Definition of HYDROXIDE


Hydroxide is a chemical species represented by the chemical formula OH⁻. It serves as the anion formed by the dissociation of water molecules in aqueous solutions and plays a crucial role in acid-base chemistry, particularly as a base. As a noun, hydroxide refers to the negatively charged ion consisting of one oxygen atom bonded to one hydrogen atom.

As a noun, hydroxide denotes the OH⁻ ion, which consists of one oxygen atom and one hydrogen atom covalently bonded together. The hydroxide ion is formed when a water molecule (H2O) loses a proton (H⁺), resulting in the formation of a hydroxide ion (OH⁻) and a hydronium ion (H3O⁺). In aqueous solutions, hydroxide ions are present in varying concentrations depending on the pH of the solution, with higher concentrations corresponding to basic conditions.

Basic Properties: Hydroxide ions are characteristic of basic solutions, where they are responsible for the alkaline properties observed in aqueous solutions. In basic solutions, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) dissolved in water, the presence of excess hydroxide ions leads to an increase in pH, indicating higher alkalinity. The concentration of hydroxide ions in a solution determines its basicity level, with higher concentrations corresponding to higher pH values.

Acid-Base Reactions: In acid-base chemistry, hydroxide ions serve as strong bases capable of accepting protons (H⁺) from acidic species, leading to neutralization reactions. When hydroxide ions react with hydronium ions (H3O⁺) or other acidic substances, they form water molecules (H2O) and salts. This process, known as neutralization, results in the removal of acidic or basic properties from the solution, leading to the formation of a neutral solution.

Chemical Equilibrium: The concentration of hydroxide ions in aqueous solutions is governed by the principles of chemical equilibrium, as described by the base dissociation constant (Kb) for weak bases. In solutions containing weak bases or their conjugate acids, the concentration of hydroxide ions is determined by the balance between dissociation and association reactions. Understanding the behavior of hydroxide ions in solution is essential for predicting and controlling acid-base chemistry.

Industrial and Household Use: Hydroxide ions have numerous industrial and household applications, particularly in manufacturing processes, cleaning products, and water treatment. Sodium hydroxide (caustic soda) and potassium hydroxide (caustic potash) are commonly used in the production of soaps, detergents, and paper products. Additionally, hydroxide ions play a role in wastewater treatment and the regulation of pH levels in various industrial processes.

In conclusion, hydroxide ions are essential components of acid-base chemistry, serving as strong bases in aqueous solutions. Their presence determines the basicity level of a solution and plays a crucial role in neutralization reactions, chemical equilibrium, and various industrial processes. Understanding the behavior and properties of hydroxide ions is fundamental to the study of acid-base chemistry and their practical applications in diverse fields.

Examples of HYDROXIDE in a sentence

  • Hydroxide ions are formed when water molecules lose a hydrogen ion.
  • In basic solutions, the concentration of hydroxide ions is greater than the concentration of hydronium ions.
  • Many cleaning products contain hydroxide ions, which help to break down dirt and grease.
  • Hydroxide ions play a crucial role in neutralizing acids and balancing pH levels.
  • The chemical formula OH- represents the hydroxide ion.
  • Understanding the behavior of hydroxide ions is fundamental in chemistry.
  • Hydroxide ions can react with metals to form metal hydroxides.
  • The concentration of hydroxide ions in a solution can be measured using various analytical techniques.


The term hydroxide has a straightforward etymology that reflects its chemical composition and properties. Here’s a breakdown:

  • Hydro-: The prefix “hydro-” in “hydroxide” originates from the Greek word “hudōr,” meaning “water.” This prefix is commonly used in chemistry to denote compounds or elements related to water.
  • -Oxide: The suffix “-oxide” in “hydroxide” refers to a compound composed of oxygen and another element. In chemistry, oxides typically contain oxygen combined with another element or elements.
  • Hydroxide Composition: A hydroxide ion (OH-) consists of one oxygen atom bonded to one hydrogen atom. In chemical formulas, hydroxide ions are represented as OH-. Hydroxides are typically formed when a metal reacts with water or when an acid-base reaction occurs.
  • Etymology: The term “hydroxide” thus describes a chemical compound containing the hydroxide ion (OH-). It combines the prefix “hydro-” (meaning water) with the suffix “-oxide” (denoting a compound containing oxygen), reflecting the composition and properties of the hydroxide ion.

Overall, the etymology of hydroxide underscores its composition and its association with water and oxygen, as well as its importance in chemistry and various industrial processes.


  • Base
  • Alkali
  • Hydrate
  • Alkaline
  • Lye
  • Caustic
  • Alkaloid
  • Alkalinity


  • Acid
  • Acidic
  • Protonic
  • Acidulate
  • Acidicize
  • Acidify
  • Sour
  • Tart


  • Base
  • Alkaline
  • Chemical Compound
  • Ionic Compound
  • Corrosive
  • Acid
  • Solution
  • Reactivity

🌐 🇬🇧 HYDROXIDE in other languages

Terms of Use

Privacy & Cookies


Who We Are

Main Sections


Geographical Locations



Let´s Talk



® 2024 https://DefinitionGo.com