Is Formic Acid (HCOOH) a Strong or Weak Acid?
Is Formic Acid (HCOOH) a strong or weak acid?
Formic acid is the simplest carboxylic acid. It is stronger than acetic acid because the methyl group in acetic acid is electron-donating, which destabilizes the conjugate base.
| Formula | HCOOH |
| Name | Formic Acid |
| Category | Weak acid |
| pKa | 3.75 |
| Conjugate | Formate ion (HCOO⁻) |
| Key Concept | Simplest carboxylic acid |
Definition
Formic acid (found in ant stings) is the simplest carboxylic acid with just H-COOH. It is a weak Bronsted-Lowry acid.
Acidic Proton / Active Site
The -COOH hydrogen is the acidic proton. The C-H hydrogen (on the aldehyde side) is not acidic.
Conjugate Pair
HCOOH -> HCOO- + H+. The formate ion is stabilized by resonance (charge shared between two oxygens), similar to acetate.
Strength Classification
pKa = 3.75. Formic acid is stronger than acetic acid (pKa 4.76) because the methyl group in acetic acid donates electron density, which destabilizes the negative charge on the conjugate base.
See acidic protons, conjugate base overlays, and pKa labels on interactive 3D molecules.
Explore Formic Acid's Acid-Base Properties in 3DRelated Topics
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