acetic acid vs formic acid

[405513470]

Which would be the stronger acid CH3OOH in vinegar pKa=4.75 or HCOOH in ant venom pKa=3.75 and why?

[Trisha Mantri 3L]

I could be so wrong, but I think just by comparing the pKa values, you can tell that the HCOOH will be the stronger acid since it has the lower pKa.

[Erika Li 1E]

Stronger acids will have a higher Ka value as they dissociate more in solution. A higher Ka value corresponds to a lower pKa value. Since the pKa value of HCOOH is lower than that of CH3COOH, HCOOH is the stronger acid.

[Alena Zhu 2I]

The pKa formally calculated is the -log(Ka). By that logic, the lower the pKa value, the higher the Ka value would be and therefore the stronger the acid would be.

[Srikar_Chintala_1E]

The lower the pKa, the stronger the acid. You can kind of think of this concept as similar to pH. Hence, HCOOH would be a stronger acid.

[KyleNagasawaDisc3C_Chem 14B2022W_]

The strength of an acid can be largely viewed as an equilibrium phenomenon, such that stronger acids have a more stable conjugate base than an acid viewed as weaker. Between formic acid and acetic acid, examining the structural differences of their respective conjugate base helps make it clear why there is a pka difference (acid strength difference). The carboxylic acid is deprotonated in both species, and the negative charge is better stabilized by the H (Hydrogen) substituent than a simple CH3 (Methyl) substituent. As to rationalizing the mechanistic reason, methyl groups (via hyperconjugation of its CH sigma electron density) tend to donate electron density into the carbonyl, resulting in increased electron density (already increased by the deprotonated oxygen). As such, formic acid is a stronger acid (lower pKa) than acetic acid.

I hope this helps!

[405479701]

Since the lower the pKa value, the higher the Ka which means stronger acid than HCOOH in ant venom pKa=3.75 would be stronger.

[Heba Bounar 3K]

Hi! The ant venom would be the stronger acid because its pKa is lower than that of CH3OOH. The smaller the pKa, the larger the Ka value and the stronger the acid. Hope that helps!

[Yewon Jang 3K]

Hi! The smaller the pKa, the stronger the acid. Using this guideline, the ant venom would be a stronger acid because 3.75<4.75. Hope that helps!

[SuryaDham 3E]

formic acid, a small pKa indicates a higher Ka, which means more dissociation.