Definition

Noun: * Hydroxyl ion: A negatively charged ion (anion) consisting of one oxygen atom covalently bonded to one hydrogen atom, with the chemical formula OH⁻. It is the defining ionic species of a base in the Arrhenius definition and is a fundamental component in acid-base chemistry, water autoionization, and many biochemical reactions.

Usage Examples

• Noun:
  • The presence of a hydroxyl ion in solution increases the pH, making it more basic.
  • In pure water, a small number of water molecules dissociate to form a hydrogen ion and a hydroxyl ion.
  • Sodium hydroxide (NaOH) dissociates in water to yield sodium ions and hydroxyl ions.

Advanced Usage

• "Hydroxyl ion concentration": A key parameter measured to determine the alkalinity or pH of a solution.
  • Scientists calculated the hydroxyl ion concentration to determine the exact pH of the lake water.
• In chemical equations, it is often represented by the formula OH⁻(aq) to denote its aqueous state.
  • The neutralization reaction can be summarized as: H⁺(aq) + OH⁻(aq) → H₂O(l).

Variants and Related Words

• Hydroxide (n): Often used interchangeably with "hydroxyl ion," though "hydroxide" can also refer to compounds containing the OH⁻ group (e.g., sodium hydroxide).
• Hydroxyl group (n): The uncharged functional group (-OH) found in organic molecules like alcohols and carboxylic acids. This is distinct from the charged hydroxyl ion.
• Hydroxyl radical (n): A neutral, highly reactive species (·OH) with an unpaired electron, important in atmospheric chemistry and radical reactions.

Synonyms

• Hydroxide ion: The most direct synonym.
• OH⁻: The chemical formula synonym.

Related Phrases

• Generation of hydroxyl ions: The process by which OH⁻ ions are produced, such as through the dissolution of a base.
  • The dissolution of potassium hydroxide leads to the generation of hydroxyl ions.
• Hydroxyl ion activity: A measure of the effective concentration of OH⁻ ions in a solution, accounting for inter-ion interactions.
  • In concentrated solutions, the hydroxyl ion activity differs from its formal concentration.

Noun

1. the anion OH having one oxygen and one hydrogen atom