Acetic Acid Dissociation in Water

CH3COOH + H2O ⇌ CH3COO− + H3O+

Overview

Acetic acid partially dissociates in water with Ka = 1.8 × 10⁻⁵, meaning only about 1.3% of molecules ionize in a 1 M solution. This equilibrium is the archetypal weak acid dissociation used to teach acid ionization constants, ICE tables, and the relationship between Ka and pH.

Participants

Role Substance Coefficient State
Reactant Acetic Acid CH₃COOH 1 (aq)
Reactant Water H₂O 1 (l)

Everyday Example

Vinegar (5% acetic acid) has a pH around 2.4 because the weak acid only partially ionizes, unlike strong acids that fully dissociate.

Industrial Importance

Understanding weak acid equilibria is essential for formulating buffer solutions, pharmaceutical preparations, and controlling pH in fermentation processes.

Properties

Type
Acid-Base
Reversible
Yes
Energy
Endothermic
ΔH
0.4 kJ/mol

Related Reactions

Acetic Acid and Sodium Acetate Buffer System Acetic Acid and Sodium Hydroxide Neutralization Aluminum Chloride and Chloride Ion (Lewis Acid-Base) Aluminum Hydroxide as Amphoteric Acid with NaOH Aluminum Hydroxide as Amphoteric Base with HCl Ammonia and Ammonium Chloride Buffer System Ammonia and Hydrochloric Acid Ascorbic Acid and Sodium Hydroxide Barium Hydroxide and Ammonium Thiocyanate (Endothermic) Benzoic Acid and Sodium Hydroxide

Frequently Asked Questions

What is the equation for Acetic Acid Dissociation in Water?
The balanced equation is: CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺.
What type of reaction is Acetic Acid Dissociation in Water?
Acetic Acid Dissociation in Water is a acid-base reaction. It is reversible under certain conditions.
Is Acetic Acid Dissociation in Water exothermic or endothermic?
Acetic Acid Dissociation in Water is endothermic (absorbs energy). The enthalpy change (ΔH) is 0.4 kJ/mol.