W

Weak Acid

Weak acid: Ka << 1; pH = ½(pKa - log c)
Quick Reference
Formula / NotationWeak acid: Ka << 1; pH = ½(pKa - log c)
Also Known AsPartially dissociating acid, weak electrolyte acid, partial acid

What is Weak Acid?

An acid that only partially dissociates in aqueous solution, establishing an equilibrium between undissociated acid molecules and hydrogen ions. Characterized by a small Ka value. Examples include acetic acid (Ka = 1.8 × 10⁻⁵), carbonic acid, and hydrofluoric acid.

Formula & Notation

Weak acid: Ka << 1; pH = ½(pKa - log c)

Other Names / Synonyms: Partially dissociating acid, weak electrolyte acid, partial acid

Properties & Characteristics

A weak acid partially dissociates in aqueous solution, establishing an equilibrium with its conjugate base and hydrogen ions. Its acid dissociation constant Ka is small (typically 10⁻³ to 10⁻¹⁰). Common weak acids include acetic acid (Ka = 1.8×10⁻⁵), carbonic acid, and hydrofluoric acid. The pH of a weak acid solution is higher than that of a strong acid at the same concentration.

Uses & Applications

Weak acids are used in buffer solutions that resist pH change, important in biological systems and chemical manufacturing. Acetic acid (weak acid) is used as a food preservative and in the production of vinyl acetate. Carbonic acid regulates blood pH in the bicarbonate buffering system.

Safety Information

Weak acids are generally less immediately corrosive than strong acids but can still cause irritation and chemical burns with prolonged contact. Hydrofluoric acid, though weak, is exceptionally dangerous due to fluoride ion penetration into tissue.

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

Key Facts

Term Weak Acid
Formula Weak acid: Ka << 1; pH = ½(pKa - log c)
Synonyms Partially dissociating acid, weak electrolyte acid, partial acid

Frequently Asked Questions

An acid that only partially dissociates in aqueous solution, establishing an equilibrium between undissociated acid molecules and hydrogen ions. Characterized by a small Ka value. Examples include acetic acid (Ka = 1.8 × 10⁻⁵), carbonic acid, and hydrofluoric acid.

More "W" Terms

View all "W" terms →
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z