Is Acetic Acid (CH₃COOH) a Strong or Weak Acid?
Is Acetic Acid (CH₃COOH) a strong or weak acid?
Acetic acid is the classic weak acid - it only partially dissociates in water (~1.3% at 1M). Its conjugate base (acetate) is stabilized by resonance, where the negative charge is shared between two oxygen atoms.
| Formula | CH₃COOH |
| Name | Acetic Acid |
| Category | Weak acid |
| pKa | 4.76 |
| Conjugate | Acetate ion (CH₃COO⁻) |
| Key Concept | Classic weak acid, carboxyl group |
Definition
Acetic acid (vinegar) is a Bronsted-Lowry acid that partially donates its carboxyl proton to water. Only about 1 in 100 molecules dissociates at typical concentrations.
Acidic Proton / Active Site
The acidic proton is the one on the -COOH group (the carboxyl hydrogen), not the methyl (-CH3) hydrogens. The C-H bonds are not acidic because carbon is not electronegative enough.
Conjugate Pair
Acetic acid donates its -OH proton to become acetate (CH3COO-). The acetate ion is stabilized by resonance - the negative charge is delocalized across both oxygen atoms.
Strength Classification
With a pKa of 4.76, acetic acid is a weak acid. It dissociates partially (Ka = 1.8 x 10^-5). The resonance stabilization of acetate explains why it is still reasonably acidic despite being "weak."
See acidic protons, conjugate base overlays, and pKa labels on interactive 3D molecules.
Explore Acetic Acid's Acid-Base Properties in 3DRelated Topics
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