I understand that we can look at the pKa values and figure this out quite easily, but I was wondering how we could tell without referring to pKa values :) Thanks to all who reply :)
2006-10-14 22:56:25 · 3 answers · asked by Sci-Buff 4 in Science & Mathematics ➔ Chemistry
Because the CH3- (methyl) group in CH3COOH causes an +I (positive induction) effect: It repels electrons and so lessens the polarity of the O-H bond in -COOH group. As a result CH3COOH is a weaker acid (Ka = 1.8*10-5 at 25 oC) than HCOOH (Ka = 1.8*10-4 at 25 oC)
2006-10-14 23:44:55 · answer #1 · answered by Dimos F 4 · 1⤊ 0⤋
I've rated the answers already.
PS:
The acidity of a substance is NOT determined by the concentration.
A very diluted hydrochloric acid has a pH value of 1.
The formic acid (a.k.a. methanoic acid) is CH2O2. So it has two hydrogen atoms, essential as determinants for acidity of that particular substance; whereas ethanoic acid is CH3COOH, with only a hydrogen atom. Therefore, in normal circumstances (substances not denatured), formic acid is more acidic than ethanoic acid.
2006-10-15 06:54:12 · answer #2 · answered by Anonymous · 0⤊ 0⤋
It is a better proton donor.
(according to the Brønsted-Lowry definitiion of an acid)
But depends on the concentration/molarity. Think, very dilute formic acid cannot be more acidic the concentrated acetic acid.
2006-10-15 06:02:10 · answer #3 · answered by nnjamerson 3 · 0⤊ 1⤋