Which is more acidic acetic acid or propionic acid?

Answer 1

This is because acetic acid also known as CH3COOH more easily donate an H+ ion to a solution. This in turn to due to the electronegativity of the 2 oxygen atoms which pull the electron density away from the hydrogen making it have more of a positive charge and therefore be more likely to come off in a solution

Answer 2

Acetic acid, or ethanoic acid, is more acidic. You can remember a simple rule: The fewer the number of carbon atoms in a carboxylic acid, the more acidic it is. Ethanoic acid has 2 carbon atoms, whereas propanoic acid has 3.

If you want an explanation, here it is:

Alkyl groups(CH3-, CH3CH2-, CH3CH2CH2-, etc) tend to push electrons away to nearby groups, i.e. they are electron donors. Imagine a carboxylic, R-COOH, where -R is the alkyl group and -COOH is the carboxyl group. Now if this acid dissolves in water, some of it gets converted to R-COO- and H+ ions(The more the number of H+ ions, the more acidic.). R had a large number of carbon atoms(meaning a larger alkyl group), the more electrons it donates to the -COO- group. This heavily polarizes the group, and since any build-up of charge would make it less stable, a lot fewer of these ions would exist. So simply, the smaller the alkyl group, the ions would be more stable, resulting in a larger number of these ions. Thus, it would be more acidic. If you do not understand, please message me.