H

Hydroxide

OH⁻; Kb(NaOH) = complete dissociation; pKb = − (strong base)
Quick Reference
Formula / NotationOH⁻; Kb(NaOH) = complete dissociation; pKb = − (strong base)
Also Known AsOH⁻, hydroxide ion, caustic (NaOH/KOH colloquially), metal hydroxide

What is Hydroxide?

A compound containing the hydroxide ion (OH⁻) or the -OH group. Metal hydroxides are bases that dissociate to give OH⁻ ions in water. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are strong bases. The hydroxyl group (-OH) in organic molecules imparts polar character.

Formula & Notation

OH⁻; Kb(NaOH) = complete dissociation; pKb = − (strong base)

Other Names / Synonyms: OH⁻, hydroxide ion, caustic (NaOH/KOH colloquially), metal hydroxide

Properties & Characteristics

Hydroxide refers to the hydroxide ion (OH⁻) or compounds containing it. The OH⁻ ion is the characteristic species of Brønsted-Lowry bases in aqueous solution. It is formed by dissociation of metal hydroxides (NaOH → Na⁺ + OH⁻) or autoionisation of water (H₂O ⇌ H⁺ + OH⁻, Kw = 10⁻¹⁴ at 25°C). Metal hydroxides have ionic (NaOH, KOH) or covalent (Al(OH)₃) character depending on the metal's electronegativity.

Uses & Applications

Sodium hydroxide (caustic soda) is one of the most important industrial chemicals: used in paper manufacturing (kraft process), soap making (saponification), aluminium extraction (Bayer process), water treatment, textile processing, and as a drain cleaner. Calcium hydroxide (lime water) is used in water treatment and cement.

Safety Information

Strong metal hydroxides (NaOH, KOH, Ca(OH)₂) are severely corrosive. NaOH causes deep, penetrating chemical burns that are initially painless (unlike acid burns). Eye contact with NaOH solution can cause permanent blindness. Use face shield, chemical-resistant gloves, and a lab coat when handling.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Hydroxide
Formula OH⁻; Kb(NaOH) = complete dissociation; pKb = − (strong base)
Synonyms OH⁻, hydroxide ion, caustic (NaOH/KOH colloquially), metal hydroxide

Frequently Asked Questions

A compound containing the hydroxide ion (OH⁻) or the -OH group. Metal hydroxides are bases that dissociate to give OH⁻ ions in water. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are strong bases. The hydroxyl group (-OH) in organic molecules imparts polar character.

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