Definition

Noun 1. A weak, unstable acid: A chemical compound that exists only in aqueous solution, formed when carbon dioxide (CO₂) dissolves in water (H₂O). Its chemical formula is often written as H₂CO₃. It is a key component in natural systems like blood, ocean chemistry, and carbonate rock formation.

Examples of Usage

• Noun:
  • The fizz in soda is caused by dissolved carbon dioxide, which forms carbonic acid.
  • Carbonic acid in rainwater slowly dissolves limestone, creating caves over long periods.
  • The body uses carbonic acid as an intermediate to transport and regulate carbon dioxide in the bloodstream.

Advanced Usage

• In equilibrium: Carbonic acid exists in a dynamic equilibrium with dissolved carbon dioxide and bicarbonate ions in solution: CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻.
  • The pH of a carbonated beverage is determined by the equilibrium of carbonic acid and its dissociation products.
• As a buffer: The carbonic acid/bicarbonate system acts as a crucial pH buffer in biological fluids, such as blood.
  • The carbonic acid-bicarbonate buffer system helps maintain a stable pH in human blood.

Variants and Related Words

• Carbonate (n): A salt or ester of carbonic acid (e.g., calcium carbonate, CaCO₃).
• Bicarbonate (n): An anion (HCO₃⁻) formed when carbonic acid loses one proton; a key component in the buffering system (e.g., sodium bicarbonate, NaHCO₃).
• Carbonic (adj): Relating to or derived from carbonic acid or carbon dioxide (e.g., carbonic anhydrase, an enzyme).

Synonyms

• H₂CO₃: The chemical formula used to represent carbonic acid.
• Aqueous carbon dioxide: A descriptive term emphasizing its formation.

Related Phrases and Concepts

• Carbonic acid gas: An archaic term for carbon dioxide, highlighting its role in forming the acid.
• Acid rain: While primarily caused by stronger acids like sulfuric and nitric acid, carbonic acid contributes to the natural acidity of rainwater.

Noun

1. a weak acid known only in solution; formed when carbon dioxide combines with water