CHEMISTRY COMMUNITY

Why is formic acid a stronger acid than acetic acid? Formic acid has a -CH3 group and acetic acid is HCOOH.

We know that an acid is considered stronger if it can lose a hydrogen easily to a base. Because the CH3 contributes electron density towards the O-H bond, it makes it harder to remove the H and makes acetic acid a weaker acid than formic acid. Basically, formic acid is stronger because CH3 in acetic acid is electron donating.