M

Monoprotic Acid

Monoprotic acid: 1 ionisable H⁺; Ka = [H⁺][A⁻]/[HA]
Quick Reference
Formula / NotationMonoprotic acid: 1 ionisable H⁺; Ka = [H⁺][A⁻]/[HA]
Also Known AsMonobasic acid, single-proton acid, monoprotic acid, monobasic

What is Monoprotic Acid?

An acid that can donate only one proton (H⁺) per molecule in an acid-base reaction. Examples include hydrochloric acid (HCl), nitric acid (HNO₃), and acetic acid (CH₃COOH). Monoprotic acids have only one Ka value.

Formula & Notation

Monoprotic acid: 1 ionisable H⁺; Ka = [H⁺][A⁻]/[HA]

Other Names / Synonyms: Monobasic acid, single-proton acid, monoprotic acid, monobasic

Properties & Characteristics

A monoprotic acid can donate exactly one proton (H⁺) to a base. It has a single acid dissociation constant (Ka): HA ⇌ H⁺ + A⁻. Strong monoprotic acids (HCl, HBr, HI, HNO₃, HClO₄) fully dissociate in water. Weak monoprotic acids (CH₃COOH: Ka = 1.8 × 10⁻⁵; HF: Ka = 6.8 × 10⁻⁴; HCN: Ka = 6.2 × 10⁻¹⁰) partially dissociate. At the equivalence point in a strong base titration, the pH depends on whether it is strong or weak acid.

Uses & Applications

Monoprotic acid chemistry is the foundation of acid-base calculations: pH of buffer solutions (Henderson-Hasselbalch), titration curves, Ka determinations by potentiometry, and preparation of monoprotic acid calibration standards for pH meters.

Safety Information

All monoprotic acids, whether strong or weak, require appropriate PPE. HCN (Ka = 6.2 × 10⁻¹⁰) is a weak acid but acutely lethal because of CN⁻ toxicity, not acidity. Acid strength (Ka) does not correlate with toxicity — always assess chemical hazard independently from acid strength.

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

Key Facts

Term Monoprotic Acid
Formula Monoprotic acid: 1 ionisable H⁺; Ka = [H⁺][A⁻]/[HA]
Synonyms Monobasic acid, single-proton acid, monoprotic acid, monobasic

Frequently Asked Questions

An acid that can donate only one proton (H⁺) per molecule in an acid-base reaction. Examples include hydrochloric acid (HCl), nitric acid (HNO₃), and acetic acid (CH₃COOH). Monoprotic acids have only one Ka value.

More "M" Terms

View all "M" 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