dihydrogen" because two hydrogen atoms remain attached to the phosphate group.
These two ions combine in a 1:1 ratio, resulting in a neutral compound with the formula (NH₄)(H₂PO₄).
Common Names and Synonyms
Due to its widespread use, ammonium dihydrogen orthophosphate is known by several names, each highlighting a different aspect of its chemical structure or application. Understanding these synonyms is crucial for identifying the compound across various contexts.
- Ammonium Dihydrogen Phosphate (ADP): This is a direct descriptor of its ionic components.
- Monoammonium Phosphate (MAP): Emphasizes that it contains one ammonium ion per phosphate group, distinguishing it from diammonium phosphate (DAP).
- Ammonium Dihydrogen Orthophosphate: The "ortho" prefix clarifies that the phosphate is in its most common form, derived from orthophosphoric acid.
Key Characteristics and Applications
Ammonium dihydrogen orthophosphate is a white, crystalline solid that is highly soluble in water. Its versatility stems from its nutrient content and chemical properties.
Summary of Key Information
| Feature | Description |
|---|---|
| Chemical Formula | (NH₄)(H₂PO₄) |
| Common Names | Monoammonium Phosphate (MAP), Ammonium Dihydrogen Phosphate (ADP) |
| Ions Present | Ammonium (NH₄⁺), Dihydrogen Phosphate (H₂PO₄⁻) |
| Appearance | White crystalline solid |
| Solubility | Highly soluble in water |
Primary Uses
- Fertilizer: It is a major component in multi-nutrient fertilizers, providing plants with both nitrogen (N) and phosphorus (P) in readily available forms. MAP is favored for its lower pH compared to other phosphate fertilizers, which can be beneficial in alkaline soils.
- Practical Insight: Often used as a starter fertilizer due to its high phosphorus content, promoting early root development.
- Fire Retardant: Used in dry chemical fire extinguishers and as an ingredient in fire-retardant coatings for wood and fabrics. When heated, it decomposes to release ammonia and phosphoric acid, which suppress combustion.
- Example: Applied to Christmas trees or wildlands as a preventative measure.
- Food Additive: Functions as a leavening agent in baked goods and as a buffering agent in various food products.
- Laboratory Reagent: Employed in analytical chemistry and as a component in various buffer solutions.
- Crystal Growth: Valued for its ability to form large, clear crystals, making it useful in optics and piezoelectric applications.
For further information on its properties and uses, you can refer to resources like PubChem's page on Monoammonium Phosphate.
