Phosphoric Acid is a mineral acid with the chemical formula H₃PO₄. It is a colorless, odorless, crystalline solid in its pure form, but it is commonly encountered as a clear liquid in solutions. Phosphoric acid is a triprotic acid, meaning it can donate three protons (H⁺) in aqueous solution. It is widely used in various industries, including fertilizer production, food processing, detergents, water treatment, and electronics manufacturing.
Phosphoric acid is a key compound in the production of phosphate salts, which are used in a variety of applications, and it also plays a significant role in acid-base reactions in chemistry and industry.
Properties of Phosphoric Acid:
- Molecular Formula: H₃PO₄
- Molar Mass: 97.99 g/mol
- CAS Number: 7664-38-2
- Functional Groups: Phosphate group (-PO₄³⁻) and hydroxyl groups (-OH).
- Reactivity:
- Phosphoric acid is a strong acid (though weaker than sulfuric acid or hydrochloric acid) that readily dissociates into hydrogen ions (H⁺) and dihydrogen phosphate ions (H₂PO₄⁻) in solution: H₃PO₄ → H⁺ + H₂PO₄⁻
- As a triprotic acid, it can further dissociate to form the monohydrogen phosphate (HPO₄²⁻) and phosphate ions (PO₄³⁻).
- Phosphoric acid is non-volatile, which makes it useful in applications requiring stability at high temperatures.
- It can react with bases to form phosphate salts.
- It can also chelate metal ions, making it useful in cleaning applications (e.g., rust removal).
- Appearance: Colorless, odorless (in pure form, but concentrated solutions may have a faint odor).
- Density: 1.88 g/cm³ (at 25°C).
- Melting Point: 42.35°C (108.23°F) (for the pure solid).
- Boiling Point: 158°C (316°F) (for concentrated solutions).
- Solubility:
- Soluble in water, forming a strongly acidic solution.
- Soluble in alcohol and glycerol.
Uses of Phosphoric Acid:
- Fertilizers: Widely used in the production of phosphate fertilizers.
- Food Industry: Used as an acidity regulator and flavoring agent (E338).
- Detergents: Used in the production of cleaning products and detergents.
- Water Treatment: Used to treat water and in rust removal.
- Pharmaceuticals: Used as a component in certain medical preparations.