Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Hydrogen sulfites, also known as bisulfites, are the conjugate base of sulfurous acid (H2SO3). They commonly exist in solution and are used as preservatives and reducing agents.
5 Must Know Facts For Your Next Test
Hydrogen sulfites have the chemical formula HSO3^-.
They can react with acids to release sulfur dioxide (SO2) gas.
In aqueous solutions, hydrogen sulfites typically exist in equilibrium with sulfurous acid (H2SO3).
Hydrogen sulfites are often used in food preservation due to their antimicrobial properties.
They act as reducing agents in various chemical reactions, preventing oxidation.
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Related terms
Sulfur dioxide: A colorless gas with a pungent odor, SO2 is a significant pollutant released by burning fossil fuels and also an intermediate in the production of sulfuric acid.
Sulfurous acid: $$\text{H}_2\text{SO}_3$$, a weak and unstable acid formed when sulfur dioxide dissolves in water and partially dissociates into bisulfite ions.
Reducing agent: A substance that donates electrons to another substance, thereby reducing its oxidation state; hydrogen sulfite acts as a reducing agent in many reactions.