6A.3: Differentiating between acids and bases

[JamieVu_2C]

How do you know if a molecule accepts H+ from H2O or donates H+ to H2O without looking at a table? For example, the question asks to Write the chemical equations for the proton transfer equilibria of the following acids in aqueous solution and identify the
conjugate acid–base pairs in each case: (d) HCOOH.

How do you know that HCOOH releases a proton, giving the equation: HCOOH + H2O ->/<- H3O+ + HCO2-?
Why can't it HCOOH accept a proton to give the equation: HCOOH + H2O ->/<- OH- + HCOOH2? How would you be able to differentiate?

[MingdaH 3B]

It's relatively simple to look at the lewis structure of a molecule and see whether or not it'll donate / accept protons for some molecules.

[ishaa Diwakar 4E]

In this case, the question tells you that this molecule is an acid, and this will usually happen if they are asking about an amphoteric molecule. However, you can determine whether it is an acid or base depending on the molecule. With -COOH molecules, they will usually either be neutral charge or negatively charged from donating a H+, which is why you probably won't see it acting as a base and becoming -COOH2.